Adaptive method for handling inkjet printing media

FIELD OF THE INVENTION

The present invention relates generally to printing mechanisms, and more particularly to an adaptive method for handling inkjet printing media to accurately move and print upon individual sheets of media in a printzone of an inkjet printing mechanism.

BACKGROUND OF THE INVENTION

Inkjet printing mechanisms use cartridges, often called “pens,” which shoot drops of liquid colorant, referred to generally herein as “ink,” onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).

To clean and protect the printhead, typically a “service station” mechanism is mounted within the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as “spitting,” with the waste ink being collected in a “spittoon” reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead.

To print an image, the printhead is scanned back and forth across a printzone above the sheet, with the pen shooting drops of ink as it moves. By selectively energizing the resistors as the printhead moves across the sheet, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text). The nozzles are typically arranged in one or more linear arrays. If more than one, the two linear arrays are usually located side-by-side on the printhead, parallel to one another, and perpendicular to the scanning direction. Thus, the length of the nozzle arrays defines a print swath or band. That is, if all the nozzles of one array were continually fired as the printhead made one complete traverse through the printzone, a band or swath of ink would appear on the sheet. The width of this band is known as the “swath width” of the pen, the maximum pattern of ink which can be laid down in a single pass. Any variation in the media-to-printhead spacing along the length of the nozzle array may yield visually acceptable deviations in print quality. There are a variety of different problems that make it difficult to always achieve consistent and accurate media-to-printhead spacing.

As a preliminary matter, there is a term of art used by inventors skilled in this art that will speed the reading if used herein, and it is “pen-to-paper spacing,” often abbreviated as “PPS” or “PPS spacing.” In the English language of the inventor, “pen-to-paper spacing” or “PPS” is easier to pronounce than the more technically explicit term “media-to-printhead spacing,” and for this reason “pen-to-paper spacing” or “PPS” are used herein. During prototype testing and development, inventors use vast amounts of media, so the most plentiful and economical media, plain paper is used. Indeed, the short-hand term “pen-to-paper spacing” is a logical selection of terminology, although it must be understood that as used herein, this term encompasses all different types of media, unless specified otherwise in describing a particular type of media. Thus, “pen-to-paper spacing” (PPS) defines the spacing between the inkjet cartridge printhead and the printing surface of the media, which may be any type of media, such as plain paper, specialty paper, card-stock, fabric, transparencies, foils, mylar, etc. Having dispensed with preliminary matters, the discussion of the problems encountered in this art in maintaining an accurate PPS now continues.

First, there is a tendency for some graphic and photographic type images to saturate the media with ink, causing an undesirable effect known in the art as “cockle.” The term “cockle” refers to the tendency of media, such as paper, to uncontrollably bend or buckle as the wet ink saturates the fibers of the media and causes them to expand. This buckling or cockling causes the media to uncontrollably bend either downwardly away from the printhead, or upwardly toward the printhead, with either motion undesirably changing the PPS spacing and leading to poor print quality. Moreover, upward buckling may be extreme enough to cause the media to actually contact the printhead, which may clog a nozzle and/or smear ink on the media, damaging the image.

Second, there are variations in the thickness of the print media which also affect the PPS spacing. For example, envelopes, poster board and fabric are typically thicker than plain paper or a transparency. The thicker media decreases the spacing from the printhead to the printing surface, and as with cockle, in the worst case, this reduced spacing could lead to contact of the printhead with the media, possibly damaging either the printhead or the image. Furthermore, these various media thicknesses also offer challenges to an automatic feed system, which must pick the top sheet from a stack of media, and then accurately feed it into the print zone.

One earlier media handling system tried to accommodate thicker envelopes, using a width sensor that detected media narrower than about 12 cm (4.5 in). Upon detecting this narrow media, a mechanical arm opened an inlet port on the media handling system to a much wider gap than normal to prevent ink smear on the envelope. Unfortunately, the assumption envelope was being printed just because the media width was narrow completely ignored the printing of postcards by a user. Thus, when printing postcards the print quality was severely degraded by the greater PPS spacing. Moreover, there was no provision for the user to defeat this mechanical widening of the gap when postcards where printed.

The earlier media handling systems lacked any ability to adjust the PPS spacing, other than adjustments made during initial assembly at the factory. Manufacturing adjustments are required to accommodate the large number of parts whose various tolerances accumulate and lead to a large degree of variability around the nominal spacing value. One earlier method involved the rotation of a helical cam, and the tightening of an adjustment screw to fasten the cam in place. Unfortunately, errors may occur during manufacturing, for example, from human error in reading a dial indicator measuring device or other display. Furthermore, the act of tightening the adjustment screw caused various mechanical stresses on the component parts. Additionally, physical access to the adjustment cam and screw had to be provided for in the mechanical design of the printer. Furthermore, this manual adjustment may occur when the printing mechanism was only partially assembled, so the addition of other parts to the printer mechanism could warp the spacing adjustment. Any of these inaccuracies in the PPS spacing occurring during manufacture could result in degraded print quality for the entire life of the printer.

Beyond the PPS spacing issue, the earlier media handling systems have suffered a variety of other disadvantages. Many of these earlier systems required a multitude of separate parts, for picking sheets of media from a stack, feeding the media through the print zone, and then depositing the printed sheet in an output tray. For example, one earlier design required 15-17 separate parts, which contributed significantly to the overall complexity and cost of the printing mechanism, not only in the actual cost of the parts themselves, but also in labor time required for their assembly. Additionally, many of these earlier media handling systems used spring loaded parts, which at some point during printing would snap the parts back into place; a noisy operation indeed. Most customers in the home or office environment want quieter printers, so this noise from return springs and the associated noise of the parts colliding with one another in the earlier designs was undesirable.

Given the criticality of the pen-to-paper spacing, the desire for higher print quality, which typically implies a closer spacing, as well as the ability to handle different types of media (e.g., envelopes, plain paper, card stock, etc.) and different images (e.g., text vs. graphic vs. photographic), it would be desirable to adjust the PPS spacing automatically during use. Such an automatic adjustment would also aid manufacturing, particularly if it could be implemented in a media handling system having fewer and quieter components.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an adaptive method of printing using an inkjet printing mechanism having a printhead that prints on media in a printzone is provided as including the step of providing a drive motor and a spacing adjuster. Also in the providing step, a media support member is provided, with the support member defining a printhead-to-media spacing in the printzone between the printhead and media when supported thereby. In a coupling step, the motor is operatively coupled to the support member using the spacing adjuster. Following the coupling step, in an adjusting step, the printhead-to-media spacing is selectively adjusted by the driving spacing adjuster with the motor.

According to another aspect of the invention, a method is provided of accommodating manufacturing tolerance variations accumulated during assembly of an inkjet printing mechanism having a printhead that prints on media in a printzone. The method includes the step of assembling a media handling system for an inkjet printing mechanism from plural components each having unique dimensions ranging between maximum and minimum limits. These components include a printhead, a drive motor, a spacing adjuster, a media support member that defines a printhead-to-media spacing in the printzone between the printhead and media when supported thereby. When assembled, the system has a manufactured printhead-to-media spacing. In a measuring step, the manufactured printhead-to-media spacing is measured, then compared in a comparing step, with a nominal value for printhead-to-media spacing to determine a spacing difference therebetween. In a determining step, the amount to drive the motor that corresponds to the determined spacing difference is determined, for instance, by referring to a look-up table correlating these values. In a coupling step, the motor is operatively coupled to the support member using the spacing adjuster. Following the coupling step, in an adjusting step, the printhead-to-media spacing is selectively adjusted by the driving spacing adjuster with the motor for the determined amount to arrive at an adjusted spacing.

According to a further aspect of the invention, an adaptive method of printing using an inkjet printing mechanism having a printhead that prints on media in a printzone is provided as including the step of providing a drive motor and a spacing adjuster. Also in the providing step, a media support member is provided, with the support member defining a printhead-to-media spacing in the printzone between the printhead and media when supported thereby. The providing step also includes providing a controller having a memory portion with a tolerance adjust value stored therein. In a selecting step, a desired printhead-to-media spacing is selected, along with an amount to drive the motor that corresponds to the desired printhead-to-media spacing. In a summing step, the tolerance adjust value and the selected amount to drive the motor are summed together to arrive at a total motor drive value. In a coupling step, the motor is operatively coupled to the support member using the spacing adjuster. Following the coupling step, in an adjusting step, the printhead-to-media spacing is selectively adjusted by the driving spacing adjuster with the motor for the total motor drive value.

An overall goal of the present invention is to provide an adaptive method for handling media to accurately move individual sheets of media and envelopes through a printzone of an inkjet printing mechanism, as well as long Z-folded strips of banner media.

Another goal of the present invention is to provide an adaptive method of adjusting printhead-to media spacing that may be automatically implemented, not only during initial assembly, but also during operation to meet the printing needs of different types of media and images.

A further goal of the present invention is to provide an economical method of operating an inkjet printing mechanism which optimizes the print quality of an image and which operates quietly, with minimal user intervention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a fragmented perspective view of one form of an inkjet printing mechanism employing one form of an adaptive media handling system of the present invention.

FIG. 2

is a fragmented perspective view of the adaptive media handling system of

FIG. 1

, shown removed from the casing of the printing mechanism.

FIG. 3

is a fragmented, enlarged perspective view taken along line

3

—

3

of

FIG. 2

, showing the out-board side of one form of a media drive mechanism of the present invention.

FIG. 4

is a fragmented, enlarged perspective view taken along line

4

—

4

of

FIG. 2

, showing the in-board side of one form of a media drive mechanism of the present invention.

FIG. 5

is an enlarged perspective, partially exploded view of a portion of the in-board side of the media drive mechanism, with one component (

100

) shown reduced in size and rotated in the view around a vertical axis to better illustrate its coupling with the other components.

FIG. 6

is a fragmented, enlarged front elevational view taken along line

6

—

6

of

FIG. 2

, also showing a portion of the printhead carriage engaging a shift lever member of the media drive mechanism.

FIGS. 7-14

are out-board side elevational views, taken generally along line

7

—

7

of

FIG. 6

, but with the shift lever, drive motor and several of the drive gears removed for clarity, and more specifically:

FIG. 7

shows the drive mechanism in a kick position for ejecting media, which also corresponds to a rest position and a start position for picking fresh media;

FIG. 8

shows a transition portion of operation of the drive mechanism, where the printhead carriage engages the shift lever (not shown) to begin the media pick routine;

FIG. 9

shows the drive mechanism beginning to pick a sheet of media;

FIG. 10

shows the drive mechanism during an intermediate stage of picking the sheet;

FIG. 11

shows the drive mechanism during a final stage of picking the sheet, prior to transitioning to the initial position of

FIG. 7

;

FIG. 12

shows the drive mechanism in an initial position for beginning normal printing, for instance on plain paper;

FIG. 13

shows the drive mechanism during a media to printhead spacing adjustment portion of operation; and

FIG. 14

shows a transition portion of operation of the drive mechanism.

FIG. 15

is a flow chart illustrating one manner of adjusting the adaptive media handling system of

FIG. 1

during initial assembly of the printing mechanism at the manufacturing facility.

FIGS. 16-19

are portions of a flow chart illustrating one manner of operating the adaptive media handling system of

FIG. 1

, including a media pick routine (FIG.

16

), a PPS adjust routine (FIG.

17

), a printing routine and media discharge routine (FIGS.

18

and

19

).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1

illustrates an embodiment of an inkjet printing mechanism, here shown as an inkjet printer

20

, constructed in accordance with the present invention, which may be used for printing for business reports, correspondence, desktop publishing, and the like, in an industrial, office, home or other environment. A variety of inkjet printing mechanisms are commercially available. For instance, some of the printing mechanisms that may embody the present invention include plotters, portable printing units, copiers, cameras, video printers, and facsimile machines, to name a few. For convenience the concepts of the present invention are illustrated in the environment of an inkjet printer

20

.

While it is apparent that the printer components may vary from model to model, the typical inkjet printer

20

includes a chassis

22

surrounded by a housing or casing enclosure

24

, typically of a plastic material. Sheets of print media are fed through a print zone

25

by an adaptive print media handling system

26

, constructed in accordance with the present invention. The print media may be any type of suitable sheet material, such as paper, card-stock, transparencies, mylar, and the like, but for convenience, the illustrated embodiment is described using paper as the print medium. The print media handling system

26

has a feed tray

28

for storing sheets of paper before printing. A series of motor-driven paper drive rollers described in detail below (

FIGS. 2-13

) may be used to move the print media from tray

28

into the print zone

25

for printing. After printing, the sheet then lands on a pair of retractable output drying wing members

30

, shown extended to receive a the printed sheet. The wings

30

momentarily hold the newly printed sheet above any previously printed sheets still drying in an output tray portion

32

before retracting to the sides to drop the newly printed sheet into the output tray

32

. The media handling system

26

may include a series of adjustment mechanisms for accommodating different sizes of print media, including letter, legal, A4, envelopes, etc., such as a sliding length adjustment lever

34

, and an envelope feed slot

35

.

The printer

20

also has a printer controller, illustrated schematically as a microprocessor

36

, that receives instructions from a host device, typically a computer, such as a personal computer (not shown). Indeed, many of the printer controller functions may be performed by the host computer, by the electronics on board the printer, or by interactions therebetween. As used herein, the term “printer controller

36

” encompasses these functions, whether performed by the host computer, the printer, an intermediary device therebetween, or by a combined interaction of such elements. The printer controller

36

may also operate in response to user inputs provided through a key pad (not shown) located on the exterior of the casing

24

. A monitor coupled to the computer host may be used to display visual information to an operator, such as the printer status or a particular program being run on the host computer. Personal computers, their input devices, such as a keyboard and/or a mouse device, and monitors are all well known to those skilled in the art.

A carriage guide rod

38

is supported by the chassis

22

to slideably support an inkjet carriage

40

for travel back and forth across the print zone

25

along a scanning axis

42

defined by the guide rod

38

. One suitable type of carriage support system is shown in U.S. Pat. No. 5,366,305, assigned to Hewlett-Packard Company, the assignee of the present invention. A conventional carriage propulsion system may be used to drive carriage

40

, including a position feedback system, which communicates carriage position signals to the controller

36

. For instance, a carriage drive gear and DC motor assembly may be coupled to drive an endless belt secured in a conventional manner to the pen carriage

40

, with the motor operating in response to control signals received from the printer controller

36

. To provide carriage positional feedback information to printer controller

36

, an optical encoder reader may be mounted to carriage

40

to read an encoder strip extending along the path of carriage travel.

The carriage

40

is also propelled along guide rod

38

into a servicing region, as indicated generally by arrow

44

, located within the interior of the casing

24

. The servicing region

44

houses a service station

45

, which may provide various conventional printhead servicing functions. For example, a service station frame

46

may hold a conventional or other mechanism that has caps to seal the printheads during periods of inactivity, wipers to clean the nozzle orifice plates, and primers to prime the printheads after periods of inactivity. Such caps, wipers, and primers are well known to those skilled in the art. A variety of different mechanisms may be used to selectively bring the caps, wipers and primers (if used) into contact with the printheads, such as translating or rotary devices, which may be motor driven, or operated through engagement with the carriage

40

. For instance, suitable translating or floating sled types of service station operating mechanisms are shown in U.S. Pat. Nos. 4,853,717 and 5,155,497, both assigned to the present assignee, Hewlett-Packard Company. A rotary type of servicing mechanism is commercially available in the DeskJet® 850C and 855C color inkjet printers, sold by Hewlett-Packard Company, the present assignee. In

FIG. 1

a spittoon portion

48

of the service station is shown as being defined, at least in part, by the service station frame

46

.

In the print zone

25

, the media sheet receives ink from an inkjet cartridge, such as a black ink cartridge

50

and/or a color ink cartridge

52

. The cartridges

50

and

52

are also often called “pens” by those in the art. The illustrated color pen

52

is a tri-color pen, although in some embodiments, a set of discrete monochrome pens may be used. While the color pen

52

may contain a pigment based ink, for the purposes of illustration, pen

52

is described as containing three dye based ink colors, such as cyan, yellow and magenta. The black ink pen

50

is illustrated herein as containing a pigment based ink. It is apparent that other types of inks may also be used in pens

50

,

52

, such as paraffin based inks, as well as hybrid or composite inks having both dye and pigment characteristics.

The illustrated pens

50

,

52

each include reservoirs for storing a supply of ink. The pens

50

,

52

have printheads

54

,

56

respectively, each of which have an orifice plate with a plurality of nozzles formed therethrough in a manner well known to those skilled in the art. The illustrated printheads

54

,

56

are thermal inkjet printheads, although other types of printheads may be used, such as piezo-electric printheads. The printheads

54

,

56

typically include substrate layer having a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed to eject a droplet of ink from the nozzle and onto media in the print zone

25

. The printhead resistors are selectively energized in response to enabling or firing command control signals, which may be delivered by a conventional multi-conductor strip (not shown) from the controller

36

to the printhead carriage

40

, and through conventional interconnects between the carriage and pens

50

,

52

to the printheads

54

,

56

.

Adaptive Media

Handling System

FIG. 2

shows an adaptive media transport system

60

, constructed in accordance with the present invention, which forms a portion of the print media handling system

26

. The adaptive transport system

60

pulls a sheet of print media from the feed tray

28

, delivers it to the print zone

25

, and after printing deposits the sheet on the output drying wings

30

, shown in FIG.

1

. The adaptive system

60

includes several components attached to the chassis

22

, including a pressure plate

62

which is pivoted along a front edge to the chassis

22

by a hinge member

64

. A rear edge of the pressure plate

62

is upwardly biased away from the chassis

22

by a compression spring member

65

. One or more compression springs

65

may be used between the pressure plate

62

and the chassis

22

, although for the purposes of illustration only one such spring is shown. Moreover, it is apparent that leaf springs or other biasing devices may be used to urge the rear edge of the pressure plate

62

upwardly and away from the lower portion of chassis

22

.

The chassis

22

has two opposing upright walls

66

and

68

. The transport system

60

includes a media advance or drive roller system

70

suspended by an axle

72

between the chassis walls

66

and

68

. The roller system

70

preferably includes three elastomeric drive rollers or tires

74

,

75

and

76

. Two of the drive tires

75

,

76

are clustered together along one edge of the print zone, adjacent the envelope feed slot

35

(

FIG. 1

) to evenly pull a business-sized envelope through the feed slot and into the print zone

25

.

In a preferred embodiment, the drive roller system

70

also includes a pick tire

78

, which is preferably of a softer durometer elastomer, and of a slightly smaller diameter than the drive tires

74

-

76

. The drive tires

74

-

76

and the pick tire

78

may be of the same or different type of elastomer, such as of a rubber or equivalent material known to those skilled in the art, with one preferred elastomer being ethylene polypropylene diene monomer (EPDM) for both drive and pick tires

74

-

78

. The durometer of the drive tires

74

-

76

may be selected from the range of 45-70, or more preferably 55-65, with a preferred nominal value being 60, all measured on the Shore A scale. The softer durometer of the pick tire

78

may be selected from the range of 25-45, or more preferably 30-40, with a preferred nominal value being about 35, also measured on the Shore A scale. Use of a softer durometer pick tire

78

allows for more frictional forces to be developed between the media and the outer periphery of the pick tire

78

, with these additional frictional forces assisting in pulling the media into the transport system

60

. By locating the pick tire

78

between the envelope drive rollers

75

,

76

, the pick tire assists not only in picking sheets of paper from the input tray

28

, but also in picking and feeding envelopes received through slot

35

.

Also suspended in part from the chassis side wall

68

, and running parallel to the drive system axle

72

, is a media support member or pivot

80

. The pivot

80

has a leading media support edge

82

, which is adjustable in height as indicated by the double-headed arrow Z in a manner described further below. Extending outwardly from the left side of pivot

80

(as seen in

FIG. 2

) are two cam follower members, such as, a pick cam follower pin

84

, and a media spacing adjust cam follower or PPS adjust pin

86

.

A drive motor

88

is attached to an outboard side of the chassis upright wall

66

. As shown in

FIGS. 2-6

, the motor

88

forms a portion of a drive system or mechanism

90

. The drive mechanism

90

powers the drive roller system

70

, the pressure plate

62

, and the pivoting media support

80

, all of which form portions of the adaptive media transport system

60

. The motor

88

has an output shaft

91

that supports a pinion gear

92

. The pinion gear

92

engages and drives a roller gear

94

, which is coupled to the drive roller axle

72

. An intermediate or transfer gear

96

is also coupled to the axle

72

. As described further below, the transfer gear

96

may be selectively placed in engagement with a cam drive gear

98

to drive an adaptive spacing adjust member, such as a dual sided cam member

100

. A cam support

102

extends upwardly from the chassis

22

to support a cam axle

104

. Both the cam

100

and the cam gear

98

ride on axle

104

.

The cam gear

98

is designed to drive the cam

100

during paper pick, discharge, and pen-to-paper (PPS) spacing adjustment portions of operation. As shown in detail in

FIG. 5

, the cam gear

98

has a large outer rim having teeth

105

around the majority of its periphery. A raised land

106

is substantially concentric with the toothed outer rim

105

and extends inboardly therefrom. In the view of

FIG. 5

, to better illustrate the interaction of the cam gear

98

and cam

100

, cam

100

is shown removed from shaft

104

, as indicated by the line of alternating long and short dashes. Moreover, the cam

100

is shown rotated counterclockwise from its position in operation, as indicated by the curved arrow

108

, with this rotation being around a vertical axis

109

. For convenience, the cam

100

is shown reduced in size by approximately 50-60% with respect to the remaining components in

FIG. 5

, but is clearly shown in uniform relative proportions in all of the other figures.

The adaptor cam

100

has a series of splines

110

extending outwardly from a boss or sleeve portion

112

. The sleeve

112

and splines

110

fit within a bore

114

having a series of grooves

116

formed along the interior of the cam gear

98

. The sleeve

112

has a bore

118

which rides along axle

104

. A compression spring

120

is coiled around the raised land

106

of cam gear

98

and rides in part against a land portion

122

of cam

100

.

Two guide ribs

124

and

126

are located along the interior surface of the chassis wall

66

. As shown in

FIG. 5

, a pair of pivot pins, such as pin

128

, extend inwardly from the ribs

124

and

126

to support a shift lever

130

. As shown in

FIG. 3

, the outboard side of the cam gear

98

includes a raised disk portion

132

, which is received within a U-shaped channel

134

defined by a lower extremity

136

of the shift lever

130

.

FIG. 6

shows an upper portion

138

of lever

130

being selectively engaged by a portion of the printhead carriage

40

, to move the lever from the dashed line position to the solid line position (also shown in FIG.

4

). The upper and lower portions

136

,

138

of lever

130

are not coplanar, but instead are joined together at an obtuse angle, for instance, such as shown in FIG.

6

. Thus, when the lever upper portion

138

is moved to the left in the views, the lever

130

pivots at pins

128

to force the lever lower portion

136

against the cam gear

98

. Pushing the cam gear

98

toward the cam

100

compresses spring

120

, and causes full engagement of the total width of teeth

105

with the teeth of the transfer gear

96

. As the carriage

40

moves away from lever

130

, for instance to print or to service the printheads

54

,

56

, the tension between the teeth of gears

96

and

105

maintains compression of the spring and full engagement of the gears as shown in solid lines in FIG.

6

.

As shown in

FIG. 5

, a chordal cut has been made through a portion of the cam gear teeth

105

, leaving a lost motion land

140

and a narrow track of teeth

142

adjacent thereto, having a width A as indicated in FIG.

5

. The frictional forces between the narrow teeth

142

and the teeth of transfer gear

96

are not sufficient to maintain compression of spring

120

. Without assistance by lever

130

, the force of spring

120

pushes the cam gear

98

axially in an outboard direction, to the position indicated by dashed lines in

FIG. 6

, so the teeth of gear

96

rotate over the lost motion land region

140

and the cam gear

98

remains in a fixed rotational position. Thus, in this lost motion region, the cam gear

98

and cam

100

are uncoupled from the drive motor

88

. To rotate the cam

100

in this lost motion region, the carriage

40

must push lever

130

to engage the narrow teeth

142

with the transfer gear. Thus, the total travel of the cam gear

98

when pushed away from cam

100

by spring

120

is slightly greater than the width A of teeth

142

. Use of this lost motion region and the narrow band of teeth

142

are described in greater detail below.

The relative tooth length of the spline gear

110

and the spline gear receiving grooves

116

are selected with respect to the width A of teeth

142

, so that when the cam gear

98

is held in a fixed position, the cam

100

is also held in the same relative fixed position. When the transfer gear

96

is rotating above the lost motion land

140

, the spring

120

provides an outwardly biasing force against the lever lower portion

136

, to normally bias the lever in the dashed line position shown in

FIGS. 4 and 6

. It is apparent that other methods may be used to engage the cam gear

98

with cam

100

. For instance, rather than the carriage actuated lever

130

, a servo mechanism could be used to engage gear teeth

105

,

142

with the transfer gear

96

. For that matter, other mechanisms could be used to provide incremental rotation to the cam

100

.

As shown in

FIGS. 3 and 5

, the dual sided adaptor cam

100

has an outboard surface

146

. A land

148

extends from the outboard surface

146

, with the land

148

having a periphery that defines a pick cam surface

150

. As shown in

FIGS. 2 and 4

, the cam

100

also has an inboard land surface

152

, which has a pick channel

154

and a pen-to-paper spacing (“PPS”) channel

156

formed therein. In operation, the pick pin

84

on pivot

80

travels through the pick channel

154

, whereas the PPS pin

86

travels through the PPS channel

156

during operation. Before discussing the operation of the adaptive media transport system

60

, one additional facet remains to be discussed.

Referring to

FIGS. 2 and 3

, pivoted to chassis

22

by a pair of pivot pins, such as pin

158

, is a plate lifter cam follower member

160

, which activates a plate lifter member

162

. The plate lifter member

162

extends along at least a portion of the underside of the pressure plate

62

. The plate lifter

162

has a pair of pins, such as pin

161

(FIG.

2

), which ride within slots, such as slot

163

formed within the lower surface of the pressure plate

62

. Pivoting action of the lifter

162

raises and lowers the rear edge of the lifter plate

62

. As mentioned earlier, the pressure plate

62

is biased upwardly by spring

65

(

FIG. 2

) into contact with the drive tires

74

-

76

. Lifting the pressure plate

62

upwardly brings the media into contact with the pick tire

78

and drive tires

74

-

76

, while lowering the pressure plate moves the media away from the tires

74

-

78

.

FIG. 4

shows an optional media guide

164

, located adjacent the rear edge of the pressure plate

62

. The media guide

164

is arcuate in nature to bend the media upwardly and around the exterior of the drive rollers

74

-

76

to assist in guiding print media around the periphery of the drive rollers. The media handling system may also include two or more pinch rollers, mounted on axles parallel to the drive axle

72

, and having outer surfaces which may be elastomeric in nature to grip a sheet of media between the pinch rollers and the drive rollers

74

-

76

For the purposes of illustration, two typical pinch rollers

165

,

166

are shown in their approximate locations in cross section in

FIGS. 7-14

. For clarity, the pinch rollers

165

,

166

have been omitted from the views of

FIGS. 2-6

.

In operation, the adaptive transport system

60

not only feeds media from the input tray

28

to the output tray drying wings

30

, but it also allows for adjustment of the pen-to-paper (PPS) spacing via a software routine which may be stored in the printer control

36

, the host computer, or some combination thereof. Merely for the purposes of illustration, this software routine is described herein as occurring within the printer controller

36

. First, the operation of the components of the transport system

60

will be described with respect to

FIGS. 7-14

, followed by a description of the software steps which control the action in

FIGS. 15-19

.

FIGS. 7-14

illustrate the interaction of the components of the adaptive media transport system

60

. The views in

FIGS. 7-14

show the outboard side

146

of the adaptor cam gear

100

.

FIGS. 7-14

show the interactions of the adaptor cam

100

with: (1) the pressure plate

62

, via the plate lifter cam follower

160

; and (2) the pivot

80

, via the interaction of the pick and PPS pins

84

,

86

with the pick and PPS cam tracks

154

,

156

, respectively. For clarity, the various drive gears

92

-

98

, the shift lever

130

, the chassis

22

, chassis wall

66

, and motor

88

are omitted from

FIGS. 7-14

.

FIG. 7

shows the initial position of the drive mechanism

90

. This position may be referred to as a rest or start position, and it is also the position from which media may be ejected or kicked from the drive mechanism to be totally supported by wings

30

, prior to being dropped into the output tray

32

. To begin the media pick cycle, the drive system begins a transition, shown in

FIG. 8

, as motor

88

and the drive mechanism

90

rotates cam

100

counterclockwise in the views, as shown by arrow

168

. Before beginning the pick cycle, at rest in

FIG. 7

the pick pin

84

is approximately midway along the pick track

154

, resting in a slightly dipped portion

170

of the track. The PPS pin

86

is located in a central open region

172

of the PPS track

156

. In these positions, the pins

84

,

86

have drawn the pivot leading edge

82

downwardly, which assists in ejecting media from the drive mechanism. In

FIG. 7

, the pick pressure plate cam

150

is shown holding cam follower

160

and the lifter plate

62

in lowered positions, which leaves the spring

65

(

FIG. 2

) in a compressed state.

FIG. 8

shows the drive system in transition from rest (

FIG. 7

) to begin the media pick cycle as motor

88

and the drive gears

92

-

98

rotate the adaptor cam

100

counterclockwise, as shown by arrow

168

. In this transition stage, a raising nose portion

173

the pressure plate cam

150

is at the final position where it holds the plate lifter cam follower

160

in a lowered position. The PPS pin

86

is adjacent the wall of the PPS cam track

156

, while the pick pin

84

is transitioning through cam track

154

toward an exit end

174

, but the relative position of the pivot

80

has not yet changed from the rest position of FIG.

7

.

FIG. 9

shows the beginning of the media pick operation, where the pressure plate cam follower

160

is no longer held in a lowered position by the pressure plate cam

150

. This allows the pressure plate spring

65

to push the pressure plate

62

upwardly, into a maximum position where it is engaged with the drive rollers

74

-

76

. The pick pin

84

continues to travel through the pick track

154

toward the exit end

174

, but the PPS pin

86

has left track

156

. The PPS pin

86

is advantageously constructed to be shorter than the pick pin

84

, which allows the PPS pin

86

to actually travel over a recessed portion

175

of the land surface

152

, located between tracks

154

and

156

. As the pressure plate

62

raises, the upper sheet of media resting thereon is drawn into the media feed path, preferably using the softer durometer pick tire

78

, assisted by the drive tires

74

,

76

, when rotated in the direction indicated by arrow

176

.

FIG. 10

shows a further continuation of the pick operation, where the pressure plate cam follower

160

is no longer held in a lowered position by the cam surface

150

. Indeed, while the cam surface

150

may be configured for continuous contact with follower

160

, the preferred design allows for different media thicknesses to be accommodated by the degree of compression of the pressure plate spring

65

. That is, the spring may be allowed to compress to different degrees to accommodate different thicknesses of media, such that the upward travel is not limited by the contact of the cam follower

160

with cam

150

. During this continuing of the pick operation, the PPS pin

86

is now back in contact with the PPS track

156

after traversing the recessed land

175

, while the pick pin

84

is now closer to the exit

174

of track

154

.

Upon completion of a successful pick routine,

FIG. 11

shows the beginning of a transition, where the pressure plate

62

is lowered. In

FIG. 11

, the further rotation of cam

100

in the direction of arrow

168

causes a lowering nose portion

178

of the cam

150

to force the follower

160

down. Downward motion of follower

160

allows the plate lifter member

162

to pull the pressure plate

62

downward into a print position. The pivot

80

has now been raised to a more upright, near-print position in FIG.

11

. The pick pin

84

has now exited the pick track

150

, and the PPS pin

84

has begun to enter a PPS adjust portion

180

of track

156

. In transitioning from

FIG. 11

to

FIG. 12

, it can be seen that the pressure plate

62

is lowered, which compresses spring

65

as the pressure plate cam

150

holds the follower

160

in a lowered position.

FIG. 12

shows the end of the media pick routine, and the beginning position of the PPS adjust routine. Briefly referring back to

FIG. 5

, it can be seen that the cam drive gear grooves

116

, which receive the splines

110

of cam

100

, are in a position of approximate engagement when located as shown in

FIGS. 5 and 12

. As noted before, in this region of travel, the cam spring

120

pushes the cam gear

98

toward the outboard side of the chassis

22

, and away from cam

100

. This action allows the teeth of the transfer gear

96

to ride within the lost motion region

140

of the cam gear teeth

105

. In this manner, the cam

100

is disengaged from being driven while the motor

80

continues to turn the drive tires

74

-

76

and incrementally advance media through the printzone

25

. Thus, the pivot

80

is decoupled from the media drive function so the pivot leading edge

82

is held in a position to accurately support media at a desired pen-to-paper spacing away from the printheads

54

,

56

during printing.

FIGS. 12 and 13

illustrate the PPS adjustment routine, with

FIG. 12

showing the beginning of the routine, where the pen-to-paper spacing is at a minimum, while

FIG. 13

shows the maximum PPS adjust position. To engage the cam gear

98

with the cam

100

during the PPS adjust routine, the printhead carriage

40

travels to the far left of the printer

20

, to engage the shift lever

130

(see FIG.

6

). The lower portion of the shift lever

130

forces the PPS adjust teeth

142

of cam gear

98

into engagement with the transfer gear

96

. The drive motor

88

then rotates a selected number of steps to advance the cam gear to position corresponding to a selected PPS spacing, either at the minimum position of

FIG. 12

, the maximum position of

FIG. 13

, or any other location therebetween in track

180

.

In rotating from the minimum position of

FIG. 12

, through the PPS adjustment portion

180

of track

156

, the cam

100

rotates through a total angle θ, shown in FIG.

12

. In rotating from the minimum to the maximum position, the pivot leading edge

82

can be seen to have been lowered, by a distance of ΔZ shown in

FIG. 13

, where the minimum PPS adjust position of the pivot from

FIG. 12

is shown in dashed lines. Upon reaching the desired location for the PPS pin

86

within the PPS adjustment track

180

, the printhead carriage

40

then moves away from the shift lever

130

. Without pressure from the lever

130

, the spring

120

pushes cam gear

98

toward the outboard side of the printer

20

, so teeth

142

are no longer engaged with the teeth of the transfer gear

96

, and instead, rotate within the cam gear lost motion portion

140

. Thus, at the proper PPS adjustment, with the adaptor cam

100

decoupled from motor

88

, the pivot

80

is held at a fixed elevation, and printing may commence. It is apparent that during operation, if the type of media should change or some adjustment in print quality be desired, that the carriage

40

can engage the shift lever

130

, and the PPS spacing may be adjusted by further cam rotation, either counterclockwise or clockwise, to locate pin

86

in a different portion of the PPS adjust track

180

. The usefulness of the PPS adjustment capability is discussed further below, with respect to the software system illustrated in

FIGS. 15-19

.

Upon completion of printing,

FIG. 14

shows a transition from the PPS adjust and print position (

FIGS. 12 and 13

) to the start position shown in FIG.

7

. During this

FIG. 14

transition, the pick pin

84

enters an entrance portion

182

of the pick track

154

. The PPS pin

86

now enters the free region

172

of the PPS track

156

. In making this transition, the pivot leading edge

82

begins to lower, to the rest position shown in FIG.

7

. During this transition, the pressure plate

62

is held in a lowered position by engagement of cam follower

160

with the pressure plate cam

150

.

To initiate the transition of

FIG. 14

, the printhead carriage

140

engages the shift lever

130

, compressing spring

120

(FIG.

6

), which engages the narrow cam gear teeth

142

with the transfer gear

96

. Rotation of the cam gear past the band of narrow teeth

142

allows the full width of the cam gear teeth

105

to engage the transfer gear

96

. The frictional forces of this full tooth width engagement overcomes the axial force of spring

120

, so the gears

96

and

98

remain engaged even when the shift lever pressure is removed. Thus, when rotated past the lost motion region

140

and teeth

142

, the carriage

40

is free to return the pens

50

,

52

to the service station for servicing. Continued rotation of cam

100

discharges the printed media onto the drying wings

30

, and brings the drive mechanism back to the rest position of FIG.

7

. When at rest, the cam gear

98

is held in a fixed position through engagement with the transfer gear

96

. As the pivot

80

pivots downwardly to the rest position of

FIG. 7

, the output tray wings

30

advantageously raise upwardly into a retracted position for storage, as shown by arrows

184

in FIG.

1

. The operation of the wings

30

may occur in conjunction with, or independently from, the operation of the adaptive media transport system

60

illustrated herein.

Method of Operation

FIGS. 15-19

are flow charts showing the various steps of engagement illustrated in

FIGS. 7-14

. To accommodate for manufacturing tolerance accumulations of the various parts used to construct the media transport system

60

, the initial adjustment of the PPS spacing may occur at the factory, as illustrated in the factory PPS tolerance adjust flow chart

200

in FIG.

15

. For instance, for a particular printer assume that the optimal adjust is determined to occur at an angle of 10° for θ (FIG.

12

). This 10° rotation value may be easily translated in to a particular number of steps which motor

88

turns. This particular step value corresponding to θ=10° then may be permanently stored in a read only memory (ROM) portion of the printer controller

36

and recalled for a nominal adjustment prior to printing.

The process of

FIG. 15

starts at an operator initiated step

202

, which generates a start command

202

. In response to the start command, the actual pen-to-paper spacing is measured in a measure manufactured PPS step

206

using gauges or optical means, for example, and a signal

208

corresponding to measured manufactured PPS is supplied to a comparator portion

210

. The comparator

210

compares the magnitude of the measured manufactured PPS signal

208

with a nominal PPS value, and if they match, emits a YES signal

212

. The YES signal

212

indicates a perfect nominally toleranced system

60

requiring zero factory adjustment. This YES signal

212

is sent to a factory PPS tolerance storage routine

214

where the PPS tolerance adjust steps are stored in memory, such as in a ROM (read only memory) portion of the printer controller

36

. The YES signal

212

corresponds to a PPS tolerance adjust steps of zero, since the printer is at the nominal design PPS spacing. Following the storage step

214

, a completion signal

216

is emitted and an end factory PPS tolerance adjust step

218

is performed, perhaps by giving an assembly worker a visual signal, or by automatically allowing the printer to proceed down the assembly line.

A more likely scenario is that the comparator

210

finds that the magnitude of the measured manufactured PPS signal

208

does not match a nominal PPS value, so a NO signal

220

is transmitted to step

222

. In step

222

, the PPS difference between the measured PPS and nominal PPS values is determined, and a difference signal

224

is supplied to a look-up routine

226

. The routine

226

looks-up the number of motor steps encoder counts, or encoder positions required to adjust for the PPS difference, then emits a signal

228

to a move carriage step

230

. The look-up routine

226

also stores this retrieved value for later recall until a new printer is tested.

Having determined the number of motor steps required to adjust the PPS pin

86

to a location in the adjustment portion

180

of track

156

, the system will now verify that this adjustment will indeed bring the PPS spacing ΔZ (

FIG. 13

) to the nominal value. In response to signal

228

, in step

230

the printer controller

36

moves the carriage

40

in a conventional manner to engage the shift lever

130

, which couples the adaptor cam

100

to motor

88

. When the controller

36

receives conventional positional feed back that the carriage has engaged lever

130

, the controller then issues a drive motor signal

232

. The extent to which motor

88

rotates is controlled by step

234

to be the number of steps looked-up in step

226

to locate the pivot leading edge

82

at what is thought to be the nominal PPS spacing. At the conclusion of this repositioning, a signal

236

is supplied to another measurement step

238

, where the adjusted PPS is measured, and a measured adjusted PPS signal

240

is generated.

Once again, the magnitude of the adjusted PPS signal

240

is compared to the nominal PPS value by a second comparator

242

. If the adjustment was unsuccessful, a NO signal

244

is supplied back to the determine difference step

222

. The steps

222

through

242

may be repeated as necessary until the adjustment to the nominal PPS is successful and a YES signal

246

is generated. During any successive iterations of steps

222

through

242

, the values retrieved in step

226

are all stored. In response to receiving the YES signal

246

, step

248

sums together the values stored at step

226

to arrive at a total number of PPS tolerance adjust steps, represented by signal

250

. The summation of these tolerance adjust steps is stored in a memory portion of the controller

36

in step

214

as described above, and the factory adjust routine terminates at step

218

.

It is apparent that the majority of the factory adjust process

200

may be automated at the factory, rather that requiring extensive operator involvement, manual adjustments, tightening of set screws to hold the adjustment, etc. This is especially true if the measurement device is some type of transducer, such as an optic device that generates the measurement signals

208

and

240

and provides them as input signals to the printer controller

36

. In this manner, a smart self-testing printer

20

is provided. Alternatively, the process in flow chart

200

may be performed in part by an auxiliary computer or other processor communicating with the printer controller

36

. This system may also be advantageously used by personnel servicing a printer. In either implementation, human error is virtually eliminated from the process. The tolerance adjust value is stored in ROM in the printer controller, where it is accessed prior to each printing job (described further below). Thus, the printer cannot be jostled out of a mechanical adjustment during shipping.

Moving from the manufacturing context, flow chart

300

in

FIGS. 16-19

shows a printing operation having several routines comprising several steps each, such as the pick routine

302

in FIG.

16

. The pick begins with step

304

, where the controller

36

issues a start pick signal

306

indicating that a sheet is to be printed. In response to the start pick signal

306

, from the rest position of

FIG. 7

, in step

308

the motor

88

rotates the adaptor cam

100

to raise the lifter plate

62

to touch the drive and pick rollers

74

-

78

, as shown in transitioning through

FIG. 8

to the

FIG. 9

position. Upon accomplishing step

308

, the controller

36

generates a continue rotation signal

310

which continues rotation of the drive and pick rollers

74

-

48

to pick media from the input tray

28

in step

312

, while simultaneously raising the media support pivot

80

in step

314

. The operation of steps

312

and

314

is shown by the transition of the drive mechanism

90

from FIG.

9

through

FIGS. 10 and 11

, after which signal

316

is then generated.

Upon receiving signal

316

, rotation of the adaptor cam

100

continues in step

318

to lower the lifter plate

62

to the end feed position of FIG.

12

. Upon reaching the

FIG. 12

position, signal

320

is generated by controller

36

and rotation of the cam

100

is stopped. In this position, the transfer gear

96

engages only the narrow teeth

142

, and spring

120

pushes the cam gear

98

out of engagement with the transfer gear, uncoupling the cam

100

form the motor

88

in step

322

. At this point signal

324

is generated to indicate that the pick routine

302

has concluded at step

326

, and an end pick signal

328

is generated.

In

FIG. 17

, a PPS adjust routine

330

of the process

300

is shown receiving the end pick signal

328

. In response to signal

328

, a begin PPS adjust routine step

332

generates a start signal

334

, which is received by a determine media thickness step

336

. The determine thickness step

336

also receives another input signal

338

, which may be generated by one or a combination of a host computer

340

, an operator activated input mechanism

342

, and a sensor input

344

. The input signal

338

carries information as to what the media thickness may be. The manner in which the printer controller

36

determines that an envelope is being feed to the printer rather than plain paper or other media, may be accomplished in a variety of ways. For example, it could be input by the user from a keypad on the printer exterior, or through user input from the host computer

340

. The host computer

340

may automatically generate signal

338

based upon the type of document being printed, without further user input. Alternatively, a media thickness sensor

344

could be installed adjacent to chassis wall

68

, for example, to sense the thickness of an upcoming sheet of media.

Once step

336

determines the media thickness, signal

346

is supplied to a look-up step

348

. Step

348

correlates the media thickness from the information in signal

346

with the number of motor steps required to for an ideal PPS media adjustment, and generates a media adjust signal

350

. Upon receiving the media adjust signal

350

, or simultaneously with the looking-up in step

348

, step

352

looks-up the motor steps for PPS tolerance adjust stored at the factory in the controller memory in step

214

of

FIG. 15. A

PPS tolerance adjust signal

354

is supplied to a totaling step

356

, and the media adjust signal

350

is also delivered to the step

356

, shown here as passing through block

352

. In step

356

, a total PPS adjust signal

358

is generated by sum the number of motor steps required for the PPS media adjust from step

348

and the PPS tolerance adjust from step

214

(FIG.

15

). For instance, an envelope or other thick media may, for instance, take an additional 10° of rotation for angle θ to increase the ΔZ PPS spacing. When the controller

36

is made aware that an envelope is being printed, the controller can direct motor

88

to step not only the initial 10° required to accommodate the particular printer tolerances, but an additional 10° to increase the PPS spacing to accommodate the envelope.

Upon determining the number of motor steps required to adjust the PPS, in step

360

the controller then moves the carriage

40

to engage shift lever

130

to couple the adaptor cam

100

to motor

88

, as described above with respect to step

230

of

FIG. 15

, and upon completion signal

362

is generated. In response to receiving signal

362

, step

364

drives the motor

88

for number of steps for total PPS adjust of signal

358

to move the pivot

80

to the selected PPS print position, somewhere at or between the minimum position of FIG.

12

and the maximum position of FIG.

13

. When in the selected PPS print position, a signal

366

is generated to indicate that step

368

may now let the controller

36

move the carriage

40

away from the shift lever

130

to uncouple the adaptor cam

100

from motor

88

, as described for step

332

of FIG.

16

. Upon completion of step

368

, a signal

370

is supplied to an end PPS adjust routine step

372

which then generates an end PPS adjust routine signal

374

.

In

FIG. 18

, a print routine

380

of the process

300

is shown receiving the end PPS adjust routine signal

374

. In response to signal

374

, a begin printing routine step

382

generates a start signal

384

, which is received by a uniform media thickness query step

386

. The uniform media thickness query step

386

looks for changes in the media thickness or effective thickness due to ink saturation causing cockle (described in the Background portion above), and when found, supplies a NO signal

338

to the determine thickness step

336

of

FIG. 17

where further adjustments are made by the PPS adjust routine

330

.

Thus, the PPS adjustment may be made during printing to accommodate different media thicknesses. Note, this PPS adjust not only need occur at the beginning of printing a sheet, but may also occur during the printing of the sheet. For example, a new type of paper has recently become available upon which to print banners, for instance, one that would say “Happy Birthday” and would be displayed on a wall. This banner paper is supplied in Z-fold stack, for instance of letter sized paper, joined by perforated portions along the top and bottom edges. The earlier printers were vulnerable to damage when using banner-type paper. Since the perforations usually have paper fibers extending therefrom, there is the increased damage that paper fibers could be jammed into the nozzles, causing permanent damage. Moreover, even if the nozzles are not damaged, contact of the perforations with the nozzle plate could smear ink on the pen face, dirtying the printhead and damaging the image in the region of the perforation. This adaptive system

60

of printing on perforated paper avoids the risk of the upwardly projecting tents at a perforation hitting the orifice plates of printheads

54

,

56

during printing.

When feeding through the printer

20

, the major portion of the perforated paper is the thickness of plain paper. However, as the perforation approaches the print zone there is an increase in the apparent thickness of the media, due to the perforation raising up toward the printheads

54

,

56

. Thus, as a perforation is approached (the approach of which may be determined by counting the number of steps motor

88

has advanced since printing of the banner began) carriage

40

could engage lever

30

and cam

100

could be advanced to increase the PPS spacing ΔZ in the region of the perforation. Then following printing at the perforation, the PPS spacing could be readjusted back to the nominal position as the carriage again engages lever

130

.

Besides adjusting the pen-to-paper spacing for the type of media, the controller

36

may also adjust the pen-to-paper spacing based on the type of image being printed. For example, an image having a large amount of ink, such as a photographic type image or graphics, may saturate the media during printing, causing the media fibers to expand, causing media cockle. Thus, for these heavily saturated images, the controller

36

may interpret the incoming data stream from the host computer as being a saturated image, and increase the pen-to-paper spacing as described above with respect to

FIGS. 12 and 13

. Also from the host computer

340

, the user may make a selection that a postcard, rather than an envelope, is being printed. In this case, the pen-to-paper spacing may be adjusted for a postcard thickness, rather than an envelope thickness, allowing the postcards to be printed at a much closer pen-to-paper spacing gap, resulting in a higher quality image on the postcard. A smaller pen-to-paper spacing is believed to increase print quality, because there is less distance for the ink droplets to travel, and a lesser chance of over-spray occurring which would blur the image. Indeed, in a humid environment, it may be desirable to increase the pen-to-paper spacing to account for humidity absorbed by normal media, which may cause it to thicken somewhat, requiring a larger gap.

Returning to

FIG. 18

, when the media thickness is uniform, step

386

generates a YES signal

390

, which is transmitted to a hold pivot position step

392

until printing of the sheet is complete, indicated by signal

394

. Upon receiving the printing complete signal

394

, a finish printing routine step

396

concludes the routine

380

by issuing a finished printing signal

398

. After printing is complete, a discharge media routine

400

portion of the overall process

300

initiates media discharge from the media transport system

60

. In response to the finished printing signal

398

, a begin media discharge step

402

generates a start signal

404

, which in turn causes the carriage

40

to engage the shift lever

130

to couple the adaptor cam

100

to motor

88

in step

406

, in the same manner as described above for the steps

230

and

360

. After sufficient movement has occurred to mesh the full width of the cam gear teeth

105

with the transfer gear

96

, indicated by signal

408

, the carriage

40

may be returned to the service station

45

in step

409

.

Upon completion of step

406

and step

409

, if this optional step is performed, a signal

410

indicates that rotation of the drive tires

74

-

76

may continue in step

412

, and that cam

100

should continue to rotate to lower the pivot

80

to the rest position in step

414

. The illustrated simultaneous occurrence of step

412

and

414

is shown by the transition of the drive mechanism

90

from the printing position of

FIGS. 12 and 13

. through the view of

FIG. 14

, and to conclude with the mechanism

90

in the rest position of

FIG. 7

, at which point signal

416

is generated. As shown in

FIG. 19

, in response to signal

416

, an end media discharge step

418

issues a media discharge complete signal

420

.

After printing and discharging the printed sheet, it may be helpful to determine whether there are additional sheets to be printed. In

FIG. 19

, in response to signal

420

this question is asked in an end print job query step

422

. If additional sheets remain to be printed, a NO signal

424

is issued to a return to the begin pick routine step

426

, which starts again at step

304

of FIG.

16

. If the print job is complete, then step

422

issues a YES signal

428

to a finish print job step

430

, in response to which the printer

20

remains at idle, awaiting the next print job.

It is apparent that the factory tolerance adjust routine

200

and the printing routine

300

are discussed herein by way of example only, and may be varied in their individual steps or sequencing an still fall within the scope of the claims below. For example, in

FIG. 18

, when transitioning between the end of the print routine

380

and the beginning of the discharge routine

400

, steps

396

and

402

may be combined or totally omitted. Indeed, the speed of data processing and printing would likely be improved and thus preferred if the information freely flowed from one portion of the process to the next with minimal impediments. The use of the begin routine and finish routine steps, among others, in the flow chart is primarily for clarity in helping the reader better understand the entire process by breaking it down into smaller segments. Such streamlining modifications to the illustrated information flow process are apparent to those skilled in the art, and clearly fall within the scope of the claims below. Thus, practice of the claimed invention is not limited to the embodiments illustrated herein.

Conclusion

For simplicity, and minimization of parts, the illustrated embodiment of the adaptive transport system

60

is preferred. Moreover, the fewer number of parts used in transport system

60

, here, approximately seven moving gear parts as opposed to seventeen parts in the earlier designs, necessarily provides a quieter operating mechanism due to less interaction of gears and components. Furthermore, the lesser number of components in system

60

renders this system more economical to produce, as a fewer number of parts need to be procured, and then less labor time is required to assembled the parts. Moreover, the PPS adjust routine advantageously provides for automatable factory or service calibration of the PPS adjustment without requiring clumsy access panels, and which remains secure during shipping.

It is apparent that while the illustrated embodiment has been shown with respect to a replaceable inkjet cartridge, the principles of the adaptive transport system

60

may be applied to what is known in the art as an “off-axis” ink delivery system, where the main ink reservoir is stored at a stationary location for delivery to the reciprocating printhead, via flexible conduits or tubing, for instance. It is also apparent that the principles of the adaptive transport system

60

may be applied to what is known in the art as a “page-wide” printhead array, where the printhead extends over the entire width of the page, so reciprocation is unnecessary. In such a page-wide array printing mechanism, the clutch mechanism may be operated by a small solenoid, or through cooperation with one of the service station components.

Advantageously, operation of the adaptive transport system

60

allows for automatic adjustment of pen-to-paper spacing in response to the type and thickness of media being used to provide the best print quality. As a further advantage, the pen-to-paper spacing may also be adapted in response to the type of image being printed. For text or other minimal fill images, the spacing may be close to provide a crisper, cleaner image. For heavily filled images, such as charts, graphics or photographic images, that saturate the media with ink, the spacing may be increased to accommodate paper cockle, avoiding collision between the media and the printhead.

Number	Name	Date	Kind
4843338	Rasmussen et al.	Jun 1989	A
4872026	Rasmussen et al.	Oct 1989	A
4927277	Niikawa	May 1990	A
5000594	Beehler et al.	Mar 1991	A
5135321	Olsen et al.	Aug 1992	A
5192141	Chung et al.	Mar 1993	A
5261038	Adreher et al.	Nov 1993	A
5316285	Olson et al.	May 1994	A
5326090	Hock et al.	Jul 1994	A
5414453	Rhoads et al.	May 1995	A
5466079	Quintana	Nov 1995	A
5468076	Hirano et al.	Nov 1995	A
5510815	Linder et al.	Apr 1996	A
5559538	Nguyen et al.	Sep 1996	A
5570959	Moriwaki et al.	Nov 1996	A
5581289	Firl et al.	Dec 1996	A
5624196	Jackson et al.	Apr 1997	A
6102509	Olson	Aug 2000	A

	Number	Date	Country
Parent	08/652720	May 1996	US
Child	09/604187		US

Adaptive method for handling inkjet printing media

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Disclaimer

Abstract

Description

Claims

Parent Case Info

US Referenced Citations (18)

Continuations (1)