EP0775586A1

EP0775586A1 - Inkjet print carriage width minimization

Info

Publication number: EP0775586A1
Application number: EP96302190A
Authority: EP
Inventors: David E. Hackleman
Original assignee: Hewlett Packard Co
Current assignee: HP Inc
Priority date: 1995-11-21
Filing date: 1996-03-28
Publication date: 1997-05-28
Also published as: JPH09174826A

Abstract

Print carriage path length is minimized for a multiple-pen print carriage (72) shuttling pens (62-68/92-98) of differing resolution. In one embodiment, the carriage holds a 600 dpi black ink pen (62, 94) and three 300 dpi colored ink pens (64-68/92,96,98). The printhead for each lower resolution pen has nozzles aligned in a single row (76), while the printhead for the higher resolution pen has nozzles aligned in multiple (e.g., two) rows (72,74). Alternatively the printhead for the lower resolution pens (100) have active nozzles aligned in one active row (102 or 104). The pens are aligned side-by-side within the shuttle carriage. The higher resolution pen takes an inner position within the shuttle carriage. By positioning the lower-resolution pen nozzles in a single row and positioning the higher resolution pen in an inner position, the carriage width of the printer is shortened by several millimeters.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to inkjet printer construction, and more particularly to inkjet pen, print element and carriage assembly construction for inkjet printers having multiple pens.
Computer and printer manufacturers targeting the portable computer user strive to reduce the size and weight of their products. One objective of manufacturers is to construct a printer device, for example, that fits inside a conventional briefcase. This objective results in a design limitation that a printer be 300 millimeters or less in length. Such objective has been met for black inkjet printers, but is a more difficult task for color inkjet printers.
A conventional black inkjet printer include an inkjet pen which scans which across a media sheet. The pen is held in a shuttle carriage which moves along a rail. As the pen is carried in the shuttle carriage, the inkjet nozzles at the pen's printhead emit ink onto the media sheet. Typical resolutions are 300 dots per inch and more recently 600 dots per inch ("dpi").
For a colored inkjet printer multiple pens are used. Typically, each pen prints ink of a different color. For example one pen prints black ink, while 3 additional pens print cyan, magenta and yellow inks, respectively. The multiple pens are located side by side in an enlarged shuttle carriage. As with the black inkjet printer embodiment, the multiple pen carriage moves along a rail to scan the media sheet to receive ink. With the four pens positioned side by side, the shuttle carriage holding multiple pens is wider than the shuttle carriage for the black inkjet printer. Also, the shuttle carriage path spans a longer distance due to its relatively longer width, (e.g., by approximately 3 inkjet pen widths). Such increased carriage path distance makes it difficult to achieve a portable colored inkjet printer that can fit within a briefcase, (e.g., that is less than 300 mm.). Accordingly, there is a need for minimizing printer width of a colored inkjet printer to make the printer more "portable".

SUMMARY OF THE INVENTION

According to the invention, print carriage path length is minimized for a multiple-pen print carriage shuttling pens printing at differing resolution. In one embodiment, the carriage holds a 600 dpi black ink pen and three 300 dpi colored ink pens. In one embodiment the printheads for each pen are the same, but only a subset of nozzles are active for printing at lower resolution.
According to one aspect of the invention, the printhead for each lower resolution pen has active nozzles aligned in a single row, while the printhead for the higher resolution pen has active nozzles aligned in multiple (e.g., two) rows. The single row of active nozzles for the lower resolution pens are either centered or offset toward one edge.
According to another aspect of the invention, the higher resolution pen takes an inner position within the shuttle carriage. The pens are aligned side-by-side within the shuttle carriage. By selecting the active lower-resolution pen nozzles to be in a single row and by positioning the higher resolution pen in an inner position, the carriage width of the printer is shortened by several millimeters.
These aspects are embodied in an inkjet print carriage, including multiple inkjet pens, a shuttle carriage and a rail. The pens are carried in the shuttle carriage along the rail to print onto a media sheet while scanning the sheet. The multiple pens including a first set of pens (e.g., colored pens) printing at one resolution and at least one other pen (e.g., black pen) printing at a higher resolution. Each one of the first set of pens has a first printhead of inkjet nozzles. In one embodiment the nozzles are arranged in a single row. The row is centered across the width of the printhead and runs lengthwise along the first printhead. Alternatively, the row is off-center toward an edge. The higher resolution printhead(s) include multiple rows. The printheads of all pens are arranged side by side in the shuttle carriage. In one embodiment all the printheads are permanent printheads. Permanent printheads as used herein means printheads that are not replaced each time ink runs lows, but which instead last the life of the printer or are replaced less often than ink re-filling.
The outer printheads among the arrangement of side by side printheads are first printheads having a single row of active nozzles. The higher resolution printhead(s) with the multiple rows of active nozzles occupy intermediary positions relative to the outer printheads. Inkjet carriage path is minimized by having a single row of active nozzles.
One advantage of the shorter carriage width is that a printer spanning a length less than, equal to or approaching 300 mm is achieved for various embodiments. These and other aspects and advantages of the invention will be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram of a conventional print carriage assembly;
Fig. 2 is a diagram of a conventional nozzle layout for a higher resolution black pen and lower resolution colored pens;
Fig. 3 is a diagram of a potential alternative nozzle layout for a higher resolution black pen and lower resolution colored pens;
Fig. 4 is a diagram of an alternative nozzle layout according to an embodiment of this invention;
Fig. 5 is a diagram of an alternative nozzle layout according to another embodiment of this invention;
Fig. 6 is a block diagram illustrating minimum printer carriage width for the conventional nozzle layout of Fig. 2;
Fig. 7 is a block diagram illustrating minimum printer carriage width for the nozzle layout of Fig. 3; and
Fig. 8 is a block diagram illustrating minimum printer carriage width for the nozzle layout of Fig. 4; and
Fig. 9 is a block diagram illustrating minimum printer carriage width for the nozzle layout of Fig. 5.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Print Carriage Assembly

Fig. 1 shows a conventional inkjet print carriage assembly 10. In various implementations the print carriage assembly 10 is part of an inkjet printer, fax machine, or copy machine. The assembly 10 includes four inkjet pens 12, 14, 16, 18. Pen 12 prints black ink K, while pens 14, 16 and 18 print respective colored inks C1, C2, C3, (e.g., cyan, magenta and yellow). Each pen includes a printhead 20, 21 of inkjet nozzles. A shuttle carriage 22 carries the pens along a rail 30. The shuttle carriage 22 is driven along the rail 30 in response to a drive signal received from a carriage controller 32. As the shuttle carriage 22 scans across a media sheet, the respective printheads 20, 21 print markings onto the media sheet under the control a printhead controller 34.
Also shown is a drive roller 40 including multiple elastomeric "tires" 42 and a rotating shaft 44. The drive roller 40 is driven by a motor 46 based on commands from a media transport controller 48. The various controllers 32, 34, 48 are in communication with a print processor 50 and memory 52.
Fig. 2 shows the printheads 20, 21 of the pens 12-18 for a higher-resolution black pen 12 (e.g., 600 dpi) and three lower-resolution colored pens 14-18 (e.g., 300 dpi). The black pen 12 includes multiple rows 23, 24, 25, 26 of nozzles 27. The colored pens, 14, 16, 18 include two rows 28, 29 of nozzles 27. Conventionally, the black pen 12 is positioned at one end of the row of side-by-side pens 12-18.

Printhead Layouts

Fig. 3 shows an alternative printhead layout for alternative pens 62-68. The layout includes a higher resolution black pen 62 adjacent to multiple lower resolution colored pens 64, 66, 68. In one embodiment the black pen prints with 600 dpi resolution, while three colored pens (e.g., cyan, magenta and yellow) print with 300 dpi resolution. The black pen 62 includes a printhead 70. The printhead 70 includes multiple rows 72, 74 of nozzles 76. In a preferred embodiment there are two rows 72, 74 of nozzles 76. Also, the colored pens 64, 66, 68 include respective printheads 71. Each printhead 71 includes a single row 78 of nozzles 76.
The nozzle layout differs for the higher resolution pen 62 relative to the lower resolution pens 64, 66, 68. The higher resolution pen includes multiple rows 72, 74 running the length of printhead 70. In the preferred 2-row embodiment each row 72, 74 is offset from its closest elongated pen edge 80, 82 by a distance d₃. The lower resolution pens 64, 66, 68 each include a single row 78 running the length of the respective printheads. The single rows 78 are generally centered across the width of the printhead 71. Each nozzle 78 on printhead 71 has a distance d₄ from nozzle center to elongated pen edges 84, 86.
In comparison to the conventional printhead 20, printhead 70 is narrower having a width w₃ which is less than the printhead 20 width w₁. The outermost rows 23, 26 of conventional printhead 20 are offset by a distance, d₁, as measured from nozzle center to nearest elongated pen edge 31, 33. The printhead 70 has its outermost rows 72, 74 offset by a distance d₃, as measured from nozzle center to nearest elongated pen edge 80, 82. Distance d₃ is any of shorter, longer or equal to distance d₁.
In comparison to the conventional printhead 21, printhead 71 is narrower having a width, w₄ which is less than printhead 21 width, w₂. The rows 28, 29 of printhead 21 are each offset by a distance d₂, as measured from nozzle center to nearest elongated pen edge 35, 37. The printhead 71 single row 78 is centered having an offset d₄, as measured from nozzle center to each elongated pen edge 35, 37.
Fig. 4 shows a preferred arrangement of pens 62, 64, 66, 68 in which the higher resolution pen 62 has an inner position among the arrangement of pens 62-68. In various embodiments, the higher resolution pen(s) are located in intermediary positions, as distinguished from outer positions. Preferably the two outer positions in a row of pens including higher resolution and lower resolution pens are lower resolution pens. According to an alternative preferential arrangement, the two outer positions in a row of pens are occupied by pens having a single row of nozzles, regardless of resolution. Each nozzle in the single row being centered across the width of its printhead. According to an alternative embodiment the single rows are off-center, instead of being centered.
Fig. 5 shows an alternative preferred embodiment in which a four pens 92, 94, 96 and 98 are arranged side by side. Each pen 92-98 includes a printhead 100 having two or more sets of columns. Each set includes one or more columns of nozzles 27. According to an aspect of the invention, the outer pens 92 and 98 print at a lower resolution than at least one of the intermediary pens 94, 96. To do so, the outer pen 92 prints using the set 104. Set 102 is not used for lower resolution printing of pen 92. Also, the outer pen 98 prints using the set 102. Set 104 is not used for lower resolution printing of pen 98. The higher resolution pen (e.g., pen 94) prints using both sets 102, 104. The lower resolution pen (e.g., 96) prints using either one, but not both of sets 102 and 104.

Minimal Carriage Path Width

Figs. 6-9 show the minimum carriage path widths for the pen arrangements of Figs. 2-5, respectively. Fig. 6 shows the minimum carriage path width for pens 12-18 of Fig. 2. For a printer printing to a media sheet having maximum page width, w_p, the minimum carriage path width, P_a, is given below:
Typical values for the dimensions are given below:
w_p = 215.9 mm
w₁ = w₂ = 13 mm
d₁ = d₂ = 2.0 mm
Thus, P_a = 215.9 + 78 + 26 - 2 - 2 = 315.9 mm
Such minimum width is approximately 15 mm too long.
Fig. 7 shows the minimum carriage path width for pens 62-68 as arranged in Fig. 3. For a printer printing to a media sheet having maximum page width, w_p, the minimum carriage path width, P_b, is given below:
Exemplary values for the dimensions are given below:
w_p = 215.9 mm
w₃ = w₄= 12-13 mm
d₃ = 2.0 mm
d₄ = (12 mm to 13 mm )/2.0 = 6 mm to 6.5 mm
Thus, P_b = 215.9 + (60 to 75) + (24 to 26) + (6 to 6.5) - 2 = 303.9 to 311.4 mm Such minimum width is approximately 4-12 mm too long.
Fig. 8 shows the minimum carriage path width for pens 62-68 as arranged in Fig. 4. For a printer printing to a media sheet having maximum page width, w_p, the minimum carriage path width, P_c, is given below:
Exemplary values for the dimensions are given below:
w_p = 215.9 mm
w₃ = w₄ = 12-13 mm
d₃ = 2.0 mm
d₄ = (12 mm to 13 mm )/2.0 = 6 mm - 6.5 mm
Thus, P_c = 215.9 + (48 to 52) + (24 to 26) + (12 to 13 ) = 299.9 to 306.9 mm This preferred Fig. 4 arrangement gives a minimum carriage path distance which is 4 to 5.5 mm better than the Fig. 3 arrangement and 9 to 16 mm better than the Fig. 2 arrangement of the conventional printheads 20, 21. By positioning the higher-resolution pen in an inner position the minimum carriage path is reduced by 4.5 mm. The remaining reduction is due to achieving narrower pens.
Even for the situation in which conventional thickness 13.0 mm pens are used for the Fig. 4 arrangement and printhead layouts, the desired 300 mm minimum distance is met by reducing the page width w_p by 6.9 mm. More specifically, minimum left and right margins of approximately 3.5 mm are imposed. This is an acceptable margin limitation which is similar to the minimum margins of conventional laser printers.
Fig. 9 shows the minimum carriage path width for pens 92-98 as arranged in Fig. 5. For a printer printing to a media sheet having maximum page width, w_p, the minimum carriage path width, P_c, is given below:
Exemplary values for the dimensions are given below:
w_p = 215.9 mm
w₅ = w₆ = 12-13 mm
d₆ = d₇ = 2.0 mm
Thus, P_c = 215.9 + (48 to 52) + (24 to 26) + 2 + 2 = 291.9 to 297.9 mm
Note that this minimum carriage width of 291.9 to 297.9 mm also applies for a configuration of pens 62-68 in which the rows are off center to correspond to the position of the active rows (e.g., sets) 102, 104 among pens 92, 96 and 98 of Figs. 5 and 9. Accordingly, the desired 300 mm minimum distance is met by the configuration of Fig. 9.
In summary print carriage path is minimized by positioning the higher resolution pen(s) in intermediary positions. Print carriage path is further reduced by (i) narrowing pen width to approximately 12 mm or less, (ii) incurring print margin minimums (e.g., totaling approximately 6.9 mm for the combined left and right margins), (iii) using only a set of nozzles for low resolution printing and strategically selecting which set (e.g., left set or right set) to use, or (iv) for a single row of nozzles printing at lower resolution, positioning the nozzles off center to one side for one outer pen and off-center toward the opposite side for the other outer pen.

Meritorious and Advantageous Effects

One advantage of the invention is that smaller lightweight portable color-ink devices are achieved. Another advantage is that portable color-ink devices of smaller length can be achieved which fit within a conventionally-sized briefcase.
The advantages of the invention are even more apparent for inkjet pens having permanent printheads, (i.e., printheads that are not replaced each time ink runs low, but which instead last the life of the printer or are replaced periodically, but less often than ink re-filling.) For such printheads, the relative positioning of the pens is accurate to fine tolerance levels. This allows designers to avoid accounting for spacing between pens and play in the pen positioning when determining minimum carriage path length.
Although a preferred embodiment of the invention has been illustrated and described, various alternatives, modifications and equivalents may be used. Therefore, the foregoing description should not be taken as limiting the scope of the inventions which are defined by the appended claims.

Claims

An inkjet print carriage, comprising:
a first plurality of first inkjet printheads (71/100) printing at a first resolution;

a second inkjet printhead (70/100) printing at a second resolution, the second resolution greater than the first resolution;

a rail (30) extending across a print media path width;

a shuttle carriage (72) for moving along the rail;

wherein the second printhead and the first plurality of first printheads are arranged side by side at the shuttle carriage and move with the shuttle carriage;

wherein outer printheads among the printheads arranged side by side are first printheads and wherein the second printhead occupies an intermediary position relative to the outer printheads; and

wherein printing onto a media sheet is achieved by scanning the printheads along the rail via the shuttle carriage.
The inkjet print carriage of claim 1, in which inkjet carriage path is minimized by outer printheads each having a single row of nozzles (76) centered across printhead width.
The inkjet print carriage of claim 1, in which each one of the outer printheads have a first edge (106) and a second edge (108), a first one of the outer printheads having the first edge adjacent to another printhead and the second edge away from the other printheads, a second one of the outer printheads having the second edge adjacent to another printhead and the first edge away from the other printheads, and wherein inkjet carriage path is minimized by said first one of the outer printheads having all active nozzles located toward its first edge and said second one of the outer printheads having all active nozzles located toward its second edge.
The inkjet print carriage of claim 3, in which each one of the outer printheads comprise a single row of nozzles (76).
The inkjet carriage of claim 3, in which each one of the outer printheads comprise a plurality of rows of nozzles, said plurality of rows grouped into two sets of nozzles, a first set (102) located toward the first edge, a second set (104) located to the second edge, and in which only one of the two sets is active for a given outer printhead for printing at the first resolution.
The inkjet print carriage of claim 1, in which each one of the first plurality of first printheads and the second printhead are permanent printheads.
A method of minimizing inkjet carriage path length of an inkjet shuttle carriage (72) carrying a first plurality of first inkjet printheads (71/100) and a second inkjet printhead (70/100), each one of the first plurality of printheads printing at a first resolution, the second printhead printing at a second resolution, the second resolution greater than the first resolution, the method comprising the steps of:
arranging the first plurality of first printheads and the second -printhead side by side with outer printheads being first printheads and the second printhead being in an intermediary position relative to the outer printheads, wherein each one of the outer printheads has a first edge (106) and a second edge (108), a first one of the outer printheads having the first edge adjacent to another printhead and the second edge away from the other printheads, a second one of the outer printheads having the second edge adjacent to another printhead and the first edge away from the other printheads;

selecting all active nozzles of said first one of the outer printheads as being located toward the first one's first edge; and

selecting all active nozzles of said second one of the outer printheads as being located toward the second one's second edge.
The method of claim 7, in which each one of the outer printheads comprise a single row (78) of nozzles.
The method of claim 7, in which each one of the outer printheads comprise a plurality of rows of nozzles, each said plurality of rows grouped into two sets of nozzles, a first set (102) located toward the first edge, a second set (104) located toward the second edge, and in which only one of the two sets is active for printing at the first resolution.