JP2004224042A - Ink jet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording device which facilitates printing positioning by adjusting printing timing of each head unit. <P>SOLUTION: The ink jet recording device has ink jet heads 231 to 234, and printing timing adjusting sections 231Lt to 234Rt. The ink jet heads are each formed of the plurality of head units arranged in a printing width direction orthogonal to a printing direction and allotted to respective colors inclusive of a specific color. The printing timing adjusting sections each function to adjust the printing timing of the head unit such that a printing location of a nozzle at an end of the head unit of the ink jet head for the specific color, and a printing location of a nozzle at an end of the head unit of the ink jet head adjacent to the specific color ink jet head, fall on the same location in the printing direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus in which a plurality of head units provided with a large number of ink ejection ports are arranged to form one ink jet head.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known an ink jet recording apparatus in which a plurality of head units provided with a large number of ink ejection ports are arranged to form one ink jet head, and the plurality of ink jet heads are provided (for example, see Patent Document 1). In Patent Document 1, print timering is controlled so as to correct a nozzle position shift caused by a change in temperature of a print head.
[0003]
Since one ink-jet head is composed of a plurality of head units, there is a case where the inclination of each head unit is different.
[0004]
For this reason, a complicated control is performed by mounting a mechanism for correcting the inclination for each head unit, and hardware and software for controlling the printing position for each nozzle of each head.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-964
[Problems to be solved by the invention]
However, in such a conventional technique, the adjustment is time-consuming and the cost is very high. The present invention has been made in view of the above-described point, and the purpose of the present invention is to increase the number of ink ejection ports. Provided is an ink-jet recording apparatus in which a plurality of head units arranged side by side are arranged to form one ink-jet head, and the printing position can be easily adjusted by adjusting the printing timing of each head unit. Is to do.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, an inkjet head provided for each color including a specific color, and a plurality of head units arranged in a print width direction orthogonal to the print direction, and an inkjet head of a specific color The printing timing of each head unit is adjusted so that the printing position of the nozzle at the end of the unit and the printing position of the nozzle at the end of the adjacent head unit are printed at the same position in the printing direction. A print timing adjustment unit.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a mechanism of the color inkjet recording apparatus. In the figure, reference numeral 11 denotes a main body case 11. A drum 12 that rotates in a direction indicated by an arrow at a constant peripheral speed is provided in the main body case 11. A recording medium 15 such as a recording sheet fed through feed rollers 13 and 14 is wound around the drum 12.
[0009]
That is, a paper feed cassette 16 is provided at the bottom of the main body case 11. The recording medium 15 placed on the placing plate 17 of the sheet cassette 16 is taken out one by one by a feed roller 18 and fed to the feed rollers 13 and 14. Further, a recording medium 15 manually fed from a manual feed tray 19 which is openably and closably mounted on the side of the main body case 11 is fed to the paper feed rollers 13 and 14 by a feed roller 20. Switching between feeding by the feeding roller 18 and feeding by the feeding roller 20 is performed by a feed switching unit 21.
[0010]
A charging roller 22 for adsorbing the recording medium 15 fed from the paper feed rollers 13 and 14 onto the drum surface is disposed opposite to the drum 12. Further, four ink jet recording heads 231, 232, 233, and 234 in which a large number of recording elements are arranged in a line are opposed to the drum 12. Hereinafter, the four ink jet recording heads 231, 232, 233, and 234 are collectively referred to as the ink jet recording head 23. Each of the ink jet recording heads 231 to 234 is incorporated in the printing mechanism 24, and is movable in the rotation axis direction of the drum 12, which is the arrangement direction of the recording elements.
Accordingly, the recording medium 15 is conveyed by the rotation of the drum 12 in a direction (printing direction) substantially orthogonal to the arrangement direction (printing width direction) of the recording elements of the inkjet recording heads 231 to 234.
[0011]
In each of the ink jet recording heads 231 to 234, the recording head 231 ejects cyan (C) ink, the recording head 232 ejects magenta (M) ink, and the recording head 233 ejects yellow (Y) ink. The head 234 ejects black (K) ink. A recording head 231, a recording head 232, a recording head 233, and a recording head 234 are arranged in parallel in a predetermined order from the upstream in the conveying direction of the recording medium 15 wound and conveyed around the drum 12. I have.
Each of the ink jet recording heads 231 to 234 has a large number of ink ejection ports 23a arranged as recording elements at a predetermined pitch.
[0012]
Each of the inkjet recording heads 231 to 234 includes head units 231L, 231C, 231R, 232L,... 234R as shown in FIG.
[0013]
As shown in FIG. 19, the head unit 231L of the inkjet recording head 231, the head unit 232L of the inkjet recording head 232, the head unit 233L of the inkjet recording head 233, and the head unit 234L of the inkjet recording head 234 have the same printing. Having a range. The same applies to other head units.
[0014]
Since the configurations of the inkjet recording heads 231 to 234 are the same, only the configuration of the inkjet recording head 234 will be described with reference to FIGS. 4 and 5.
[0015]
As shown in FIGS. 4 and 5, the ink jet recording head 234 includes three head units 234L, 234C, and 234R provided with a large number of ink ejection ports 23a arranged at a predetermined pitch as recording elements on both sides of a common substrate 234S. It is stuck to. That is, the head unit 234C and the head units 234L and 234R are attached to the central portion on one surface side of the common substrate 234S and the end portion on the other surface side of the common substrate 234S to form a unit. In this printing apparatus, a plurality of head units for one color are bonded to a substrate by bonding, and do not have a structure for performing tilt correction for each head.
[0016]
The positional relationship between the head unit 234C and the head units 234L and 234R is such that all the ink ejection ports are arranged at equal intervals in the arrangement direction.
[0017]
That is, the head unit 234L and the head unit 234C are arranged such that the pitch between the ink ejection ports at the ends adjacent to each other matches the pitch between the ink ejection ports. Further, the head unit 234C and the head unit 234R are arranged so that the pitch between the ink discharge ports at the ends adjacent to each other matches the pitch between the respective ink discharge ports.
[0018]
Note that the ink discharge ports 23a of the head units 234L and 234R and the ink discharge ports 23a of the head unit 234C are not arranged in a straight line in the line direction, whereas the ink discharge ports 23a of the head units 234L and 234R and the ink By adjusting the ejection timing, correction is performed so that the same print result as when the ink ejection ports 23a of the head units 234L, 234C, and 234R are arranged in a straight line is obtained.
[0019]
The printing mechanism 24 includes a reciprocating mechanism 25 on which the ink jet recording heads 231 to 234 are mounted, a motor unit 26 having a reciprocating rod and a linear motor, and a reciprocating means 27. The ink jet recording heads 231 to 234 are made to move forward and backward with respect to the peripheral surface of the drum 12 by the advance and retreat moving means 27. The reciprocating mechanism 25 is controlled to move in the rotation axis direction of the drum 12 by the motor unit 26 to reciprocate each of the ink jet recording heads 231 to 234 in the rotation axis direction of the drum 12, that is, in the recording line direction. It has become.
[0020]
The drum 12 is provided with a peeling claw 28 that can be inserted between the drum surface and the recording medium 15. The recording medium 15 peeled off by the peeling claws 28 is discharged to a recording medium discharge and transport mechanism 29. The recording medium discharge / conveyance mechanism 29 includes a belt conveyor 30 that is in contact with the non-recording surface of the recording medium 15 and a pressing unit 31 that presses the recording medium 15 against the surface of the belt conveyor 30.
[0021]
At the end of the belt conveyor 30, the recording medium 15 conveyed by the belt conveyor 30 is discharged to an upper discharge tray 32 formed on the upper part of the main case 11, or the recording medium 15 is attached to and detached from the side of the main case 11. A direction switch 34 is provided for switching whether or not to discharge to a freely discharge tray 33.
[0022]
In the main body case 11, a main motor 35 for rotating and driving each part, an ink cassette 36 serving as an ink supply source, an ink buffer 37 for temporarily storing ink from the ink cassette 36, and the ink of the ink buffer 37 An ink supply tube 38 and the like to be supplied to the inkjet recording heads 231 to 234 are housed.
[0023]
In the color inkjet recording apparatus having such a configuration, at the time of recording, for example, the recording medium 15 is taken out from the paper supply cassette 16 by the paper supply roller 18 and sent out to the paper supply rollers 13 and 14. Then, the recording medium 15 is fed to the rotating drum 12 by the paper feed rollers 13 and 14 and wound. That is, the recording medium 15 is attracted and wound on the surface of the drum 12 by the charging roller 22.
[0024]
The rotation of the drum 12 causes the recording medium 15 to rotate in the direction in which the ink jet recording heads 231 to 234 are arranged, and the recording medium 15 is transmitted from the ink ejection ports of the ink jet recording heads 231 to 234 to the recording medium 15 at a predetermined timing based on an image signal. And selectively ejects ink of the corresponding color to perform color image recording.
[0025]
FIG. 2 is a block diagram showing the configuration of the entire system. A host computer 41 and a color inkjet recording device 42 are connected by a cable 43. Then, a color image signal is transferred from the host computer 41 to the color inkjet recording device 42.
[0026]
The color inkjet recording apparatus 42 includes a CPU (central processing unit) 421 constituting a control unit main body, a RAM (random memory) provided with a work memory when the CPU 421 performs processing, a temporary storage memory for temporarily storing image signals, and the like. An access memory 422, a ROM (read only memory) 423 storing program data and the like for the CPU 421 to control each section, an interface 424 for transmitting and receiving data to and from the host computer 41, and a printing mechanism 425 are connected. An I / O port 426 is provided.
[0027]
The printing mechanism unit 425 includes a recording head unit 427 including the inkjet recording heads 231 to 234 and a head driving unit 428 that drives the inkjet recording heads 231 to 234 of the recording head unit 427. The printing mechanism 425 is, of course, provided with the printing mechanism 24 described above.
[0028]
The CPU 421 controls the printing mechanism 425 to perform printing. That is, when the CPU 421 receives a color image signal from the host computer 41, the CPU 421 temporarily stores the image signal in the RAM 422, performs image processing on the image signal, supplies it to the printing mechanism 425, and records the color image on the printing mechanism 425. The operation is performed.
[0029]
The head drive unit 428 has timers for each of the inkjet recording heads 231 to 234, the number of which is equal to the number of head units. In this embodiment, since each of the four ink jet recording heads is composed of three head units, it has 4 × 3 = 12 timers.
[0030]
FIG. 3 shows three timers for the black (B) inkjet recording head 234. In FIG. 3, 234Lt is a timer for outputting a print timing signal of the head unit 234L of the ink jet recording head 234, 234Ct is a timer for outputting a print timing signal of the head unit 234C, and 234Rt is a timer for outputting a print timing signal of the head unit 234R. It is.
[0031]
The timers 234Lt, 234Ct, and 234Rt each output a print timing signal after the set values BL, BC, and BR have elapsed from the input of the print start signal. The ink is ejected from the head units 234L, 234C, and 234R according to the print timing signal.
[0032]
Similarly, each of the ink jet recording heads 231 to 233 has three timers 231Lt, 231Ct, 231Rt, timers 232Lt, 232Ct, 232Rt, timers 233Lt, 233Ct, and 233Rt. The function of each timer is the same as that of the ink jet recording head 234.
[0033]
Next, positioning will be described.
[0034]
(1) First, black alignment having characteristics such as high frequency of use and use as ruled lines is performed. As a characteristic of human eyes, there is a characteristic that a case where a step is suddenly generated is more conspicuous than a case where a straight line is gently inclined. Even if the color is not black, the color may be realized in the most prominent color or the frequently used color.
[0035]
Hereinafter, a case will be described in which the left head unit 234L of the inkjet recording head 234 rises to the right, the center head unit 234C rises to the right, and the right head unit 234R falls to the right.
[0036]
FIG. 8 shows a case where the print timing is adjusted so that the print positions at the joints of the head units 234L, 234C, and 234R are the same. Down arrows A and B correspond to joints. In this case, the Y coordinate error [ΔY2] between the left end and the right end of the print is large, but it looks straight to human eyes.
[0037]
FIG. 7 shows a case where the printing timing is adjusted so as to minimize the Y coordinate error [ΔY1] between the left end and the right end of the printing. Down arrows A and B correspond to joints. In this case, a step is seen at the printing portion at the joint between the left head unit 234L and the central head unit 234C.
[0038]
In this manner, the method of adjusting the Y coordinate of the printing center portion of each black head to minimize the Y coordinate error has a disadvantage that a step occurs at the joint of the head units and is visually conspicuous.
[0039]
Therefore, in the present embodiment, the right end of the head unit 234C arranged at the center of the print width and the left end of the right head unit 234R, and the left end of the head unit 234C arranged at the center of the print width and the left head unit 234L The print start timing of the right and left head units 234R and 234L adjacent to the head unit 234C which is electrically arranged at the center of the print width is adjusted so that the print position with respect to the Y axis at the right end of the right side becomes the same position. ing.
[0040]
FIG. 9A shows a print image when the black inkjet recording head 234 having the configuration shown in FIGS. 4 and 5 is printed with a shift by a predetermined time Δt. FIGS. 9B to 9D show the drive timing at this time. At the time of High, the ink is ejected and printed on the recording paper 15.
[0041]
At the left end (A portion) of the right head unit 234R with respect to the right end of the central head unit 234C, the right end of the central head unit 234C is disposed above in the drawing. This indicates that printing is performed as shown in FIG. 9A when the center head unit 234C is driven ahead of the right head unit 234R by a predetermined time Δt. In other words, if the drive is shifted by the predetermined time Δ as it is, the joint between the right end of the central head unit 234C and the left end of the right head unit 234R will be blind. This large cause is affected by the amount of adhesive and the thickness balance of the left and right ends of the head when the head units 234L, 234C, and 234R are attached to the substrate 234S.
[0042]
In this case, the printing position of the right head unit 234R is delayed by Δt1 with respect to the center head unit 234C by Δt1, so that the printing positions of the right end of the center head unit 234C and the left end (B portion) of the right head unit 234R are the same Y coordinate, that is, Adjust so that it is at the same position with respect to the printing direction, so that the step at the joint is inconspicuous.
[0043]
Similarly, the step between the print position at the left end of the central head unit 234C and the print position at the right end of the left head unit 234L is adjusted. In this case, as shown in FIG. 10B, the printing timing of the left head unit 234L is advanced by Δt2 with respect to the center head unit 234C, thereby printing the left end of the center head unit 234C and the right end of the left head unit 234L. The position (portion C) is adjusted so as to be at the same Y coordinate, that is, the same position with respect to the printing direction, so that the step at the joint is inconspicuous. Here, Δt1 is an adjustment value of the head unit 234R for the head unit 234C, and Δt2 is an adjustment value of the head unit 234L for the head unit 234C. These adjustment values Δt1 and Δt2 are set separately.
[0044]
Although the black straight line after the adjustment has a slope as shown in FIG. 10A, such a straight line with a large slope does not feel visually bent.
[0045]
The adjustment of the printing timing as described above is performed by printing the test pattern of the black inkjet recording head 234 on the recording paper 15. Then, referring to this test pattern, the set value BL for the head unit 234L, the set value BC for the head unit 234C, and the set value BR for the head unit 234R are set in the timers 234Lt, 234Ct, and 234Rt.
[0046]
(2) Next, alignment of cyan and other colors is performed. FIG. 11 shows the printing result of each color at a predetermined timing. The description will be made by taking the cyan ink jet recording head 231 as an example.
[0047]
In this case, as in the case of the above (1), the step between the right end of the left head unit 231L and the left end of the central head unit 231C, and the joint between the right end of the central head unit 231C and the left end of the right head unit 231R are made inconspicuous. Rather than making adjustments, adjustments are made for the black head units 234L, 234C, and 234R that are printed in the same print range.
[0048]
This is because cyan, magenta, and yellow are rarely printed in a single color, and since they are used in a mixed color, there is a phenomenon that a step of a joint is hardly noticeable in a mixed color image such as a ruled line seen in black. is there.
[0049]
When these colors are adjusted as shown in FIG. 12 so as to make the steps of the joints inconspicuous as in the case of black, the inclination of each head of each color varies. For this reason, as shown in FIG. 13, even if the printing positions of the respective colors are aligned at a certain position (the black center in the present embodiment), a portion where the printing deviation is large occurs when the entire page is viewed. . Therefore, when a uniform color is printed in a page, a phenomenon that the color looks different depending on the location is likely to occur.
[0050]
Here, in the present invention, the centers of the head units 231L to 233L, 231C to 233C, 231R to 233R of the other colors having the same print range as the centers of the black head units 234L, 234C, and 234R are printed at the same position. The print timing of each head unit for the other colors is adjusted as described above.
[0051]
The adjustment of the print timing of the black inkjet recording head 234 and the cyan inkjet recording head 231 will be described with reference to FIG.
[0052]
First, the cyan central head unit 231C is set so that the center of the central head unit 234C of the black inkjet recording head 234 and the center of the central head unit 231C of the cyan inkjet recording head 231 are at the same printing position in the printing direction. Adjust the print timing of.
[0053]
Similarly, the printing timing of the cyan right head unit 231R is adjusted so that the center of the black right head unit 234R and the center of the cyan right head unit 231R are at the same printing position in the printing direction.
[0054]
Further, the printing timing of the cyan left head unit 231L is adjusted so that the center of the black left head unit 234L and the center of the cyan left head unit 231L are at the same printing position in the printing direction.
[0055]
The above adjustment is performed by comparing test patterns of the black inkjet recording head 234 and the cyan inkjet recording head 231. Then, as shown in FIG. 18, the set values CL, CC, and CR are set in the timers 231Lt, 231Ct, and 231Rt for the cyan inkjet recording head 231 respectively.
[0056]
In this case, when viewed alone with the cyan head units 231R, 231C, and 231L, there is a step at the joint between the head units.
[0057]
As described above, the printing positions of the cyan head unit and the black head unit were adjusted, but printing between the head unit having the same printing range of magenta and black and printing between the head units having the same printing range of yellow and black were performed. The adjustment of the position is performed in the same manner, and the set values ML,..., YR are set in the timers 232Lt to 233Rt for the magenta inkjet recording head 232 and the yellow inkjet recording head 233.
[0058]
The resulting printing position arrangement is shown in FIG. 15 (black and magenta) and FIG. 16 (black and yellow). Since it is difficult to understand if all four colors are represented by one, it is described based on black.
[0059]
FIG. 17 summarizes all colors. 17 and FIG. 13, it can be seen that the color shift is smaller in FIG.
[0060]
Although the above example describes the case where each color head unit prints at the same position with respect to the print position, a structure in which the ends of the head units are partially overlapped within the color as shown in the F portion of FIG. A similar effect can be obtained even in a structure in which two heads perform division printing at an overlapped portion so as to make the step at the joint inconspicuous.
[0061]
In the above-described embodiment, the central head unit is arranged on the upstream side in the sheet conveying direction. However, the central head unit may be arranged on the downstream side in the sheet conveying direction, or an even number of head units may be arranged. Even in this case, the step of the joint can be similarly made inconspicuous.
[0062]
In the above-described embodiment, one inkjet recording head 23 is composed of three head units, and one such inkjet recording head 23 is provided for each color, that is, a total of four inkjet recording heads are provided. is not. That is, one ink jet recording head 23 may be constituted by a plurality of head units, and one ink jet recording head 23 may be provided for each of a plurality of colors.
[0063]
Further, the present invention can be applied to a monochrome ink jet recording apparatus having only the black ink jet recording head 234.
[0064]
【The invention's effect】
As described above in detail, according to the present invention, the print timing of each head unit is adjusted in an ink jet recording apparatus in which a plurality of head units provided with a large number of ink ejection ports are arranged to form one ink jet head. Accordingly, it is possible to provide an ink jet recording apparatus capable of easily performing printing position alignment.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a mechanical unit of an inkjet recording apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of the entire system according to the embodiment;
FIG. 3 is a diagram showing a configuration of a print timing adjustment unit according to the embodiment.
FIG. 4 is a perspective view showing the appearance of the inkjet recording head according to the embodiment.
FIG. 5 is a diagram showing a positional relationship between ink ejection ports of each head unit in the ink jet recording head of the embodiment.
FIG. 6 is a diagram showing a relationship between the arrangement of the inkjet recording heads and a recording paper conveyance direction in the embodiment.
FIG. 7 is a view showing a printing example when the printing timing is adjusted so as to minimize the Y coordinate error between the left end and the right end of the printing of the inkjet recording head in the embodiment.
FIG. 8 is a diagram showing a printing example when the printing timing is adjusted so that the printing position at the joint of each head unit in the ink jet recording head of the embodiment is the same position.
FIG. 9 is a diagram showing a print image and drive timing when printing is performed by shifting the ink jet recording head according to the embodiment by a predetermined time.
FIG. 10 is a diagram showing a print image and drive timing after adjustment is made so as to make the step of the joint inconspicuous in the ink jet recording head according to the embodiment.
FIG. 11 is a diagram showing a printing result at a predetermined timing of each color when performing alignment of other colors such as cyan in the ink jet recording head according to the embodiment.
FIG. 12 is a diagram showing a print image after adjustment is made so as to make a step of a joint of each color inconspicuous in the ink jet recording head according to the embodiment.
FIG. 13 is a view showing a print image in which the print positions of the respective colors are adjusted when the ink jet print head according to the embodiment is adjusted so as to make the steps of the joints of the respective colors inconspicuous.
FIG. 14 is a diagram showing a print image when black and cyan are adjusted in the inkjet recording head according to the embodiment.
FIG. 15 is a diagram showing a print image when black and magenta are adjusted in the inkjet recording head according to the embodiment.
FIG. 16 is a diagram showing a print image when black and yellow are adjusted in the inkjet recording head according to the embodiment.
FIG. 17 is a diagram showing a print image in which all colors are combined after adjusting each color in the inkjet recording head according to the embodiment.
FIG. 18 is a diagram illustrating a configuration of a print timing adjustment unit according to the embodiment.
FIG. 19 is a view for explaining the arrangement of head units constituting each of the ink jet recording heads 231 to 234.
FIG. 20 is a diagram showing an example in which nozzle positions are partially overlapped between head units.
[Explanation of symbols]
231 to 234: inkjet recording heads, 234L, 234C, 234R: head unit, 41: host computer, 42: color inkjet recording apparatus.

Claims (9)

An inkjet head provided for each color including a specific color configured by arranging a plurality of head units in a printing width direction orthogonal to the printing direction,
The print timing of each head unit is set so that the print position of the nozzle at the end of the head unit of the inkjet head of the specific color and the print position of the nozzle at the end of the adjacent head unit are printed at the same position in the printing direction. An ink jet recording apparatus, comprising: a print timing adjusting unit configured to adjust. The print timing adjustment unit is provided for each head unit, has a timer unit that starts a counting operation when a print start signal is input, and outputs a print timing signal when the count value reaches a set value. 2. The ink jet recording apparatus according to claim 1, wherein the print timing of each head unit is adjusted by changing a set value set in the ink jet recording apparatus. Further, the heads of the other color ink jet heads have the same print range as the head unit of the specific ink jet head, so that the printing positions at the center portions of the head units of the other color ink jet heads are the same in the printing direction. 2. The ink jet recording apparatus according to claim 1, further comprising a print timing adjusting unit configured to adjust a print timing of the unit. The print timing adjustment unit is provided for each head unit, has a timer unit that starts a counting operation when a print start signal is input, and outputs a print timing signal when the count value reaches a set value. 4. The ink jet recording apparatus according to claim 3, wherein the print timing of each head unit is adjusted by changing the set value set in the above. 4. The ink jet recording apparatus according to claim 1, wherein the specific color is black. 4. The ink jet recording apparatus according to claim 1, wherein the specific color is a color that is most easily seen. 4. The ink jet recording apparatus according to claim 1, wherein the specific color is a frequently used color. 2. The ink jet recording apparatus according to claim 1, wherein an end of a head unit constituting the ink jet head is arranged so as not to overlap a nozzle at an end of an adjacent head unit. 2. The ink-jet recording apparatus according to claim 1, wherein an end of the head unit constituting the ink-jet head partially overlaps a nozzle at an end of an adjacent head unit.

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