JP2003266823A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thinner thermal printer. <P>SOLUTION: The thermal printer comprising a supporting member 1 having a pair of side plates 1b disposed oppositely on a substrate 1a, a platen 11 disposed oppositely to a thermal head 10, and an idle roller 7 and a drive roller 8 for carrying a paper P is further provided with a sliding section 13 operating to move the platen 11 between a print position and a retreat position through a transmission member 12, and a section 15 for transmitting a power to a section 14 being applied with an action power to the action force sliding section 13 wherein the transmitting section 15 is arranged to pass between the drive roller 8 and the substrate 1a. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer.

[0002]

2. Description of the Related Art In a thermal printer having a thermal head and a platen arranged so as to face the thermal head, a recording medium and a recording ribbon to be printed are interposed between the thermal head and the platen to perform thermal transfer or heat transfer. A thermal printer configured to print by sublimation has been put into practical use. In particular, a thermal printer that performs color printing is configured such that the recording medium is conveyed in the forward and reverse directions by a conveying roller, the recording ribbon is supplied and wound, and color printing is performed for each YMC color.

In order to carry the recording medium and wind the recording ribbon in this way, it is necessary to provide a moving mechanism for moving either one of the thermal head and the platen from the printing position to the retracted position. In order to reduce the size of the thermal printer, the conventional moving mechanism is provided with an operating mechanism that moves the platen or the thermal head to the platen or the thermal head with the transport roller interposed therebetween, and the drive source on the opposite side. And an operating force urging mechanism for activating the operating force from the drive source.

At present, a plate-shaped power transmission member for transmitting the operating force from the operating force urging mechanism to the operating mechanism is provided along the side surface of the printer case.

[0005]

However, with the spread of mobile devices, a portable and thin thermal printer has been demanded. In the conventional thermal printer, since the power transmission member is provided along the side surface of the printer case, there is a problem that the entire printer cannot be sufficiently thinned.

More specifically, the power transmission member is required to have a certain strength and to have an appropriate width in order to ensure the function of transmitting the operating force. For this reason,
The thickness of the printer (width of the side surface of the printer case) is limited to the width of the power transmission member, and the thickness cannot be sufficiently reduced.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a thinner thermal printer.

[0008]

[Means for Solving the Problems]
In order to achieve the object, the thermal printer of the present invention is
A supporting member having a substrate and a pair of side plates provided on the substrate and facing each other; a thermal head; a platen facing the thermal head; and a thermal head supported by the side plates of the supporting member, In a thermal printer including a conveyance roller that conveys an object to be printed between the platen and a movement unit that moves the platen between a printing position and a retracted position, the movement unit is configured to move the conveyance roller with respect to the conveyance roller. And an operating force urging portion that is disposed on the opposite side of the platen and that applies an operating force, and is disposed on the platen side with respect to the transport roller, and the platen is provided between the printing position and the retreat position. And a transmission portion that transmits the operating force urged by the operating force urging portion to the operating portion. It is characterized in that it is arranged to pass between the transport roller and the substrate.

Further, the thermal printer of the present invention includes a support member having a substrate and a pair of side plates provided on the substrate and opposed to each other, a thermal head, a platen opposed to the thermal head, and A conveyance roller that is supported by the side plate of the support member and that conveys an object to be printed between the thermal head and the platen, and a moving unit that moves the thermal head between a printing position and a retreat position. In the thermal printer, the moving means is disposed on the side opposite to the thermal head with respect to the transport roller, and an operating force urging portion for activating an operating force,
The operating unit is disposed on the thermal head side with respect to the transport roller, and is operated by the operating unit that operates to move the thermal head between the printing position and the retracted position, and is biased by the operating force biasing unit. And a transmission unit configured to transmit the actuation force to the actuation unit, the transmission unit being disposed so as to pass between the transport roller and the substrate.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an external perspective view (partially omitted) of a thermal printer A according to a first embodiment of the present invention. Further, FIG. 2 is a configuration diagram of a main part of the thermal printer A, in which (a) shows a mode during printing and (b) shows a mode during non-printing.

Referring to FIG. 1, the thermal printer A is
It has a supporting member 1 and a thermal head supporting member 16 rotatably attached to the supporting member 1. Support member 1
Has a substrate 1a and a pair of side plates 1b provided on the substrate 1a and opposed to each other, and constitutes a case body having a U-shaped cross section. The substrate 1a and the side plate 1b can be integrally formed from a sheet metal, for example, and in this case, the side plate 1b can be formed by bending both ends of the sheet metal. The thickness H (see FIG. 2) of the thermal printer A is determined by the height (width) of the side plate 1b, and the smaller the width of the side plate 1b, the thinner the thermal printer A can be made. it can.

The thermal head support member 16 is rotatably supported by a shaft body 17 provided between the ends of the pair of side plates 1b. Further, the thermal head support member 16 includes
The thermal head 10 is mounted. In FIG. 1, the thermal head support member 16 is shown opened to the support member 1, but when used, the thermal head support member 16 is closed by the lock mechanism 52 shown in FIG. 1 as shown in FIG. It is locked and used. As shown in FIG. 1, by opening the thermal head supporting member 16 with respect to the supporting member 1, the heat generating portion 10a of the thermal head 10 can be inspected and cleaned, and the recording ribbon R described later can be replaced. Become.

Further, as shown in FIG. 2, at the time of use, a doorway 5 surrounded by the support member 1 and the thermal head support member 16 is formed, and through this doorway 5 in the direction of arrow d in the figure. The paper P that is the material to be printed is introduced into the printer with the printing surface facing up.

Next, the support member 1 is provided with an idle roller 7 and a drive roller 8 as a transport roller for transporting the paper P introduced from the entrance / exit 5. The idle roller 7 and the drive roller 8 are rotatably supported by bearings (not shown) provided on each side plate 1b. In order to follow the idle roller 7 with respect to the drive roller 8 without displacement, a pressure contact mechanism (not shown) is provided near the bearing. With this configuration, the drive roller 8 and the idle roller 7
The slip in the nip portion between them is prevented, and the paper is conveyed in the forward and reverse directions.

The support member 1 is provided with a platen 11 via a second rotating member 21 and a connecting portion 21a.
As shown in FIG. 2, the platen 11 is provided so as to face the thermal head 10 when used. The platen 11 is made of, for example, a heat-resistant elastic material such as silicon rubber having a predetermined hardness, and is formed in a plate shape so as to have a semi-cylindrical cross section as shown in the present embodiment. It is also possible to configure.

Next, as shown in FIG. 2, in order to perform printing by thermal transfer or thermal sublimation, a supply spool 3 and a take-up spool 4 are detachably provided on the support member 1, and one point of these is provided. A recording ribbon R shown by a chain line is wound. The recording ribbon R is printed on the base film as a screen 1
Solid ink layers of three primary colors, yellow (Y), magenta (M), and cyan (C), each ink layer having an area corresponding to the area of one sheet is laid, and all colors can be reproduced by additive color mixing. In addition to the above, an overcoat layer forming a protective layer is formed.

The recording ribbon R is provided so as to pass between the heat generating portion 10a of the thermal head 10 and the platen 11 as shown in the figure. Then, the paper P is also transferred to the thermal head 10 by the idle roller 7 and the drive roller 8.
The ink is conveyed between the heat generating portion 10a and the platen 11, and the heat generated by the heat generating portion 10a sublimes the ink applied to the recording ribbon R, and an image or the like is printed on the paper P.

Here, when each color is printed by the recording ribbon R, it is necessary to reciprocate and convey the paper P for each color. In this case, the platen 11 is moved from the printing position shown in FIG. 2A to the retracted position shown in FIG. 2B, the paper P is conveyed in the forward and reverse directions, and the recording ribbon R is moved.
Supply and wind. Hereafter, platen 1 like this
A movement mechanism for moving 1 between the printing position and the retracted position will be described.

In this embodiment, the moving mechanism of the platen 11 is composed of an operating portion, an operating force urging portion, and a transmitting portion.

First, a pair of second rotating members 21 and a connecting portion 21a fixed between them are provided as operating portions. The second rotating member 21 and the connecting portion 21a are arranged closer to the platen 11 than the idle roller 7 and the driving roller 8 that form the conveying roller, and the platen 11 is supported on the connecting portion 21a. The platen 11 is, for example,
It is fixed to the upper surface of the connecting portion 21a with an adhesive or the like.
The second rotating member 21 includes a shaft body 22 provided between the side plates 1b.
It is rotatably supported around the platen 11, and the rotation causes the platen 11 to move between the printing position in FIG. 2A and the retracted position in FIG. 2B.

As shown in FIG. 2, a sliding portion 13 having a downwardly convex shape is provided on the lower surface side of the connecting portion 21a. In the case of this embodiment, the sliding portion 13 is connected to the connecting portion 21a.
However, it may be fixed to the connecting portion 21a as a separate member.

Further, as shown in FIG. 1, two torsion springs 29 are provided around the shaft body 22 which pivotally supports the second rotating member 21, and the second rotating member 21 is provided on the substrate. It constantly urges toward the 1a side to prevent backlash.

Next, as shown in FIG. 1, a pair of first rotating members 20 are provided as actuating force urging portions. The configuration will be described below with reference to FIG. 3A, which is a cross-sectional view taken along the line YY of FIG. 2B, and FIG. 4, which is a cross-sectional view taken along the line XX of FIG. 2A. To do. Note that, in FIGS. 3A and 4, the connecting portion 21a provided between the pair of second rotating members 21 is shown broken away from the middle. Further, FIG. 3 (b) is similar to FIG. 3 (a).
FIG. 3 is a functional diagram of FIG.

The pair of first rotating members 20 are arranged on the inlet / outlet 5 side, which is opposite to the platen 11 with respect to the idle roller 7 and the driving roller 8 which constitute the conveying roller.
The first rotating member 20 is a member that urges an operating force for rotating the second rotating member 21.

The first rotating members 20 and 20 are formed as a pair of link members as shown in the drawing, and are connected to each other at their ends by a shaft support 32 so as to be rotatable with respect to each other. . Further, in the pair of shaft supporting portions 33 provided on the substrate 1a, intermediate portions are pivotally supported respectively. Therefore, each of the first rotating members 20 rotates around the shaft supporting portion 33, but when one rotating member 20 rotates, the other rotating member 20 also rotates via the shaft supporting portion 32. Becomes

A tension spring 37 for urging the end of one of the first rotating members 20 and the side plate 1b is urged to move the end in the direction of the arrow in FIG. A tooth portion 35 is formed at the end of the first rotating member 20. The drive gear 36 is a gear driven by a mechanism to be described later, and for transmitting an operating force for rotating the second rotating member 21 to the first rotating member 20 via the tooth portion 35. The gear has teeth formed only at a predetermined angle. here,
The drive gear 36 is rotated by receiving a drive force from the drive source M2, and rotates the first rotation member 20 in a range where the drive gear 36 meshes with the tooth portion 35. In addition, the tension spring 37, after the engagement is released,
The first rotating member 20 in the free state is urged to return to the original position.

Referring to FIG. 3, rotation of the drive gear 36 in the counterclockwise direction causes the teeth to move to the right, and the first rotating member 20 on the front side of the drawing rotates in the counterclockwise direction. , The other first rotation member 20 is also rotated in association with this, and both of them are shown in FIG. 4 from the inverted "U" shape shown in FIG.
Further, when the drive gear 36 rotates, the engagement with the tooth portion 35 is disengaged, and the first rotating member in the free state is pulled by the tension spring 37 in the direction of the broken line in FIG. 3B.
Will be urged by and will return to the state of FIG.

Next, the transmission section will be described. With reference to FIG. 1, FIG. 2, FIG. 3A, FIG. 3B, and FIG. 4, in this embodiment, a transmission member 12 is provided as a transmission unit. Transmission member 1
2 is formed in a plate shape, and is made of a metal plate made of an elastic material such as stainless steel or phosphor bronze.

The transmission member 12 is disposed so as to pass between the drive roller 8 constituting the conveyance roller and the substrate 1a, and the pair of left and right first end portions 30b which is one end portion of the transmission member 12. Is a first rotating member 20 that constitutes an operating force urging portion.
It is rotatably supported by the shaft support portion 34. In addition, at the other end of the transmission member 12, the three second end portions 3 are provided.
0a is formed. The second end 30a is a leaf spring having a shape protruding upward as shown in FIG. Further, a pair of left and right elongated holes 30c is further provided at the other end of the transmission member 12, and the stud 31 fixed to the board 1a is inserted through the elongated hole portion 30c.
I am trying to guide you in the movement.

Next, the operation of the moving mechanism of the platen 11 will be described with reference to FIGS. 3 (a), 3 (b) and 4. Figure 3
In (a), the pair of first rotating members 20 forming the actuating force urging portion are arranged in an inverted "U" shape. At this time, as shown in FIG. 3A, the platen 11 is in the retracted position. In this state, the drive gear 36 is rotated counterclockwise, and the pair of first rotating members 20 are "turned" as shown in FIG.
It is transformed into the shape of.

Then, the transmission member 12 pivotally supported by the pivotal support portion 34 of the first rotating member 20 is pulled by the first rotating member 20 and moves to the right side of the drawing as a whole. At this time, the transmission member 1
The second end 30a of 2 also moves to the right side of the drawing, and the sliding portion 13 of the connecting portion 21a that constitutes the operating portion moves to the second portion of the transmission member 12.
It rides on the end portion 30a, the second rotating member 21 rotates, and the platen 11 moves upward to the printing position as shown in FIG. 2 (a). At this time, since the transmission member 12 has elasticity, the platen 11 is not excessively pressed by the thermal head 10.

Subsequently, when the drive gear 36 is rotated, the meshing of the intermittent gear is disengaged, so that the drive gear 36 becomes free, and the urging force of the tension spring 37 causes the first rotating member 20 to move.
It is transformed from the "ku" shape of No to the inverted "ku" shape shown in FIG. Then, the transmission member 12 axially supported by the shaft supporting portion 34 of the first rotating member 20 is pressed by the first rotating member 20 and moves to the left side in the figure as a whole. At this time, the second end portion 30a of the transmission member 12 also moves to the left side of the drawing, the connecting portion 21a riding on the second end portion 30a of the transmission member 12 descends, and
The rotating member 21 rotates and the platen 11 moves down to the retracted position as shown in FIG.

Thus, in this embodiment, the transmission member 12
Is guided by the reciprocating movement of the second end portion 30a of the second rotating member 2
1 rotates, and the platen 11 moves between the printing position and the retracted position. Here, in the present embodiment, the transmission member 12 is configured to pass between the drive roller 8 that constitutes the transport roller and the substrate 1a. The advantage thereof is that even if the width of the transmission member 12 is increased to secure the strength of the transmission member 12 as in the present embodiment, the thickness of the thermal printer A is not affected and the thickness can be reduced. In addition, here, the intermittent gear is used as the drive gear 36, and the reciprocating operation of the transmission member 12 is performed in cooperation with the tension spring 37. However, it is also possible to configure only the forward and reverse rotations of the drive motor. Is.

Next, the drive source of the thermal printer A will be described. In order to reduce the size of the device, the drive source is arranged closer to the entrance / exit 5 side than the idler roller 7 and the drive roller 8 which constitute the transport roller, on the side opposite to the platen 11 in view of the layout.

FIG. 5 is a plan view showing a state in which the motor M2 as a drive source and the motor M1 are fixed to the side plate 1b. As shown in FIG. 5, the drive gear 36 is axially supported by bearings provided on the side plate 1b and a bracket 45 shown by hatching. The motor M2 is a worm wheel 3
A worm gear 38 meshing with the gear 9 is fixed to the output shaft.

A member pivotally supporting a planetary gear 40 is rotatably provided around the rotation axis of the worm wheel 39, and the planetary gear 4 is driven by the forward and reverse driving of the motor M2.
Move 0 left and right. As a result, either the drive gear 41 or the recording ribbon winding gear 42 is connected to the planetary gear 40.
By bringing the platen 11 into a meshed state with one, it is possible to move the platen 11 and wind the recording ribbon with one motor M2.

That is, by engaging the planetary gear 40 and the drive gear 41 with each other, the driving force of the motor M2 is transmitted to the first rotating member 20. As described above, the reciprocating movement of the transmitting member 12 causes the platen 11 to move. It is possible to move.

The motor M1 is fixed to the side plate 1b by a bracket 44, and a stepping motor is used to form an image by driving the drive roller 8 via a gear. With reference to FIG. 2, these motors M1 and M2 are selected from motors having a flat portion as shown in the drawing, and the shape of the bracket is made as shown so that the whole is made as flat as possible.

Next, the printing operation of the thermal printer A having the above construction will be described.

With the above construction, in the retracted position state shown in FIG. 2B, the paper P is conveyed at the nip portion between the idle roller 7 and the drive roller 8 and sent to the print start position for one screen. The rear end portion corresponding to the length is continued until it is determined that the heat generating portion 10a and the platen 11 are clamped, and the cue and the clamped state are maintained. Before and after this, cueing is performed to detect the start position of the Y color layer of the recording ribbon R.

Subsequently, when the motor M2 is energized, the thermal head 10 is brought into contact with the platen 11 with the recording ribbon R interposed therebetween, ready for printing start, and synchronized with the winding operation of the recording ribbon R. Then, the paper P is conveyed in the opposite direction, and in synchronization with this, the thermal head 10 is energized for a predetermined period of time to start the formation of the first color print, and the first one-screen print is completed.

Following this, the nip portion between the drive roller 8 and the idle roller 7 is surely held and conveyed in the forward and reverse directions to perform a plurality of reciprocating drives required for color printing, thereby The printing is completed and the sheet is discharged from the doorway 5.

The thermal printer constructed as described above can be used as a recording device for printing directly from, for example, a digital camera or a mobile phone. It goes without saying that the printing is not limited to the above-mentioned color printing and may be, for example, a monotone printing. In this case, since a black layer printing using a recording ribbon or a thermal paper can be used, higher speed can be realized.

Next, FIG. 6 is a front view of the main part of the second embodiment of the thermal printer. In addition, FIG.
6 is a plan view of the transmission member 12. FIG. Further, FIG. 7B is a cross-sectional view taken along the line XX of FIG. 7A.

In FIG. 6 and FIG. 7, the components already described are given the same reference numerals and the description thereof is omitted, and the different parts will be described below.

First, the second rotating members 21 and 21 to which the platen 11 is fixed are rotatably supported by the shafts 46 and 46 fixed to the left and right side plates 1b and 1b, and between the second rotating members 21 and 21 and the substrate 1a. The tension spring 50 is provided so as to obtain an urging force that rotates upward. Pins 47 serving as operating parts are fixed to the second rotating members 21 and 21 at the positions shown in the drawing.

With the above construction, the platen 11 is pressed by the urging force of the tension spring 50 in a state where the platen 11 is always in contact with the thermal head 10.
However, the thermal head 10 is not excessively pressed.

On the other hand, the transmission member 12 is integrally formed with side plates 12a and 12a which are bent and formed.
In 2a and 12a, a shaped portion 48 having an inclined surface into which the pin 47 is embedded is formed.

According to the above-mentioned structure, the pin 47 embedded in the shape portion 48 is moved downward from the state shown in FIG. 7 as the transmission member 12 is moved as shown in FIG. Therefore, the second rotating member 21 is rotated in the arrow direction as shown in FIG. 8B against the biasing force of the tension spring 50, so that the platen 11 is separated from the thermal head. be able to.

According to this structure, since the operating portion which is the pin 47 and the operating force urging portion which is the shape portion having the inclined surface can be provided on both side surfaces, the height dimension H can be further reduced. Like

Finally, FIG. 9 is an external perspective view of the thermal printer according to the third embodiment of the present invention. In the figure, the same reference numerals are given to the components already described, and the description will be omitted to describe the different configurations.

First, a platen support member 160 is provided rotatably with respect to the support member 1 by a shaft 17 in place of the above-mentioned thermal head support member.

The thermal head 10 is fixed to the connecting portion between the second rotating members 21 and 21.
It is configured to be driven in the vertical direction as the plate member 30 moves.

With the above construction, the height dimension H can be made thin within the external dimensions of the thermal printer, and
The pressing force of the platen on the thermal head can be prevented from becoming excessive. Further, the ribbon cartridge 60 containing the recording ribbon R can be set from the state shown in the figure.

[0055]

As described above, according to the present invention,
It is possible to provide a thinner thermal printer.

[Brief description of drawings]

FIG. 1 is an external perspective view of a thermal printer A according to a first embodiment of the present invention.

2 is a configuration diagram of a main part of a thermal printer A, FIG.
(A) shows a mode during printing, and (b) shows a mode during non-printing.

3 (a) is a sectional view taken along the line YY of FIG. 2, and FIG. 3 (b) is
It is a functional diagram of the ZZ line arrow of Drawing 3 (a).

FIG. 4 is a sectional view taken along line XX of FIG.

FIG. 5 is a plan view showing a state in which a motor M2 that is a drive source and a motor M1 are fixed to a side plate 1b.

FIG. 6 is a front view of a main part of a thermal printer according to a second embodiment.

7A is a plan view showing the plate member 30 with the connecting portion 21a of the second rotating member 21 of the platen 11 removed. FIG.
8B is a cross-sectional view taken along the line XX of FIG. 8A.

FIG. 8A is a plan view for explaining the operation of the plate member,
8B is a cross-sectional view taken along the line XX of FIG. 8A.

FIG. 9 is an external perspective view of a thermal printer according to a third embodiment of the present invention.

[Explanation of symbols]

A thermal head printer 1 Support member 1a substrate 1b Side plate 3 supply spools 4 take-up spool 5 doorways 7 Idle roller (conveyor roller) 8 Drive roller (conveyor roller) 10 thermal head 11 Platen 12 Moving member 13 Working part 14 Actuating part 15 Transmitter 16 Thermal head support member 20 First rotation member 21 Second rotation member 29 Torsion spring 33 Second shaft support 34 First shaft support 35 teeth 36 Drive gear M1, M2 motor P paper R recording ribbon H height dimension

Continued front page    F term (reference) 2C058 AB02 AC06 AE02 AF31 DA11                       DA18 DA21 DC02 DC04 DC25                 2C064 CC03 EE02                 2C065 AA01 AB01 AC04 AD03 CC02                       CC05 CC10 CC13 CC24 CC25                       CC26 CC27 CC28

Claims (4)

[Claims] 1. A support member having a substrate and a pair of side plates provided on the substrate and opposed to each other; a thermal head; a platen opposed to the thermal head; and supported on the side plates of the support member. A thermal printer that includes a transport roller that transports an object to be printed between the thermal head and the platen, and a moving unit that moves the platen between a printing position and a retreat position. An operating force urging portion that is disposed on the side opposite to the platen with respect to the transport roller and that applies an operating force; and a platen side that is disposed on the platen side with respect to the transport roller. An operating unit that operates to move between the retracted position and a transmitting unit that transmits the operating force urged by the operating force urging unit to the operating unit. The transmission unit, thermal printer, characterized in that in passing between the substrate and the conveying rollers are arranged. 2. The thermal head supporting member for supporting the thermal head is further provided, and the thermal head supporting member is rotatably attached to the supporting member. Thermal printer. 3. The operating force urging unit includes a first rotating member that is rotated by an urging force from a drive source, the operating unit supports the platen, and moves the platen to the printing position. A second rotation member that rotates so as to move between the retracted position and the retracted position, wherein the transmission portion is connected to the first rotation member, and the first end portion on the operating force urging portion side; A plate-like member that reciprocates in accordance with the rotation of the first rotating member, which has a second end portion on the side of the operating portion on which a convex portion that is in sliding contact with the second rotating member is formed. The thermal printer according to claim 1, wherein the second rotating member is rotated by being guided by the movement of the convex portion due to the reciprocating movement of the plate-shaped member. 4. A support member having a substrate and a pair of side plates provided on the substrate and opposed to each other; a thermal head; a platen opposed to the thermal head; and supported on the side plates of the support member. And a moving roller for moving the printed material between the thermal head and the platen, and a moving means for moving the thermal head between a printing position and a retracted position. Is an operating force urging portion that is disposed on the side opposite to the thermal head with respect to the transport roller and that urges an operating force, and is disposed on the thermal head side with respect to the transport roller, and includes the thermal head. An operating unit that operates to move between the printing position and the retreat position; and the operating force applied by the operating force applying unit to the operating unit. And a transmitting unit that transmits, the transmission unit, thermal printer, characterized in that in passing between the substrate and the conveying rollers are arranged.