Guide roller with magnet and bushing for stabilizing roller

Abstract

The invention provides a belt guide roller and a belt driver, and the belt guide roller is provided with a magnet and a bushing so as to stabilize a roller for a belt medium. The belt guide roller has a roller body extending about a vertical axis. The tape medium passes through the roller barrel to guide the tape medium on a tape path. A plurality of magnets positioned relative to the vertical axis provide an axial force to axially stabilize the tape guide roller.

Description

Background Art 1. Field of the Invention

[0001] The present invention provides a tape guide roller and a tape drive, wherein the tape guide roller has a magnet and a bushing to stabilize a roller for a tape medium.

[0002] 2. Description of Related Technology

[0003] In a magnetic storage system, data is read from and written to a magnetic recording medium using magnetic read and write elements formed on a tape head. Data is written to a magnetic recording medium by moving a magnetic recording transducer to the location on the medium where the data is to be stored. The magnetic recording transducer generates a magnetic field that encodes the data into the magnetic medium. Data is read from the medium by similarly positioning the magnetic read element and then sensing the magnetic field of the magnetic medium. The read and write operations can be independently synchronized with the movement of the medium to ensure that data can be read from and written to the desired location on the medium.

[0004] The tape drive includes a tape guide roller positioned relative to the read / write tape head in order to guide and position the tape media as it passes the read / write tape head. The tape guide roller includes a ball bearing in a roller over which the tape media passes. The tape guide roller is one of the main contributors to mechanical disturbances in a tape drive, increasing the standard deviation of the position error signal (PES), which results in more read and write errors of the tape head. One technique to reduce the mechanical disturbance introduced by the tape guide roller is to use air bearing rollers, which require pressurized air to function.

[0005] In the tape path for servo formatting, i.e., writing the servo pattern onto the tape during tape manufacturing, there is a further need for tape guide rollers with low mechanical disturbances. Mechanical disturbances caused by the tape guide rollers during servo formatting result in disturbances in the servo pattern written to the tape media / tape cartridge, which further degrades the standard deviation of the position error signal (PES) during read and write operations in the tape drive.

[0006] There is a need in the art for improved techniques to implement belt guide rollers to reduce mechanical interference in belt drives. Summary of the invention

[0007] The present invention provides a tape guide roller and a tape drive, the tape guide roller having magnets and bushings to stabilize a roller for tape media. The tape guide roller has a roller body extending about a vertical axis. The tape media passes through the roller to guide the tape media on a tape path. A plurality of magnets positioned relative to the vertical axis provide an axial force to axially stabilize the tape guide roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 An embodiment of a belt drive system in which an embodiment is implemented is shown.

[0009] Figure 2 An embodiment of a cutaway view of a tape drive housing is shown to illustrate internal components of the tape drive.

[0010] Figure 3 An embodiment is shown in a side view with guide rollers.

[0011] Figure 4 Show Figure 3 Embodiment of a cross-sectional view of a belt guide roller.

[0012] Figure 5 A cross-sectional view of an embodiment with guide rollers is shown.

[0013] Figure 6 Show Figure 5 Embodiment of the roller body with guide roller.

[0014] Figure 7 Show Figure 5 Perspective view of the belt guide rollers.

[0015] Figure 8 Show Figure 5 A front view of an embodiment of a belt guide roller.

[0016] Fig. 9 , 10 11 show embodiments of the location of magnets, bushings and thrust bearings in the belt guide rollers.

[0017] Fig.12 An embodiment of a thrust bearing is shown. DETAILED DESCRIPTION

[0018] Tape cartridge capacity gains require improved track density scaling to read the increasingly denser tracks. A key enabler for track density scaling is to improve the track following performance of the tape drive, i.e., to reduce the standard deviation of the position error signal (sigma PES) when reading and writing data during track following. Track following performance can be limited by mechanical disturbances in the tape drive. One of the main contributors to these disturbances is the tape guide rollers, which typically use ball bearings and generate disturbances over a wide frequency range. These disturbances shift to higher frequencies as tape speed increases, making it more challenging to achieve low sigma PES at high tape speeds. The disturbances caused by the tape roller guides also vary significantly from roller to roller, most likely due to variations in the bearings themselves and in the assembly process.

[0019] The described embodiments provide improved techniques for components for belt guide rollers in which passive magnetic bearings are deployed to provide axial stability of the rollers, the rollers being combined with bushings for the shafts that extend through the rollers to provide radial stability. Additional embodiments may utilize thrust bearings positioned at the bottom of the shafts that extend through the rollers. It has been found that some combinations of components utilizing magnets, bushings, and thrust bearings provide improved track following performance and lower sigma PES than that achieved with ball bearing rollers. Further, it has been found that the use of magnets, bushings, and / or thrust bearings provides comparable track following performance to belt guide rollers utilizing air bearing rollers, which are much more expensive to manufacture than the described embodiments of magnetic bearings, bushings, and / or thrust bearings.

[0020] In one embodiment, the belt guide roller is implemented with a passive magnetic bearing (PMB) in combination with a thrust bearing. In another embodiment, the belt guide roller is implemented with a passive magnetic bearing and a thrust bearing in combination with a bushing, and the passive magnetic bearing may include synthetic sapphire / ruby / corundum. An embodiment provides track following performance that is an improvement over existing ball bearing rollers and has a performance profile comparable to that achieved with air bearing belt guides. However, the described embodiments can be manufactured at a much lower cost than air bearing rollers.

[0021] Figure 1 An embodiment of a tape drive 100 for reading and writing relative to a magnetic tape 102 of a tape cartridge 104 is shown. The tape cartridge 104 includes a length of magnetic tape 102 wound on one or two reels 106, 108. As an example, the tape cartridge 102 may include a single reel of tape, for example, following a linear tape open (LTO) format. An example of the tape drive 100 is an International Business Machines Corporation TS1160 tape drive. Other implementations of the tape cartridge 102 and tape drive may also be used, such as an LTO-type tape drive.

[0022] The tape drive 100 may also include one or more controllers 110 to operate the tape drive 100 according to commands received at the interface 114 from the host system 112. The controller 110 includes logic and / or one or more microprocessors with memory for storing information and program information for operating the microprocessor(s). The tape drive 100 may include a stand-alone unit or may include part of a tape library or other subsystem. The tape drive 100 may be coupled to the host system 112 directly, through a library, or through a network, and may employ a small computer system interface (SCSI), a fiber channel interface, or the like at the interface 14.

[0023] The tape cartridge 104 may be inserted into the tape drive 100 and loaded by the mechanism of the tape drive 100 so that as the tape is longitudinally moved by one or more motors 120 rotating the reels 106, 108, one or more read and / or write elements on the tape head 118 read and / or write information in the form of signals relative to the tape 104. The tape guide rollers 130 guide the tape 104 across the tape head 118 to stabilize the positioning of the tape 104 relative to the tape head 118, thereby reducing position error signals (PES). The tape typically includes a plurality of parallel tracks or groups of tracks. In some formats, such as the LTO format described above, the tracks are arranged in a separate, wound, serpentine reciprocating pattern, as known to those skilled in the art.

[0024] The recording system may include a servo control system 122 to electronically switch to another set of read and / or write elements on the tape head 118, and / or to seek and move the tape head 118 laterally on the tape 102, position the read and write elements at the desired one or more turns, and track the desired one or more turns. The servo control system 122 may also control the operation of the motor 120 through the motor driver 124 and in response to instructions from the controller 110.

[0025] The controller 110 also employs a buffer 126 and a recording channel 128 to provide a data stream and formatter for reading data from and writing data to the tape. The controller 110 may include program code in a memory device that is loaded into a processor and executed to perform tape drive operations. Alternatively, some or all of the functions of the controller 110 may be implemented as microcode or firmware in a hardware device in the tape drive 100, such as an application specific integrated circuit (ASIC). The buffer 126 may include a suitable volatile or non-volatile memory device known in the art.

[0026] Figure 2 An embodiment of a tape drive 200 is shown showing internal components within a cut-away portion 201 of a tape drive housing 202. The tape drive 200 includes the housing 202, a tape cartridge 204 inserted into an opening 206 of the tape drive 200. The tape cartridge includes a supply reel 208 having a tape media accessed by a take-up reel 210 that feeds a tape media 212 via tape guide rollers 214a, 214b, 214c, 214d to guide the tape 212 via a tape head 216 for reading and writing relative to the tape media 212.

[0027] Figure 3 An embodiment with guide rollers 300 is shown, for example Figure 2 The guide rollers 214a, 214b, 214c, 214d and Figure 1130, the tape guide roller 300 has a housing 301 including an axle 302 or shaft extending along a vertical axis extending through the center of a roller 304. The housing 301 is formed to expose the entire surface of the roller 304 over which the tape media passes. The roller 304 forms a grooved surface 306 over which the tape media 212 passes. The grooved surface 306 improves traction between the tape media 212 and the roller 304. The grooves 306 may include ridges forming a spiral across the roller 304 or may be parallel.

[0028] Figure 4 Shows Figure 3 The belt guide roller 300 along Figure 3 In the cross-sectional view of the vertical section 310 in FIG. 3 , there are two pairs of opposing magnets inside the roller 304, namely, upper annular magnets 312a, 314a and two opposing lower annular magnets 312b, 314b. There are open spaces 320a, 320b between each pair of magnets 312a, 314a and 312b, 314b, respectively. Each pair of opposing magnets 312a, 314a and 312b, 314b may have opposite polarities. In an alternative embodiment, each pair of magnets 312a, 314a and 312b, 314b may form concentric rings. The annular magnets 312a, 314a and 312b, 314b may include axial radial passive magnetic bearings. The magnets 312a, 312b, 314a, 314b provide axial stability of the shaft 302 and the roller 304 to reduce the position error signal (PES).

[0029] Each pair of opposing magnets includes an outer magnet 312a, 312b and an inner magnet 314a, 314b. The outer magnets 312a, 312b are mounted to outer support structures 316a, 316b, respectively. The inner magnets 314a, 314b are mounted to inner support structures 317a, 317b, respectively. The inner support structures 317a, 317b are attached to the shaft 302 and the roller 304 and couple the shaft 302 to the roller 304. When the shaft 302, to which the roller 304 is fixed, rotates, the roller 304 rotates. The shaft rotation causes the inner magnets 314a, 314b to rotate.

[0030] The outer magnets 312a, 312b are fixed to the outer support structures 316a, 316b and may not rotate relative to the shaft 302 and the roller 304. When the shaft 302 rotates, the inner magnets 314a, 314b rotate relative to the outer magnets 312a, 312b, respectively. The outer magnets 312a, 312b may not rotate because they are fixed to the outer support structures 316a, 316b, respectively, which are not connected to the shaft 302.

[0031] The upper end of the shaft 302 extends through the upper bushing 318a and is supported by the upper bushing support 319. The bottom bushing 318b can be fixed to the structure. Both bushings 318A, 318B can be non-rotating and include synthetic sapphire, synthetic ruby, corundum or other materials with high hardness, low friction and wear, and a very smooth surface produced by polishing. Lubricant can be applied between the shaft 302 and the bushings 318A, 318b.

[0032] Figure 5 A cross-sectional view of another embodiment of a guide roller 500 is provided having a housing 501, an interior space 502 for a shaft (not shown), a roller 504, an upper bushing 506a and a lower bushing 506b through which the shaft extends through the interior space 502. There are also opposing pairs of upper rings 510a, 510b and opposing pairs of lower rings 512a, 512b passive magnetic bearings. Figure 5 , the upper magnets 510a, 510b are positioned above the upper end of the roller 504 relative to the vertical axis, and the lower magnets 512a, 512b are positioned below the lower end of the roller 504. Each pair of opposing magnets includes an outer magnet 510a, 512b and an inner magnet 510b, 512a. The outer magnets 510a, 512b are fixed to the roller frame / external support structure (located above and below the outer magnets 510a, 512b, respectively) and cannot rotate relative to the axis set in the internal space 502 and the roller 504. The inner magnets 510b, 512a are attached to the shaft (not shown) in the internal space 502 and the roller 504. When the shaft in the internal space 502 and the roller 504 rotates, the internal magnets 510b, 512a rotate relative to the outer magnets 510a, 512b, respectively. The labeled distances between the components in the figure are in millimeters (mm).

[0033] Figure 6 An embodiment of the grooves in the roller 504 is shown having spaced ridges which may be parallel or in a spiral form. The enlarged view 520 shows the ridges 522 forming the grooves in the roller 504. In one embodiment, the grooves 522 are spaced apart at a distance of 0.05 mm and the roller 500 has a diameter of 20 mm, wherein the distances in the figure are in millimeters (mm).

[0034] Figure 7 Provided Figure 5 601 is a perspective view of the guide roller 500, wherein the housing 601 is shown as transparent, with an opening 603 exposing the roller 604, the upper bushing 606, and the passive magnetic bearings of the upper rings 610a, 610b and the lower rings 612a, 612b. The opening 603 of the housing 601 exposes the extended surface of the roller 604 to engage the belt media channel.

[0035] Figure 8 Show Figure 5 , 6 7 and a front view of the guide roller 600, showing the housing 601, the roller 604, the two upper magnets 610a, 610b, the two lower magnets 612a, 612b, the end of the shaft 602, and the opening 603 in the housing 601, which exposes the surface of the roller 604 to engage the belt media.

[0036] Fig. 9 An embodiment of the positioning of magnets within the belt guide roller 900 relative to the shaft 902 is shown. There are two upper magnets 904a, 904b of opposite polarity and two lower magnets 906a, 906b of opposite polarity and bushings 908a, 908b, for example, in Figure 3 , 4 , 5, 7 and 8.

[0037] Fig.10 An alternative embodiment of placing magnets within the guide roller 1000 relative to the shaft 1002 is shown. There is a set of magnets 1004a, 1004b of opposite polarity at the upper end of the belt guide roller 1000. Bushings 1008a and 1008b radially stabilize the shaft 1002. A thrust bearing 1010 may be located below the lower end of the shaft 1002 to further stabilize the shaft 1002. The thrust bearing 1010, which is composed of a hemisphere / ball and a surrounding flat surface, may include the same material as the bushings 1008a, 1008b, such as synthetic sapphire / ruby or corundum, or may be composed of a steel ball or tip on a brass or steel plate, or may be composed of a steel shaft and a polished plate on a steel, (synthetic) sapphire, ruby ​​or corundum ball or hemisphere to engage the bottom end of the shaft 1002. The thrust bearing may be lubricated or unlubricated. In another embodiment, there may be two pairs of axial magnets, for example, such as Fig. 9 The passive magnetic bearing shown in FIG. 1002 has a thrust bearing located at the bottom end of the shaft 1002. Fig.10 As shown, the thrust bearing 1010 provides axial stability for the shaft 1002 .

[0038] Additional embodiments may vary the arrangement and number of magnets and the polarity of the arranged magnets, and may optionally include a thrust bearing at the upper end of the shaft. Fig.11 An alternative magnet and thrust bearing configuration is shown for a guide roller 1100 having a shaft 1102 and an axial radial passive bearing magnet comprising a stack of concentric ring magnetic elements including five inner PBM magnetic rings 1104 and four outer PBM magnetic rings 1106, and a thrust bearing 1108. Magnets 1104 and 1106 have the same polarity.

[0039] Fig.12An embodiment of a thrust bearing 1200 is shown that includes an inner ball 1202 composed of a material such as synthetic sapphire, synthetic ruby, or corundum. The shaft end may contact the ball portion 1202 of the thrust bearing 1200 and fit through an opening of a bushing 1204 of the thrust bearing 1200.

[0040] It has been discovered that the above-described embodiments employing magnets, bushings, and thrust bearings significantly reduce position error signal (PES) read / write detection during tape operation by providing axial and radial stability.

[0041] In the above described embodiments, magnets and bushings are used. In alternative embodiments, magnets or bushings may be used alone to provide stability to reduce position error signals.

[0042] The present invention may be a guide roller, a belt drive, and a method for implementing a guide roller. A system, method, and / or computer program product implemented in the controller 110.

[0043] In the described embodiments, the variables i, n, etc., when used with different elements, may represent the same or different instances of that element.

[0044] The terms “embodiment,” “embodiments,” “the embodiment,” “these embodiments,” “one or more embodiments,” “some embodiments,” and “one embodiment” mean “one or more (but not all) embodiments of the invention,” unless expressly stated otherwise.

[0045] The terms "including", "comprising", "having" and variations thereof mean "including but not limited to", unless expressly stated otherwise.

[0046] Unless expressly stated otherwise, the enumerated listing of items does not imply that any or all of the items are mutually exclusive.

[0047] The terms "a", "an" and "the" mean "one or more" unless expressly stated otherwise.

[0048] Unless expressly stated otherwise, devices that are in communication with each other need not be in continuous communication with each other. In addition, devices that are in communication with each other may communicate directly or indirectly through one or more intermediaries.

[0049] The description of an embodiment with several components in communication with each other does not imply that all such components are required. Rather, various optional components are described to illustrate various possible embodiments of the invention.

[0050] When a single device or product is described herein, it will be apparent that more than one device / product (whether or not they collaborate) may be used in place of a single device / product. Similarly, where more than one device or product (whether or not they collaborate) is described herein, it will be readily apparent that a single device / product may be used in place of more than one device or product, or that a different number of devices / products may be used in place of the number of devices or programs shown. The functions and / or features of a device may alternatively be embodied by one or more other devices that are not explicitly described as having such functions / features. Therefore, other embodiments of the present invention need not include the device itself.

[0051] For the purpose of illustration and description, the above description of various embodiments of the present invention has been given. It is not exhaustive, nor is it intended to limit the present invention to the precise form disclosed. In accordance with the above teachings, many modifications and variations are possible. The scope of the present invention is not limited by this detailed description, but by the appended claims. The above description, examples and data provide a complete description of the manufacture and use of the composition of the present invention. Since many embodiments of the present invention can be made without departing from the spirit and scope of the present invention, the present invention lies in the appended claims.

Claims

1. A tape guide roller for guiding a tape medium relative to a read or write head for reading or writing relative to the tape medium, the tape guide roller comprising: a roller extending about a vertical axis, wherein the tape media passes through the roller to guide the tape media on a tape path; as well as A plurality of magnets are positioned relative to the vertical axis to provide an axial force to axially stabilize the belt guide roller.

2. The tape guide roller of claim 1, wherein the magnets comprise at least one pair of opposing rings of passive magnetic bearings extending about the vertical axis and having opposite polarities, the tape guide roller further comprising: A shaft extends through the roller, wherein the rings of each pair of passive magnetic bearings are separated by a distance on the vertical axis.

3. The belt guide roller of claim 1, wherein the roller has an upper end and a lower end relative to the vertical axis, wherein the magnet comprises: a first pair of magnets positioned along the vertical axis closer to the upper end than the lower end of the roller; as well as A second pair of magnets is positioned along the vertical axis closer to the lower end of the roller than the upper end.

4. The belt guide roller of claim 3, wherein the first pair of magnets are positioned above the upper end of the roller on the vertical axis, and wherein the second pair of magnets are positioned below the lower end of the roller on the vertical axis.

5. The belt guide roller according to claim 3, further comprising: a shaft extending along the vertical axis through the roller and the first and second pairs of magnets, wherein the shaft has an upper end and a lower end relative to the vertical axis; a first bushing positioned above the first pair of magnets on the vertical axis, wherein the shaft extends through the first bushing; and A second bushing is positioned below the second pair of magnets on the vertical axis, wherein the shaft extends through the second bushing, wherein the first bushing and the second bushing radially stabilize the belt guide roller.

6. The belt guide roller of claim 5, wherein the first bushing and the second bushing are constructed of one of a group of materials, the group of materials comprising: Synthetic sapphire, synthetic ruby, and corundum.

7. The belt guide roller according to claim 1, further comprising: a shaft extending through the roller along the vertical axis; a first internal support structure coupled to the shaft and the roller; a first internal magnet coupled to the first internal support structure; a first external support structure; a first external magnet coupled to the first external support structure; a second internal support structure coupled to the shaft and the roller; a second internal magnet coupled to the second internal support structure; a second external support structure; as well as A second external magnet is coupled to the second external support structure, wherein the first and second internal support structures are between the first and second external support structures along the vertical axis.

8. The tape guide roller of claim 1 , wherein the roller has an upper end and a lower end relative to the vertical axis, wherein the magnet is positioned closer to the upper end of the roller than the lower end of the roller, the tape guide roller further comprising: a shaft extending through the roller and the magnet along the vertical axis, wherein the shaft has an upper end and a lower end relative to the vertical axis; and A thrust bearing is positioned below and in contact with the lower end of the shaft on the vertical axis.

9. The belt guide roller according to claim 8, further comprising: a first bushing positioned above the magnet along the vertical axis, wherein the shaft extends through the first bushing; as well as A second bushing is positioned along the vertical axis between the magnet and the thrust bearing.

10. A tape drive for performing a read or write operation on a tape medium, comprising: a read or write head for reading or writing relative to the tape medium; A tape guide roller for guiding the tape media relative to the read or write head, comprising: a roller extending about a vertical axis, wherein the tape media passes through the roller to guide the tape media on a tape path; as well as A plurality of magnets are positioned relative to the vertical axis to provide an axial force to axially stabilize the belt guide roller.

11. The belt drive of claim 10, wherein the magnets comprise at least one pair of opposing rings of passive magnetic bearings extending about the vertical axis and having opposite polarities, wherein the belt guide rollers further comprise: A shaft extends through the roller, wherein the rings of each pair of passive magnetic bearings are separated by a distance on the vertical axis.

12. The belt drive of claim 10, wherein the roller has an upper end and a lower end relative to the vertical axis, wherein the magnet comprises: a first pair of magnets positioned along the vertical axis closer to the upper end than the lower end of the roller; as well as A second pair of magnets is positioned along the vertical axis closer to the lower end of the roller than the upper end.

13. The belt drive of claim 12, wherein the belt guide roller further comprises: a shaft extending along the vertical axis through the roller and the first and second pairs of magnets, wherein the shaft has an upper end and a lower end relative to the vertical axis; a first bushing positioned above the first pair of magnets on the vertical axis, wherein the shaft extends through the first bushing; and A second bushing is positioned below the second pair of magnets on the vertical axis, wherein the shaft extends through the second bushing, wherein the first bushing and the second bushing radially stabilize the belt guide roller.

14. The belt drive of claim 13, wherein the first bushing and the second bushing are constructed of one of a group of materials, the group of materials consisting of: Synthetic sapphire, synthetic ruby, and corundum.

15. The belt drive of claim 10, wherein the belt guide roller further comprises: a shaft extending through the roller along the vertical axis; a first internal support structure coupled to the shaft and the roller; a first internal magnet coupled to the first internal support structure; a first external support structure; a first external magnet coupled to the first external support structure; a second internal support structure coupled to the shaft and the roller; a second internal magnet coupled to the second internal support structure; a second external support structure; as well as A second external magnet is coupled to the second external support structure, wherein the first and second internal support structures are between the first and second external support structures along the vertical axis.

16. The belt drive of claim 10, wherein the roller has an upper end and a lower end relative to the vertical axis, wherein the magnet is positioned closer to the upper end of the roller than the lower end of the roller, wherein the belt guide roller further comprises: a shaft extending through the roller and the magnet along the vertical axis, wherein the shaft has an upper end and a lower end relative to the vertical axis; and A thrust bearing is positioned below and in contact with the lower end of the shaft on the vertical axis.

17. A tape guide roller for guiding a tape medium relative to a read or write head for reading or writing relative to the tape medium, the tape guide roller comprising: The housing comprises: a roller extending about a vertical axis, wherein the tape media passes through the roller to guide the tape media on a tape path; and a plurality of magnets positioned relative to the vertical axis to provide an axial force to axially stabilize the belt guide roller; and An opening is located in the housing to expose a surface of the roller to engage the belt media.

18. The tape guide roller of claim 17, wherein the magnets comprise at least one pair of opposing rings of passive magnetic bearings extending about the vertical axis and having opposite polarities, the tape guide roller further comprising: A shaft extends through the roller, wherein the rings of each pair of passive magnetic bearings are separated by a distance on the vertical axis.

19. The belt guide roller of claim 17, wherein the roller has an upper end and a lower end relative to the vertical axis, wherein the magnet comprises: a first pair of magnets positioned along the vertical axis closer to the upper end than the lower end of the roller; as well as A second pair of magnets is positioned along the vertical axis closer to the lower end of the roller than the upper end.

20. The belt guide roller of claim 19, further comprising: a shaft extending along the vertical axis through the roller and the first and second pairs of magnets, wherein the shaft has an upper end and a lower end relative to the vertical axis; a first bushing positioned above the first pair of magnets on the vertical axis, wherein the shaft extends through the first bushing; and A second bushing is positioned below the second pair of magnets on the vertical axis, wherein the shaft extends through the second bushing, wherein the first bushing and the second bushing radially stabilize the belt guide roller.

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