Abstract:
For a motor having liquid lubricated bearing surface(s), aspects include providing a column shaped Capillary Seal (CS) for storing and supply lubricating liquid to the bearing surface(s). The column shaped CS may have a cross-section substantially topologically equivalent to a circle. Aspects include disposing the column shaped CS between relatively rotational motor members or between relatively irrotational motor members. Other aspects include disposition of the column shaped CS in a spiral shape where one opening of the CS fluidicly communicates with the bearing surface and another opening vents to a gas environment. Still other aspects include disposing the column shaped CS circumferentially on surfaces of generally cylindrical shaped motor members. Such surfaces may oppose a second surface that is one of relatively rotational and relatively irrotational vis the surface. The column shaped CS may circumscribe an axis of a rotating member or may be disposed parallel to the axis of the rotating member.

Description:
BACKGROUND 
     1. Field 
     The present invention relates generally to seals for Fluid Dynamic Bearing (FDB) motors and more particularly to capillary seals and lubricating liquid reserviors for use in FDB motors. 
     2. Description of Related Art 
     Capillary seals are presently used to retain lubricating liquid (e.g., oil) at hydrodynamic bearing surfaces of disc drive motors and to provide a reservoir of lubricating liquid sufficient to maintain lubrication of hydrodynamic bearing surfaces throughout an expected lifetime of the disc drive. 
     Typical capillary seals are formed between radially opposing surfaces of coaxially disposed relatively rotating members of a disc drive motor, e.g., between an outer surface of a fixed shaft and an inner surface of a rotating hub disposed around the shaft. Typically, either the shaft or the hub is machined so that the radially opposing surfaces taper with respect to each other and thereby form a capillary seal with an annular type cross-section that tapers in cross-sectional area from a vent opening to the hydrodynamic bearing. 
     Such capillary seals often have a relatively large cross-sectional area exposed to an ambient environment, and thus may be prone to losing fluid due to operational shock and/or evaporation. Accordingly, capillary seals and reservoirs using capillary forces that may have benefits including a reduction in a cross-sectional area exposed to an ambient environment and an increase in shock resistance of the seals and reservoirs are desired. 
     SUMMARY 
     In an aspect, a capillary seal comprises a structure having formed therein a column shaped first channel. The first channel has a first opening, a second opening, and a cross-section. The cross-section of the first channel at the first opening may have an area greater than an area of the cross-section of the first channel at the second opening. The first channel is formed for fluidic communication with a hydrodynamic bearing through the second opening and to a gaseous environment through the first opening. Lubricating liquid is disposed in the first channel. 
     Channels of column shaped seals may be disposed as spiral shapes, straight shapes, and other shapes on a surface. Multiple channels may be disposed as circumferential spiral shapes on generally cylindrical, spherical or conical surfaces, as co-axial spiral shapes on generally planar surfaces, as curved channels radiating from a central portion, as straight channels radiating from a central portion, as straight channels co-parallel and dispersed on a radial surface, and in a variety of other dispositions. Channel cross-sections according to various aspects described herein may be substantially topologically equivalent to circles, and may be like various shapes, including semi-circles, triangles, trapezoids, and rectangles. 
     Other aspects include motors using such capillary seal aspects as a means for storing and supplying lubricating liquid to a hydrodynamic bearing that supports relative rotation between a first motor member and a second motor member coaxially disposed about the first motor member. Such capillary seals may be disposed between relatively rotating motor members and between relatively stationary members. Capillary seals disposed between relatively stationary members may rotate with rotating members or be stationary with stationary members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of aspects and examples disclosed herein, reference is made to the accompanying drawings in the following description. 
         FIG. 1  illustrates a plan view of an exemplary disc drive; 
         FIG. 2   a  illustrates a prior art capillary seal in the context of a vertical cross-section of a motor portion; 
         FIG. 2   b  illustrates a cross-section of prior art capillary seal; 
         FIG. 3  illustrates a vertical cross-section of a portion of an exemplary disc drive motor; 
         FIG. 4   a  illustrates a perspective view of an exemplary column capillary seal that may be used in the disc drive motor of  FIG. 3 ; 
         FIG. 4   b  illustrates an exemplary column capillary seal that may be used in the disc drive motor of  FIG. 3 ; 
         FIG. 5   a - c  illustrate exemplary cross-sections of exemplary column capillary seals; 
         FIG. 6  illustrates another exemplary disc drive motor in which aspects of exemplary capillary seals may be used; 
         FIG. 7   a  illustrates an exemplary column capillary seal that may be used in the exemplary disc drive motor of  FIG. 6 ; 
         FIG. 7   b  illustrates another exemplary column capillary seal that may be used in the exemplary disc drive motor of  FIG. 6 ; 
         FIG. 8  illustrates a cross-section of a third exemplary disc drive motor wherein aspects of exemplary column capillary seals may be used; 
         FIG. 9  illustrates a cross-section of a fourth exemplary disc drive motor portion; 
         FIG. 10  illustrates a perspective view of a disc drive motor member having an exemplary column capillary seal that may be used in the disc drive motor portion of  FIG. 9 ; and 
         FIG. 11  illustrates a perspective view of an exemplary top surface of the member of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable a person of ordinary skill in the art to make and use various aspects of the inventions. Descriptions of specific materials, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the inventions. For example, aspects and examples may be employed in a variety of motors, including motors for use in disc storage drives. Motors for disc storage drives may be designed and may operate in a number of ways. The exemplary motors and other exemplary subject matter provided herein are for illustrating various aspects and are not intended to limit the range of motors and devices in which such examples and aspects may be applied. 
     Turning briefly to  FIG. 1 , a plan view of an exemplary magnetic disc drive storage system is illustrated. In this example, the storage system  10  includes a housing base  12  having spindle motor  14  which rotatably carries storage discs  16 . An armature assembly  18  moves transducers  20  across the surface of the discs  16 . The environment in which discs  16  rotate may be sealed by seal  22  and cover  24 . In operation, discs  16  rotate at high speed while transducers  20  are positioned at any one of a radially differentiated track on the surface of the discs  16 . This allows transducers  20  to read and write magnetically encoded information on the surfaces of discs  16  at selected locations. Discs  16  may rotate at many thousand RPM. 
     To provide for rotation of discs  16 , spindle motor  14  typically includes at least one rotatable portion. The at least one rotatable portion in turn typically interfaces with one or more non-rotating surfaces, that may form journal and/or thrust hydrodynamic bearings. Hydrodynamic bearings often incorporate liquid lubricants, such as oil between the rotatable portion(s) and fixed portion(s) of spindle motor  14 . Capillary seals help confine liquid lubricant to areas intended for lubrication and also provide a reservoir of liquid lubricant that compensates for losses due to evaporation, spillage and the like. 
       FIG. 2   a  illustrates a vertical cross-section of a portion of an exemplary motor  14  having a prior art capillary seal  210 . This motor includes a shaft  205 , a sealing cone  225  and a rotatable hub  215 . The sealing cone  225  has an outer surface that radially opposes an inner surface of rotatable hub  215 . The outer surface of sealing cone  225  and the inner surface of the rotatable hub  215  taper with respect to each other, thereby forming a capillary seal portion  210  that has a cross-section which tapers in area from a vent opening  245  towards an opening in fluidic communication with a hydrodynamic bearing surface  220 . Capillary seal  210  is partially filled with a lubricating liquid that forms a meniscus. 
     A characterization of prior art capillary seals, such as capillary seal  210  may be obtained through topology. In topological theory, a geometric figure, such as a surface in two or three dimensions, may be characterized by its topographic equivalency to other geometric figures. Generally, a first geometric figure is equivalent to a second geometric figure if the first can be transformed into the second by transformations such as bending, stretching, twisting, and the like. However, if transformations such as tearing or cutting are required to transform the first into the second then the first and the second figures are not equivalent. For instance, a square surface may hypothetically be transformed into an equivalent circular surface by bending the edges of the square surface into a circular shape. Yet that square surface could not be transformed into an annular surface without cutting a portion of the surface of the square. Thus, a square surface is not topologically equivalent to an annular surface. 
     Viewed in horizontal cross-section, capillary seal  210  of  FIG. 2   a/b  has a cross-section topologically equivalent to an annulus (e.g., a ring). The annulus has an inner boundary and an outer boundary, where the inner boundary of the annular cross-section is formed by the outer surface of sealing cone  225  and the outer boundary of the annular cross section is formed by the inner surface of rotatable hub  215 . 
     As illustrated in  FIG. 2   b , a difference between a radius of the inner boundary and a radius of the outer boundary of the annular cross-section is relatively small. A schematic view of capillary seal  210 , with hub  215  and sealing cone  225  demarcated in  FIG. 2   b  conceptually illustrates that prior art capillary seals typically have annular cross-sections, where the differences in radii of inner and outer boundaries of each cross-section is relatively small. Such considerations may also be viewed qualitatively, as described herein. 
     As a motor ages, lubricating liquid may be lost through evaporation or escape of the lubricating liquid from the capillary seal(s). Thus, a typical capillary seal is designed to provide a volume of lubricating liquid to compensate for that loss of lubricating liquid. As illustrated in  FIG. 2   a , providing a reservoir of lubricating liquid in the capillary seal imposes design difficulties because a longer capillary seal of the type in  FIG. 2   a/b  is more difficult to fit within a motor and generally requires alterations in the design of various motor members. However, a wider capillary seal, which has a higher volume for a seal of a given length and taper angle, is typically less resistant to spillage under shock and presents a larger surface area to an ambient environment, which would result in more evaporation of lubricating liquid from the seal. For example, the prior art capillary seal of  FIG. 2   a/b  has a relatively high width to length ratio. 
     Now turning to  FIG. 3 , a cross-section of a portion of an exemplary motor  300  having a capillary seal aspect is illustrated. The exemplary motor  300  includes a shaft  305 , and a co-axially disposed hub  310  coupled with shaft  305 . A sleeve  315  and shaft  305  interface to form hydrodynamic bearing regions  320 , which support rotation of shaft  305  and hub  310  about sleeve  315 . Sleeve  315  includes an outer surface  325  that interfaces with cup  323  to form a recirculation channel  330 . A limiter  340  extends from hub  310  and interfaces with cup  323  to form an annular opening  345 , at which a secondary meniscus of lubricating liquid forms. 
     The secondary meniscus aids in retaining lubricating liquid within motor  300 , and advantageously has a small area exposed to an ambient environment  380  compared with many menisci of prior art capillary seals. Magnet  385  couples with limiter  340  to face a stator  390  that electromagnetically interacts with magnet  385  for rotating hub  310  and shaft  305 . Motors according to exemplary aspects described herein may have additional secondary menisci formed at other openings by lubricating liquid. One of ordinary skill in the art would understand that exemplary aspects herein more generally illustrate that separate menisci may be used for retaining lubricating liquid in a reservoir and for reducing escape of lubricating liquid from openings at one or more parts of a motor. 
     Cup  323  supports sleeve  315 . Cup  323  is in turn supported by a seal cover  350  that shields a column shaped capillary seal  355  (a disposition of which is generally illustrated by dashed lines) formed in base  360  from ambient environment  380 . Capillary seal  355  has two openings: a bearing opening  365  and a vent opening  370 . Bearing opening  365  provides fluidic communication of capillary seal  355  with hydrodynamic bearing regions  320 . Vent opening  370  vents capillary seal  355  with ambient environment  380 , which may contain air or another gas or mixture of gases. As illustrated, capillary seal  355  is disposed between two parts (cover  350  and base  360 ) that are not disposed for relative rotation with respect to each other. Moreover, capillary seal  355  is disposed between two surfaces other than the surfaces (surfaces of sleeve  315  and shaft  305 ) forming hydrodynamic bearing regions  320  (i.e., capillary seal  355  is not for example formed between sleeve  315  and shaft  305 ). 
     Other arrangements and configurations of the before mentioned parts are possible. For instance, cup  323  and sleeve  315  may be formed unitarily and recirculation channel  330  may be formed by removing material. Alternatively, recirculation channel  330  may be omitted. Magnet  385  may be coupled with limiter  340  by any number of methods known in the art. All the above mentioned components may have different absolute and/or relative (with respect to other parts) dimensions. For instance, hub  310  may have a bigger radius, limiter  340  may be shorter or longer, cup  323  may be thinner or thicker, and the like. Other capillary seal aspects will be illustrated in still other motor configurations and arrangements. Those of skill in the art would understand that some aspects illustrated with respect to other figures may be used in exemplary motor  300 . 
     Turning now to  FIGS. 4   a  and  4   b , further explication of exemplary column shaped capillary seal  355  is provided. Exemplary capillary seal  355  contains two distinct column shaped capillary seals ( 355   a  and  355   b ), capillary seals  355   a  and  355   b  include a respective channel defined by a generally planar surface of base  360 , vent openings  370   a  and  370   b  and bearing openings  365   a  and  365   b  (at center, general location illustrated in cross section of  FIG. 3 ). As illustrated, the channels of capillary seals  355   a    355   b  are disposed as co-axial planar spiral shapes with vent opening  370   a  opposite vent opening  370   b . The spiral shapes converge on a central portion  405 . Bearing openings  365   a  and  365   b  (indicated in cross section in  FIG. 3 ) may also be formed for a disposition that provides for bearing openings  365   a  and  365   b  to be on opposite sides of shaft  305  ( FIG. 3 ). Thus, capillary seal  355  includes a structure having defined therein one or more channels, each channel with at least two openings, one of the openings for providing lubricating liquid to hydrodynamic bearing regions, and the other opening for venting the channel to an ambient environment. 
     Although  FIG. 4   a  illustrates capillary seal  355  as including two separate spiral shaped capillary seals  355   a  and  355   b  (each having a distinct channel), capillary seal  355  may be comprised of fewer or more separate capillary seals that may be disposed as co-axial spirals, or other shapes that provide for a column shaped capillary seal (i.e., a spiral is a convenient, but not a sole disposition for a column shaped capillary seal). Capillary seals  355   a  and  355   b  may be formed by removing material from the surface of base  360 , by adding material to base  360 , such as by attaching a spiral shape to the surface of base  360 , or by other methods of formation such as stamping, which displaces material from one portion of base  360  to another portion of base  360 . Cover  350  may be altered to accommodate such differences where desirable. Additionally, capillary seals  355   a  and  355   b  could be formed in part or whole by adding material to or removing material from cover  350 . For instance, a spiral shaped channel may be formed in cover  350  and another may be formed in base  360 . The spiral channels may be aligned to result in one capillary seal, or may be aligned such that lands (portions of base  360  higher than a bottom portion of the spiral channel) of one opposing surface provide a “cover” for the channel(s) on the other opposing surface. 
     Exemplary column capillary seals may also be defined by using a thin layer disposed between base  360  and cover  350  ( FIG. 3 ). The thin layer may be stamped, or otherwise manipulated, so that at least one first spiral channel is formed on a bottom surface of the thin layer and at least one second spiral channel is formed on a top surface of the thin layer. Thus, one column capillary seal is formed between base  360  and the bottom surface of the thin layer, and another column capillary seal is formed between cover  350  and the top surface of the thin layer. In such examples, base  360  and cover  350  may be smooth, or may have formations defined to interact with the spiral channels formed respectively on the bottom surface and the top surface of the thin layer. When viewed in cross section generally perpendicular to the top and bottom surfaces) portions of the first spiral channel and the second spiral channel interleave with each other (i.e., proceeding either toward or away from a center portion of base  360 ). In other aspects, the top and the bottom surface may define channels in any of a variety of shapes, including and additionally to spiral shapes. 
     All of the above-mentioned exemplary column capillary seals may be defined by one or more surfaces in any of a variety of shapes, including and in addition to spiral shapes. For example, channels may have various radii of curvature, they may be straight, partially curved and partially straight, or any of a variety of other characteristics within the contemplation of one of ordinary skill in the art. Also, any such channels may taper in a width dimension, a height dimension, or in both width and height dimensions. 
     A characteristic of exemplary capillary seals  355   a  and  355   b  (and hence, capillary seal  355 ) is that each has a relatively long length compared with a width (a length viewed as though the spiral shape were “unwound”). Referring back to  FIGS. 2   a/b , it is apparent that prior art capillary seal  210  is wider compared with its length than are capillary seals  355   a  and  355   b.    
     Another characteristic of exemplary capillary seals  355   a  and  355   b  (and hence, capillary seal  355 ) is their respective cross-sections. Samples of each capillary seal  355   a  and  355   b  cross-section (such samples conveniently referred to herein as cross-sections) may be taken at an arbitrary point along respective lengths of capillary seals  355   a  and  355   b  (i.e., along each channel of each of capillary seals  355   a  and  355   b ). Cross-sections may be locally perpendicular to a side wall of the channels or at an arbitrary angle with respect to such channel side walls (not separately indicated in  FIGS. 4   a  and  4   b ). 
     With further regard to aspects of cross-sections of exemplary column shaped capillary seals, these cross-sections may be specified by specifying a dimension of an outer boundary without regard to an inner boundary, rather than by requiring specification of both outer boundary and inner boundary dimensions, as in the case of typical annular cross-section prior art capillary seals, such in  FIG. 2   a/b . Exemplary shapes for some such cross-sections are illustrated in  FIGS. 5   a - c.    
     Dashed lines represent a portion of the cross-section that, for an operational motor, may be provided by any opposing surface, including surfaces that are relatively stationary and relatively rotating with respect to the channels. By example, the dashed line may represent cover  350 . During assembly of the motor and during construction of components of the motor, the dashed line may represent an imaginary line across the channel for completing the channel cross-section. Cross-section shapes other than those illustrated are possible. 
     In addition to the shape of cross-sections of capillary seals  355   a  and  355   b , another characteristic is the area (size) of the cross-sections. Cross-sections of capillary seals  355   a  and  355   b  taken closer to vent openings  370   a  and  370   b  have a larger area than cross-sections taken closer to bearing openings  365   a  and  365   b . This difference in cross-section area is generally referred to as a taper of a capillary seal. Such taper may be smooth, such that the cross-section area gradually decreases from vent openings to bearing openings. The taper may be linear or non-linear. 
     Capillary seal  355  may be characterized as being column shaped by virtue of its being relatively long compared with the area of its cross-section. Capillary seal  355  is also distinguished by virtue of its cross-section being topologically equivalent to a circle at least one point along capillary seal  355  (i.e., if a cross-section of capillary seal  355  were to be taken at mechanically possible intervals, at least one of those cross-sections would be topologically equivalent to a circle). Thus, a portion of capillary seal  355  (i.e., a channel of capillary seal  355 ) may have a cross-section shaped like a rectangle, a circle, a semi-circle, a triangle, a trapezoid, or equivalent shape (some of which are illustrated in  FIGS. 5   a - c ). 
     It is contemplated that a column shaped capillary seal, such as capillary seal  355 , may have a cross-section qualitatively topologically equivalent to a circle. For example, where an outer boundary of the cross-section is substantially greater than an inner boundary of the cross-section, but where the inner boundary remains present. Such exemplary cross-sections may not strictly be considered topologically equivalent to a circle, but capillary seals having such a cross-section would be expected to function substantially similarly to capillary seals that do have a cross section topologically equivalent to a circle. 
       FIG. 4   b  illustrates another exemplary column shaped capillary seal configuration that may be used in exemplary motor  300  of  FIG. 3 . A portion of base  360  is illustrated. A circumferential trench  481  is formed about a plurality of column shaped capillary seals  483   a - d . Each column shaped capillary seal includes a respective vent openings  484   a - d  in fluidic communication (including gaseous fluids) with circumferential trench  481  and respective hydrodynamic bearing openings (not separately indicated) defined proximate central portion  405 . As illustrated, each column shaped capillary seal  483   a - d  is curved and radiates from near central portion  405  towards circumferential trench  481 . Each column shaped capillary seal  483   a - d  tapers from a larger cross-section area at respective vent openings  484   a - d  to a smaller cross-section area at respective hydrodynamic bearing openings. 
       FIG. 4   b  further illustrates cover  486  formed for a disposition over the portion of base  360  illustrated. Cover  486  includes vent  487 , which is disposed during motor assembly for fluidic communication (including gaseous fluids) with circumferential trench  481 . Vent  487  provides fluidic communication for column shaped capillary seals  483   a - d  to ambient environment  380 . Exemplary cover  486  also includes a shaft hole  488  for shaft  305 . In some examples, a shaft may be disposed on cover  486  or in an indentation portion of cover  486  formed for accepting that shaft rather than extending through shaft hole  488 , so long as fluidic communication between column shaped capillary seals  483   a - d  and hydrodynamic bearing regions  320  is provided by some other means. If desired, cover  486  may be adapted to rotate with or relative to base  360 . 
       FIGS. 5   a - c  illustrate exemplary cross-sections of channels of exemplary column shaped capillary seals  355   a  and  355   b .  FIG. 5   a  illustrates a generally rectangular cross-section  505  (which is topologically equivalent to a circle). Bottom portion  506  and first side wall portion  507  and second side wall portion  508  may be formed by removing material from a surface, such as base  360 . Top portion  508  may be supplied by an opposing surface.  FIG. 5   b  illustrates a triangular shaped cross-section  510 . First side wall portion  511  and second side wall portion  512  may be formed by removing material from a surface, such as base  360 .  FIG. 5   c  illustrates a trapezoidal shaped cross-section  515 . First side wall portion  516 , second side wall portion  517 , and bottom portion  518  may be formed by removing material from a surface, such as base  360 . As described above, capillary seal cross-sections may taper along a length of a channel of the capillary seal. Depending on a shape of the cross-section, one or more dimensions of the cross-section may change in order to accomplish this taper. By example, in regard to the rectangular cross-section  505  of  FIG. 5   a , a width of bottom portion  506  may be changed. A height of side wall portion  507  and/or side wall portion  508  may also be changed. For semi-circular or circular type cross-sections, a radial dimension may be changed. Different dimensions or different portions of a given cross-section may be changed at different points along the channel to effect a taper. By example, a height dimension may change in one portion and a width dimension in another. By further example, a radial dimension may be changed non-uniformly such that a semi-circle cross-section becomes semi-elliptical along a channel. Other variations are within the scope of one of ordinary skill in the art. 
     Generally, a distinction between cross-sections of  FIGS. 5   a - c  and many prior art capillary seals is that the cross-section of known prior art capillary seals are topologically equivalent to an annular surface rather than a circle (as discussed with regard to  FIGS. 2   a/b ). Exemplary channels having the afore-mentioned cross-section topology at one point along the channel need not have this cross-section topology at other points where a cross-section may be taken. For instance, other cross-sections of such a channel may be topologically equivalent to a annular surface. 
     Now turning to  FIG. 6 , a vertical cross-section of another exemplary spindle motor  600  is illustrated. The exemplary motor  600  includes a shaft  605 , and a co-axially disposed hub  610  coupled with shaft  605 . A sleeve  615  and shaft  605  interface to form hydrodynamic bearing regions  620 , which supports rotation of shaft  605  and hub  610  about sleeve  615 . Sleeve  615  has an outer surface  625  that interfaces with cup  623  to form a recirculation channel  630 . A back iron  640  portion of hub  610  includes an inner surface that interfaces with an outer surface  651  of seal ring  650 . As further described below, column shaped capillary seal  655  (generally indicated with dashed lines) is defined by outer surface  651  and is disposed at the interface between the inner surface of hub  610  and the outer surface  651  of seal ring  650 . A top  652  of seal ring  650  interfaces with cup  623  to form an annular opening  645 , at which a secondary meniscus of lubricating liquid forms. Cup  623  also supports sleeve  615 . Magnet  685  couples with back iron  640  to face a stator  690  that electromagnetically interacts with magnet  685  for radially propelling hub  610  and shaft  610  about sleeve  615 . A splash guard  651  may be disposed proximate a bottom  653  of seal ring  650 . 
     As will be further discussed with regard to  FIGS. 7   a/b , capillary seal  655  includes bearing openings and vent openings. The bearing openings provide fluidic communication between capillary seal  655  and hydrodynamic bearing regions  620 . The vent openings vent capillary seal  655  to ambient environment  680 , which may contain air or another gas or mixture of gases. As illustrated, capillary seal  655  is disposed between two surfaces that do not relatively rotate with respect to each other (inner surface of hub  610  and outer surface  651  of seal ring  650 ). However, it is notable that in this example, capillary seal  655  rotates with hub  610 . Other exemplary capillary seal dispositions and configurations are possible, and some of them are further illustrated herein. 
       FIG. 7   a  illustrates an exemplary seal ring  650  and exemplary column shaped capillary seal  655  (a portion indicated). Exemplary capillary seal  655  is disposed on (or defined by) outer surface  651  of seal ring  650  in a circumferential spiral (helical) shape and comprises multiple separate channels  765   a - c  extending from vent openings  767   a - b  (additional vent openings not shown) at bottom  653  of seal ring  650  to hydrodynamic bearing openings (one hydrodynamic bearing opening  770  shown) at top  652  of seal ring  650 . As with exemplary capillary seal  355 , described with respect to  FIGS. 3 ,  4   a , and  4   b , capillary seal  655  may comprise fewer or more separate channels, wherein each channel may form a functionally distinct capillary seal or reservoir. 
       FIG. 7   b  illustrates another design for exemplary seal ring  650  and exemplary column shaped capillary seal  655  (a portion indicated). Exemplary capillary seal  655  is disposed on (or defined by) outer surface  651  of seal ring  650 . Capillary seal  655  comprises multiple separate channels  765   a - c  (additional channels not illustrated) disposed substantially parallel to an intended axis of rotation of seal ring  650  and extending from vent openings  767   a - c  (some vent openings not shown) at a bottom  653  of seal ring  650  to hydrodynamic bearing openings  770   a - c  (some hydrodynamic bearing openings not shown) at a top  652  of seal ring  650 . As with exemplary capillary seal  355 , described with respect to  FIGS. 3 ,  4   a , and  4   b , capillary seal  655  may comprise fewer or more separate channels. 
     Although  FIGS. 7   a/b  illustrate seal ring  650  with a generally cylindrical surface, on which is formed one or more column capillary seals, non-cylindrical surfaces may also be used to define column capillary seals, such surfaces may be generally conical, spherical, and the like. 
       FIG. 8  illustrates, in the context of a motor  800  cross-section, aspects of another exemplary capillary seal. Rotating hub  810  is co-axially disposed about stationary shaft  805  and interfacing surfaces of hub  810  and shaft  805  form hydrodynamic bearing regions  820 . Hydrodynamic bearing regions  820  may comprise one or more journal bearings and/or thrust bearings. Hydrodynamic bearing regions  820  vents to an ambient environment at first opening  845 , at which lubricating liquid forms a meniscus. At bearing opening  850 , hydrodynamic bearing regions  820  is in fluidic communication with capillary seal  855  (disposition of which is generally indicated by dashed lines, but which is otherwise not shown). Capillary seal  855  vents with the ambient environment via vent opening  860 . 
     Capillary seal  855  is formed in coverplate  815 , which interfaces with a top surface  811  of hub  810 . In this example, top surface  811  of hub  810  provides a covering for capillary seal  855 . In other examples, capillary seal  855  may be formed in hub  810  and coverplate  815  may provide the cover. In this example, capillary seal  855  is disposed on a member of motor  800  that rotates about a fixed member (shaft  805 ). Further, capillary seal  855  is disposed between two members that remain stationary with respect to each other (coverplate  815  and hub  810 ). Exemplary capillary seal  855  may have a planar, circumferential, or conical spiral shape, straight shapes, curved shapes, or another shape. 
     Capillary seal  855  may include one or more channel(s) (e.g., channels similar to those shown in  FIGS. 4   a  and  4   b ) formed in either hub  810  or coverplate  815 , each channel in fluidic communication with vent opening  860  (i.e., vent opening  860  may be one opening, several openings or one continuous opening disposed about a perimeter of the interface between coverplate  815  and hub  810 ). Each channel is also in fluidic communication with hydrodynamic bearing regions  820  through one or more bearing openings  850  (such as those illustrated in  FIGS. 4   a - 4   b ). The bearing openings  850  have a cross-section with a smaller area than vent openings  860  and the channel(s) may gradually taper in one or more dimensions from each respective vent opening to each respective bearing opening. The taper may be linear or non-linear. In aspects, channel cross-sections may at one or more points be topologically equivalent to a circle. Generally, lengths of the channels may be substantially greater than width and height dimensions of cross-sections of the channels. 
       FIG. 9  illustrates a vertical cross-section of a portion of a motor  900 . In aspects presented here, column shaped capillary seals may be disposed between relatively rotating members of motor  900 . Shaft  905  includes a major diameter portion  907  and a minor diameter portion  906 . Hub  910  is co-axially disposed about shaft  905  at major diameter portion  907 . Shield  915  includes outer radial portion  916  that couples with hub  910  and which supports an inner radial portion  917  disposed proximate minor diameter portion  906  of shaft  905 . Major diameter portion  907  interfaces with an inner surface of hub  910  to form hydrodynamic bearing regions  920 . 
     A radial gap  931  is formed between an outer surface of minor diameter portion  906  and an inner radial surface  917  of shield  915 . Radial gap  931  is in fluidic communication with an axial gap  930  disposed between a top surface of major diameter portion  907  and a bottom surface of shield  915 . In aspects, radial gap  931  is somewhat greater than axial gap  930  such that lubricating liquid preferentially seeks axial gap  930 . A column shaped capillary seal  955  (indicated in cross-section in  FIG. 9 ) is in fluidic communication with axial gap  930  and hydrodynamic bearing regions  920 . Cross-sections of portions of the capillary seal are illustrated in  FIG. 9 , including large cross-section portion  941  and smaller cross-section portion  942 . A fill hole  935  for lubricating liquid is disposed in shield  915 , near large cross-section portion  941 . 
     Capillary seal  955  is further illustrated in  FIG. 10 .  FIG. 10  illustrates an exemplary bottom surface  1010  of shield  915 . As illustrated in cross-section  FIG. 9 , inner radial surface  917  is formed to create radial gap  931 . Pumping grooves  1015  are disposed on bottom surface  1010  and configured to pump lubricating liquid away from radial gap  931  and the central hole.  FIG. 10  illustrates that large cross-section portion  941  and small cross-section portion  942  of capillary seal  955  result from a channel  1056  formed in bottom surface  1010 . In aspects, channel  1056  gradually tapers in depth and/or width from large cross-section portion  942  to small cross-section portion  941 . Large and small cross-section portions may also be known respectively as wide and narrow portions. Channel  1056  may taper in a width dimension, a height dimension, or in some combination of width and height dimensions. 
     As illustrated in  FIG. 10 , capillary seal  955  includes a channel  1056  having a cross-section that is generally topologically equivalent to a circle at one or more points along channel  1056  (such as large cross-section portion  941  and large cross-section portion  942 ). Here, the cross-section may be defined by channel  1056  and the opposing top surface of major diameter portion  907 , without considering axial gap  930 . 
     Also, a length dimension of capillary seal  955  is relatively large compared with dimensions defining its cross-section. As with other aspects illustrated herein, precise distinctions relating to ratios of lengths to other dimensions is not intended nor required. Rather those of skill in the art would understand that prior art capillary seals are typically more functionally limited (constrained) as to ratios of lengths to other dimensions. Such functional limitations are due to sizing constraints of particular motor designs, a desired volume of lubricating liquid to be stored, desired seal robustness, and other such considerations. 
     In exemplary operation, shield  915  and hub  910  rotate relative to shaft  905 . Such relative rotation creates shear forces that urge lubricating liquid disposed in channel  1056  towards small cross-section portion  941 . Pumping grooves  1015  urge lubricating liquid from radial gap  931  into capillary seal  955  (channel  1056  of  FIG. 10 ). Thus capillary seal  955  maintains a ready supply of lubricating liquid for hydrodynamic bearing regions  920  while keeping lubricating liquid from both fill hole  935  and radial gap  931 . Capillary reservoirs having characteristics of capillary seal  955  may be disposed in other locations within a FDB motor, such as near a bottom of a hub or a shaft rather than near a top, such as illustrated herein. 
     Characteristics of capillary seal  955  may be varied as well. For example, flat portion  1020  in  FIG. 10  separates large cross-section portion  942  from small cross-section portion  941 . Flat portion  1020  may be defined at different locations relative to cross section portions  942  and  941 . For example, flat portion  1020  may be disposed generally radially opposite vent  935  in channel  1056 , thereby effectively dividing channel  1056  at that point. In such an example, channel  1056  may be designed to taper along each side of channel  1056 . The taper would typically be in one or more of a width and height dimension of channel  1056  from larger dimensions proximate vent  935  to smaller dimensions proximate flat portion  1020 . Such an example would functionally create two channels, each having its own meniscus in a different portion of channel  1056 . 
       FIG. 11  illustrates a top surface  1105  of shield  915  with fill hole  935  and inner radial surface  917  illustrated. Top surface  1105  as illustrated is smooth, but it may be adapted as desired to be non-smooth in any number of ways. 
     Motor members and portions of motor members described herein may be formed, worked, and otherwise manipulated in accordance with aspects described above by any of a variety of methods and means, including electro-chemical etching, stamping, milling, injection molding, and the like. Various methods and means may be used at different stages of production. Selection of particular production means and methods based on the disclosure herein is within the scope of one of ordinary skill in the art. 
     Various motor and capillary seal aspects have been illustrated and described herein. In some figures, rotating shaft designs have been presented while in others, fixed shaft designs have been presented. One of ordinary skill in the art would understand that teachings related to each may be adapted to the other design. Also, it would be understood that certain components have been separately identified herein, but such identification does not imply that such components must be separately formed from other components. Similarly, components identified herein may be subdivided into sub-components in other designs. Additionally, features such as recirculation channels, bearing surfaces, pumping grooves, and the like may be disposed additionally or differently than presented in aspects herein. 
     Other modifications and variations would also be apparent to those of ordinary skill in the art from the exemplary aspects presented. By example, various exemplary methods and systems described herein may be used alone or in combination with various fluid dynamic bearing and capillary seal systems and methods. Additionally, particular examples have been discussed and how these examples are thought to address certain disadvantages in related art. This discussion is not meant, however, to restrict the various examples to methods and/or systems that actually address or solve the disadvantages.