Abstract:
A take-up reel for use in a tape drive for minimizing print through errors, or data transfer from one layer of tape on the take-up reel to an adjacent layer of tape on the take-up reel. The take-up reel is configured to allowing portions of the buckle, coupling the take-up leader to the supply leader, to recess into the take-up reel. The relatively even and concentric configuration of leaders tape and buckle when wound onto the take-up reel prevents the application of significant non-uniform pressure to the data tape wound thereover, which reduces print through sources of data error.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to magnetic recording tape reels. More particularly, the present invention relates to a tape reel that reduces print through errors on data tape wound onto the reel when used in association with a buckle between the take-up leader and the supply leader. 
     DESCRIPTION OF THE PRIOR ART 
     Magnetic tapes are used for data storage in computer systems requiring data removability, high data rate capability, high volumetric efficiency, and reusability. The use of magnetic tape data storage devices is commonplace, as the cost per unit of stored data is low compared to other forms of electronic data storage, and magnetic tape devices are frequently used to back-up or preserve data stored on more expensive-non-removable disk drives. 
     Magnetic tape formats include open reels, tape cartridges and cassettes. In the past, it was common to use a simple open reel including a hub upon which the tape was wound and flanges that protect the edges of the tape. However, the need for additional tape protection and a desire for a reduction in the need for human intervention in installing or replacing data tapes in tape data storage devices has led to the increased use of tape cartridges and cassettes. A typical magnetic tape includes a polymer film substrate with a coating of magnetic recording material on one side, and a non-stick coating of material on the other side to reduce adhesion between layers of tape wound on a reel. In a typical tape drive using tape cartridges, the tape runs between a rotatable supply reel housed within the tape cartridge and a take-up reel in the tape drive assembly. When the cartridge is inserted into the tape drive, a take-up leader on the take-up reel is coupled to the supply leader, which is further coupled to the tape on which the data is stored. The procedure of coupling the take-up leader to the supply leader is known as buckling. Once the two leaders are coupled, the data tape is pulled through the tape path to the take-up reel by the take-up leader. 
     There is an increasing need for tape data storage devices that provide greater data storage capacity and higher data transfer rates. To satisfy the requirement for data storage, higher track densities on the magnetic tape are sought. The greater the track density, the greater the volume of information that may be stored on the tape. Accordingly, the width of tracks and separation between tracks has continued to decrease in order to accommodate more data tracks. However, as data tracks narrow, the signal strength from the tracks decreases. Therefore, even minor magnetic influences can mask or distort the magnetic data on a data tape sufficiently that data is lost. 
     There are a variety of sources of such data errors or losses. One source of data error is called print through, which results when non-uniform pressure distribution is applied to tape media as it resides on the reel. Print through is the tendency of the magnetic information stored on a layer of tape to be influenced by the magnetic data stored on an adjacent layer of tape, but will be used herein to include embossing sources of error as well. Magnetic tape in tape drives may be wound tightly. For example, in DLT™ tape drives made by Quantum Corporation, magnetic tape wound on a reel may experience pressure between 200-400 psi towards the central axis of the reel. Experimental results have shown that even small deviations from circularity of the reel may cause localized pressures experienced by the magnetic tape to exceed 1,000 psi. The non-magnetic layer of most tape, which may normally be relied on to minimize print through, is not capable of sufficiently shielding the magnetic layers of adjacent tapes in such non-uniform pressure environments. Non-uniform pressure regions can propagate outward as the reel winds additional layers of tape. This is called lateral runout, and can result in significant data loss. One source of non-uniform pressure occurs in association with the buckle between the take-up leader and the supply leader used on single-reel data tape cartridges. For example, differences between the buckle and the thickness of the take-up leader or the supply leader may create regions of uneven pressure distribution, which may result in print through. 
     What is needed is a take-up reel configured to reduce print through errors on tape wound thereon by improving the circularity of the surface presented for winding data tape. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a take-up reel including a hub configured to improve circularity and thus reduce print through errors on tape wound thereon by allowing portions of the buckle to recess into the take-up reel. The particular configuration of the take-up reel may be adapted for use with a buckle configuration. A preferred embodiment of the take-up reel of the invention will be described for use on the buckle shown in FIG.  2 . However, the invention could be easily adapted by one skilled in the art for use with other buckle configurations. 
     In one embodiment of the reel, the hub includes a circumferential peripheral surface with a circumference of the peripheral surface defined by a first radius. At least one raised ridge is formed on one portion of the peripheral surface of the hub with an outer surface of the ridge defined by a radius larger than the radius of the peripheral surface. The ridge preferably has a width less than the width of the peripheral surface, and includes a pair of grooves with a length perpendicular to the edge of the peripheral surface. Two flattened regions are preferably formed on each side of the ridge, meeting at a crest located at approximately the center of the arc of the ridge. The reel also preferably includes a take-up leader with apertures sized and positioned to accept the ridge or other structures on the peripheral surface of the hub. 
     As the buckle is wound onto the hub, at least one layer of take-up leader is preferably wound onto the peripheral surface of the hub between the buckle and the peripheral surface of the hub. Subsequent layers of tape wound thereover are supported by one or more of the following: (a) the previous layers of tape wound over the peripheral surface of the hub and the flattened regions, (b) the portions of the buckle recessed into the hub so that an outer surface of the buckle is approximately aligned with the outer surface of the ridge, (c) and the outer surface of the ridge itself. The layers of tape wound immediately over the supporting structures previously described are intended to present a surface that is highly circular for winding subsequent layers of magnetic tape, thus minimizing potential for print through as the tape is wound thereon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing of a generic tape drive using the take-up reel of the invention. 
     FIG. 2 a  is a top isometric view of a buckle for use in association with the take-up reel of the invention. 
     FIG. 2 b  is a bottom isometric view of a buckle for use in association with the take-up reel of the invention. 
     FIG. 3 is an isometric view of an embodiment of the take-up leader of the take-up reel of the invention. 
     FIG. 4 is an isometric view of the take-up reel of the invention. 
     FIG. 5 is a top plan view of the take-up reel of FIG.  4 . 
     FIG. 6 is a side view of the take-up reel of FIG.  4 . 
     FIG. 7 is an isometric view of the take-up reel of FIG. 4 with the take-up leader coupled to the supply leader and take-up leader partially wound on the take-up reel. 
     FIG. 8 is a side view of a section of the take-up reel showing several layers of take-up leader, supply leader, and data tape wound thereon. 
     FIG. 9 is a side view of the take-up reel including guide bars and flanges. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a take-up reel configured to reduce print through errors on tape wound thereon by allowing portions of the buckle to recess into the take-up reel. The particular configuration of the take-up reel may be adapted for use with a desired buckle configuration. For purposes of explanation, the take-up reel of the invention will be described for use on a buckle configuration shown in FIG.  2 . However, the invention could be adapted for use with other buckle configurations. Furthermore, preferred dimensions will be given for the take-up reel of the invention configured for use in a tape drive that accepts cartridges supplying approximately 0.5 inch magnetic tape. However, one skilled in the art could easily adjust the dimensions of the take-up reel of the invention for use with data tape of different dimensions. 
     With reference to FIG. 1, a generic tape drive  100  and cartridge  106  are shown. The tape drive  100  includes the take-up reel  300  of the invention, rollers  102  and the magnetic head  104 . The take-up reel  300  includes a take-up leader that is coupled to a supply leader extending from one end of data tape wound on a rotatable supply reel  108  within the cartridge  106 , when the cartridge  106  is inserted into the tape drive  100 . The term magnetic tape will be used hereafter to refer to both the supply leader and the data tape on which data is stored, and will be referenced by the number  110 . To read or write data to the magnetic tape  110 , the magnetic tape  110  is spooled between the take-up reel  300  and the supply reel  108 , with rollers  102  guiding the magnetic tape  110  over the magnetic head  104 . The configuration of the tape drive  100  is shown only by way of example, and the take-up reel  300  of the invention could be used in other tape drive configurations. 
     Referring to FIGS. 2 a  and  2   b,  the buckle  200  comprises two cylindrical components that extend through the tape path approximately perpendicular to the tape path. FIG. 2 a  is a top view of the buckle  200 , and FIG. 2 b  is a bottom view of the buckle. The first cylindrical component  202  is coupled to the take-up leader  206 , and the second cylindrical component  204  is couple to the supply leader  208 . The first and second cylindrical components  202 ,  204  further extend or protrude some distance beyond the edges of the leaders  206  and  208  on each side of the tape path. The ends of the second cylindrical component  204  are pivotally coupled to a first and second hook means  210  and  212 . In the embodiment shown, the hooks  210 ,  212  are curved in a banana shape, and include recesses  214 , best seen in FIG. 2 b,  on each hook component  210 ,  212  for grabbing the protruding ends of the first cylindrical component  202  and guiding them into place. However, in alternate embodiments, other configurations of the buckle  200  may be used, with corresponding modification to the take-up reel  300  of the invention. 
     The cylindrical components  202  and  204  may be coupled to the ends of the leaders  206  and  208  respectively, by any known means, including forming a loop of material around the cylindrical components and affixing the layers together, as shown in FIG. 2, by use of an adhesive, heat weld, or other known means for bonding the two layers. The cylindrical components  202 ,  204  are preferably circular in cross section, however, other cross section shapes may be used, including oval or elliptical. The diameters of the cylindrical components  202 ,  204  are preferably between 0.015 and 0.050 inches, and more preferably approximately 0.025 inches. Any desired materials may be used in fabricating the buckle components, and acceptable materials for such uses are well known. 
     FIG. 3 shows a take-up leader  206  buckled to the supply leader  208  in isolation from take-up reel  300 . The materials used in manufacturing the take-up leader  206 , the supply leader  208 , and the magnetic tape on which data is stored (the data tape), are preferably formed of a polymer substrate such as MYLAR®, however, other materials may be used. The data tape will preferably include a magnetic coating on one side of the tape, and a non-stick coating on the other to reduce adhesion between layers of tape would on a reel. The materials used to fabricate the take-up leader  206 , the supply leader  208 , and the data tape may be the same or different, and acceptable tape for the various uses are commercially available. The take-up leader  206  and the supply leader  208  are preferably approximately 0.500 inches to 0.502 inches in width, and 0.005 to 0.008 inches in thickness. The data tape is preferably 0.498 to 0.500 inches wide, and 0.015 to 0.003 inches thick. In alternate embodiments different dimensions may be used. Means for joining the supply leader  206  to the data tape are well known, and any desired means for splicing the supply leader  206  to the data tape may be used. The preferred width of the take-up leader and the magnetic tape  110  is approximately 0.5 inches, which typically means that the width of the data tape will range from a maximum of 0.498 inches to a minimum of 0.496 inches. The width of the leaders  206 ,  208  preferably ranges between 0.500 and 0.502 inches, and the thickness between 0.004 inches and 0.008 inches, but more preferably approximately 0.0075 inches thick. The thickness of the data tape preferably ranges between 0.0001 and 0.0003 inches, and is more preferably approximately 0.0002 inches thick. However, in alternate embodiments leaders and magnetic tape of other dimensions may be used. Some changes in dimension may require that the take-up reel  300  of the invention be adapted accordingly. The mushroom shaped protrusion  216  is formed from the material used to fabricate the take-up leader  206 , and is intended to provide a backward compatible means for coupling to supply leaders of older design. Gaps  218 , best seen in FIGS. 2 a  and  2   b,  are formed on either side of the mushroom shaped protrusion  216  on the take-up leader  206 , the use of which will be later explained. The take-up leader  206  further includes an end aperture  220  used to couple the take-up leader  206  to the take-up reel  300 , and several rectangular apertures  222  that fit over structures on the outer or peripheral surface of the hub of the take-up reel  300 , the uses of which will be explained in more detail below. The supply leader  208  likewise includes an aperture  224 , best seen in FIGS. 2 a  and  2   b,  that fits around structures on the peripheral surface of the hub. The gaps  218  and the aperture  224  of the supply leader  208  are sometimes individually and/or collectively referred to herein as openings. 
     With reference to FIG. 4, a take-up reel  300  of the invention is shown configured for use with the buckle shown in FIGS. 2 a  and  2   b.  The take-up reel  300  preferably comprises a hub  302  with a central axis of rotation. The overall length of the hub is not critical to the invention, so long as there is enough surface to support the tape to be wound thereon, however, the length of the hub  302  along the axis of rotation is preferably between 1.0 inch and 2.0 inches, and is more preferably approximately 1.55 inches. The hub is preferably fabricated using a polycarbonate with approximately 30% glass, however, other materials may be useable. One or both ends of the hub  302  are configured to couple to a means for rotating the hub  302  around the axis of rotation  304 . The configuration used to couple to the rotation means, and the rotation means used, are not critical to the invention, and any known combination of rotation means and means for coupling the hub  302  to the rotation means may be used. The hub  302  includes a circumferential or peripheral surface  306  for winding magnetic tape  110 . The peripheral surface  308  is preferably slightly wider than the take-up leader  206  intended to be used in association with the take-up reel  300 . For use with 0.5 inch tape, the width of the peripheral surface  306  is preferably between 0.502 inches and 0.504 inches, but more preferably approximately 0.502 inches in width, although in other embodiments, different ranges may be preferred. Preferably 75% to 95%, and more preferably approximately 82%, of the circumference of the peripheral surface  306  is defined by a first radius, with the remaining peripheral surface comprising a curved ridge  308  having an outer surface defined by a second larger radius. 
     The take-up reel  300  further comprises a means for coupling one end of the take-up leader  206  to the hub  302 . Any known means for coupling the take-up leader to the hub  302  may be used. In an embodiment shown in FIG. 4, a slot  312  penetrates from the bottom of the notch  310  to a cavity  314  within the body of the hub  302 . A hook means  316  extends from a surface of the cavity  314  around which the end aperture  220  of the take-up leader  206  is looped. One side of the notch  310  is curved gradually outward until it reaches the circumference of the peripheral surface  306  defined by the first diameter. The slope is intended to introduce the take-up leader  206  to the peripheral surface  308  without creating a sharp bend in the magnetic tape  110  that may propagate through subsequent layers. When viewed from the bottom of the hub  302 , as seen in FIG. 4, the take-up leader  206  is wound in a counterclockwise direction, and thus, the gradual curve assists in minimizing the generation of uneven pressure distribution applied to the magnetic tape  110  wound thereover. 
     With reference to FIG. 5, the curved ridge  308  preferably has a length between 0.06 inches and 1.30 inches, and more preferably approximately 0.095 inches. The length of the diameter defining the curved ridge  308  depends on the number of layers of take-up lead  206  that will be wound on the take-up reel  300 . In a preferred embodiment of the take-up leader  206  disclosed in FIG. 3, the take-up leader  206  is designed to encounter the curved ridge  308  three times. Therefore, the preferred radius defining the arc of the curved ridge  308  is approximately three times the thickness of the take-up leader for which the hub is intended to be used. For example, if the thickness of the take-up leader  206  is approximately 0.0075 inches, then the diameter of the arc defining the curved ridge  308  is equal to the diameter defining the peripheral surface  306  plus three times 0.0075 inches. 
     A pair of flattened regions  320  cut cords across a length of the circumference of the peripheral surface  306  of the take-up reel  300  on each side of the curved ridge  308 , as can be seen in FIG. 6, which is side view of the hub of FIG.  4 . The pair of flattened regions  320  can be seen on each side of the ridge  308 , with grooves  326  extending across the curved ridge  308  between opposite flattened regions  320 . The width of the curved ridge  308  is preferably between 0.100 inches and 0.300 inches wide, and more preferably approximately 0.200 inches wide. The flattened regions  320  are preferably between 0.100 inches and 0.200 inches wide, and more preferably approximately 0.150 inches wide. The flattened regions  320  are preferably between 0.300 inches and 0.700 inches in length, and more preferably 0.500 inches in length. Because the flattened regions  320  cut a cord across the circumference of the peripheral surface  308  of the hub  302 , the length of the flattened regions  320  are related to the diameter of the cylindrical components  202 ,  204  that must be accommodated. Referring again to FIG.  5  and also with reference to FIG. 8, the distance from the surface of the flattened regions  320  to the outer surface of the curved ridge  308 , measured at the center point of each flattened region  320 , is preferably four times the thickness of the take-up leader  206  or plus the diameter of the cylindrical components of the buckle; specifically, two layers of take-up leader  206  lying over the flattened regions  320 , two layers of take-up leader  206 , to account for the single layer of take-up leader  206  looped around the circumference of a cylindrical component  202  or  204  and therefore counting as two layers, and the diameter of the cylindrical component  202  or  204 . For example, in an embodiment of the hub  302  for use with a take-up leader  206  with a thickness of 0.0075 inches, and a cylindrical component  202  with a diameter of 0.025 inches, the distance from the flattened region to an arc defined by the surface of the curved ridge  308  is approximately ((4)(0.0075))+0.0250=0.0475 inches. The calculation is the same for the gap  318  that accepts the cylindrical component  204  coupled to the supply leader  208 , if, as in the preferred embodiment, the supply leader  208  is of the same thickness as the take-up leader  206 . 
     A shoulder exists at each end of the curved ridge  308 , with one shoulder designated  324 , and the other  332 . Each shoulder  324 ,  332  has a height preferably approximately three times the thickness of the take-up leader  206 , so that on the third circumference of the take-up leader  206  the three layers of take-up leader  206  are approximately even with the outer surface of the curved ridge  308  at the shoulder  324  encountered by the take-up leader. Similarly, as the first layer of supply leader encounters the other shoulder  332 , there are preferably  2  layers of take-up leader, and one layer of supply leader, which preferably brings the outer surface of the supply leader  206  approximately even with the outer surface of the curved ridge  308 . Thus, the surface presented to the subsequent layers of supply leader  208  will be defined by an approximately uniform diameter, approximately equal to the diameter defining the arc of the curved ridge  308 , preferably providing near circularity. In an embodiment using a take-up leader 0.0075 inches thick, the shoulders  324 ,  332  will have a height of 0.0225 inches. 
     Two grooves  326  are formed in the outer surface of curved ridge  308 , extending approximately perpendicular to the arc of the curved ridge  308 , and extending between opposite flattened regions  320  on each side of the curved ridge  308 . The depth of the grooves  326  is preferably slightly larger than the diameter of the cylindrical component  202  or  204  intended to be used therewith. The openings of the groove are preferably between 0.050 inches and 0.150 inches, and more preferably approximately 0.125 inches, depending on the size of the cylindrical components  202 ,  204  used. The sides of the grooves  326  will preferably include relief angles between 0 degrees and 35 degrees, and more preferably 20 degrees. The grooves  326  are preferably positioned so that when cylindrical component  202  or  204  is accepted within one of the grooves  326 , a centerline of the cylindrical component  202  or  204  will be approximately aligned with a center of the flattened region  320 . The bottom of the grooves  326  are preferably positioned a distance from a plane defined by the associated flattened sections  320  equal to two times the thickness of the magnetic tape  110 . In some embodiments, it may be preferable that the cylindrical components  202 ,  204  rest on the layers of take-up leader  206  lying over the flattened regions  320 , to prevent any deformation of the cylindrical components  202  or  204 , by forces applied by subsequent layers of magnetic tape  110 . 
     Referring to FIG. 7, a take-up leader  206  of the hub  302  is shown coupled by the buckle  200  to the supply leader  208 , and partially wound around the peripheral surface  306  of the hub  302 . The take-up leader  206  has been wound twice around the hub  302 , and the cylindrical components  202 ,  204  of the buckle  200  are in position to enter the grooves  326 , as the take-up leader  206  is further wound onto the hub  302 . 
     FIG. 8 shows a side view of the hub  302  of FIG. 7 after several more revolutions of the hub  302 . The cylindrical components  202 ,  204  of the buckle disclosed in FIG. 2 a  and  2   b  have been received within the grooves  326 , and several subsequent layers of the supply leader  208  have been wrapped thereon. In the preferred configuration shown, two layers of take-up leader  206  are wound around the peripheral surface  306  of the hub  302 , with the rectangular apertures  222  aligned with the curved ridge  308  so that the take-up leader  206  lies only over the flattened regions  320  on either side of the curved ridge  308 . The third layer of take-up leader  206  brings the layers of take-up leader  206  approximately level with, or only slightly below, the peripheral surface of the curved ridge  308  at one of the shoulders  324 . Similarly, the buckle aperture  224  of the supply leader  208  allows that supply leader  208  to lie on either side of the curved ridge  308 , and the first layer of supply leader  208  brings the two layers of take-up leader  206  and the layer of supply leader  208  approximately level with, or only slightly below, the peripheral surface of the curved ridge  308 . In this embodiment, it is important to allow the outer surface of the buckle  200  to recess into the hub  302  at a level equal to, or slightly below, the outer peripheral surface  306  of a nominal radius of the hub  302 . In embodiments of the buckle  200  including the mushroom shaped protrusion  216 , the protrusion lies over a portion of the outer surface of the curved ridge  309 . 
     The cylindrical component  202  of the take-up leader  206  has entered one of the grooves  326 , and the cylindrical component  204  of the supply leader  208  has entered the other groove  326 . The ends of the cylindrical components  202  and  204  extending beyond the sides of the ridge  308  preferably rest on the previous layers of take-up leader  206  wound over the flattened regions  320  of the hub  302 , although in alternate embodiments this may not be necessary. The crest  322  between the flattened regions  320  supports two layers of take-up leader  206 , which brings the surface of the second layer of the take-up leader  206  approximately level with the center of the area of the curved ridge  308 . The first layer of supply leader  208  is therefore supported over the arc of the curved ridge  308  by the outer surface of the curved ridge  308 , the ends of the cylindrical component  202 ,  204  extending from the grooves  326 , and the take-up leader  206  lying over the crests  322  between the pairs of flattened regions  320 . The layers of supply leader  208  wound over the supporting structures previously described are intended to present a surface for data tape that is highly circular, thus minimizing potential for print through as the tape is wound thereon. 
     In alternate embodiments more or less layers of the take-up or supply leaders  206 ,  208  may be used. Specifically, in alternate embodiments, one or more than two layers of take-up leader  206  may be used prior to the buckle  200  entering the wound position, and one or more than two layers of supply leader  208  may be used. 
     Referring to FIG. 9, in some preferred embodiments the take-up reel  300  will also include guide bars  328  for insuring uniform stacking of the magnetic tape  11  laterally on the peripheral surface  306  of the hub  302  and flanges  330  to prevent the magnetic tape  110  from dropping significantly below a plane defined by an edge of the peripheral surface  306  of the hub  302 . Preferred embodiments of the hub  302  may include a pair of grooves  318 , best seen in FIG. 4, formed on opposite sides of the peripheral surface  306  of the hub  302  for partially accepting guide bars  328  preferably extending radially from central axis of the hub  302  for guiding tape wound on the hub  302  to stack uniformly. In a preferred embodiment, guide bars  328  are coupled to the hub  302  on each side of the hub  302  extending outward from the central axis  304  of the hub  302  a selected distance beyond the peripheral surface  306  of the hub  302 . As the width of the peripheral surface  306  is slightly wider than the maximum width of the magnetic tape  110  used, the grooves  318  allow the guide bars  328  to be spaced more closely approximating the width of the magnetic tape  110 , preferably approximately 0.502 inches. The spacing of the guide bars  328  assists the magnetic tape  110  to stack uniformly. However, the grooves  318  and guide bars  328  are not critical to the invention, and other known means for guiding the uniform stacking of tape on a reel may be used. The flanges  330  may also be provided on each side of the peripheral surface  306  of the hub  302  and extend radially from the central axis  304  of the hub  302 . As guide bars  328  are used to provide uniform stacking of magnetic tape  110 , the purpose of the flanges  330  is primarily to prevent any portion of the magnetic tape  110  from dropping significantly below a plane defined by an edge of the peripheral surface  306  of the hub  302  in the event that the magnetic tape  110  becomes slack. The flanges  330  are not critical to the invention, and other known means for preventing the magnetic tape  110  from dropping away for peripheral surface  306  of the hub  302  may be used. 
     To those skilled in the art, many changes and modifications will be readily apparent from consideration of the foregoing description of a preferred embodiment without departure from the spirit of the present invention; the scope thereof being more particularly pointed out by the following claims. The description herein and the disclosures hereof are by way of illustration only and should not be construed as limiting the scope of the present invention which is more particularly pointed out by the following claims.