Abstract:
A head for a tape drive system has a plurality of transducers formed on a substrate and protected by a cover bar, with a tie bar bonded to the cover bar. The tie bar extends along a tape-facing surface beyond the cover bar, enhancing the structural integrity of the head. Wear bars may be bonded to the substrate, cover bar and tie bar. Alternatively, the tie bar may have a notch within which the substrate and cover bar are bonded. The tie bar reduces misalignment and instability of the transducers, providing increased storage capacity and greater reliability and durability of the tape drive system.

Description:
TECHNICAL FIELD 
     The present invention relates to heads or transducers for tape drive storage systems. 
     BACKGROUND OF THE INVENTION 
     Multichannel or multitrack tape drives have been known for many years. Currently, such drives may be employed for audio, video or computer applications, and may read and write signals in analogue or digital form. 
     The rapid growth of the Internet has fostered a need for inexpensive data backup systems, for which tape drives have been employed. The increasing need for data storage, however, has placed increasing demands on tape drive storage capacity. To satisfy this need for storage, spacing between tracks can be reduced, more tracks can be provided on each tape, bits can be packed more closely on each track, or tape speed and/or length can be increased. Unfortunately, rapidly moving tapes and heads do not always accurately read or write data as these modifications are made to increase storage capacity. 
     FIG. 1 shows several prior art tape-head components  20  before assembly and finishing. The components  20  include a number of microscopic transducers  22  that have been formed along a surface  24  of a substrate  25  that has been covered with a cover bar or head cap  27 . Numerous process steps have been performed to create the transducers  22  on the substrate  25 , making this component relatively expensive. The cover bar  27  protects the expensive transducers  22 . Wear bars  30  and  33  are positioned adjacent ends of the joined substrate  25 , transducers  22  and cover bar  27 , to which the wear bars are to be bonded. The wear bars provide a cost-effective means for extending the surface of the tape-head that contacts the tape. After adding the wear bars, the bonded substrate and wear bars are fit into a bed  35  that holds the components together. An aperture  34  in the bed  35  allows for insertion of a flex-cable, not shown, containing leads connecting to transducers  22  along surface  24 . 
     FIG. 2 shows a finished tape-head assembly  40  made from the components of FIG. 1. A pair of rails  37  and  39  are formed on a tape-facing surface  44  of the assembly. Although this device has performed adequately, challenges in reducing tolerances and errors exist, so that increasing data storage density and reducing access time has been difficult. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide increased micro-mechanical accuracy in a tape-head assembly for a tape drive system, thereby providing increased storage capacity. This object is achieved by providing tape-heads having increased structural integrity and/or decreased errors in positioning. Manufacturing advantages can also be achieved with the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is perspective view of the components of an unfinished prior art tape-head assembly. 
     FIG. 2 is a perspective view of the prior art tape-head assembly of FIG. 1, as finished. 
     FIG. 3 is a perspective view of some components of an unfinished tape-head assembly of the current invention. 
     FIG. 4 is a perspective view of the tape-head assembly of FIG. 3, as finished. 
     FIG. 5 is a perspective view of some components of a second embodiment of the current invention. 
     FIG. 6 is a perspective view of some components of a third embodiment of the current invention. 
     FIG. 7 is a perspective view of some components of a fourth embodiment of the current invention. 
     FIG. 8 is a view of a media-facing side of the tape-head assembly of FIG. 4 connected to a flexible cable containing conductive leads. 
     FIG. 9 is a side view of the tape-head assembly and flexible cable of FIG. 8, mounted on an arm for positioning the assembly adjacent a tape. 
     FIG. 10 is a view of a media-facing side of the tape-head-arm assembly of FIG. 9, including a second tape-head also mounted on the arm for use in a tape drive. 
     FIG. 11 is a view of the flexible cable and tape-head-arm assembly of FIG. 10 interacting with a section of tape winding over rollers. 
     FIG. 12 is an opened up plan view of a tape drive containing the tape-head-arm assembly and tape of FIG. 11 winding over rollers between reels. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 3, some components  50  of an unfinished tape-head assembly of the current invention are shown. Much as described above, a number of microscopic transducers  52  have been formed along a surface  54  of a substrate  55  that has been covered with a cover bar or head cap  57 . The transducers  52  along surface  54  are used for reading and writing on the multiple tracks of the tape, not shown, the number of transducers preferably ranging between two and sixteen, although more or less are possible. Each of the transducers  52  may contain a magnetoresistive read element as well as an inductive write element. A pair of wear bars  61  and  63  are positioned adjacent ends of the joined substrate  55 , transducers  52  and cover bar  57 , to which the wear bars are to be bonded. The wear bars  61  and  63  have a tapered edges  66  and  68  adjacent the substrate  55  and cover bar  57 , providing greatly reduced area of faces  70  and  72  for bonding. This reduced area of faces  70  and  72  allows bonds with those faces to be thinner and more exact, reducing errors in positioning of the transducers  52 . The tapered edges  66  and  68  provide increased access for material that may be used in that bonding. 
     After bonding of the thin faces  70  and  72  to the substrate  55  and cover bar  57 , a tie bar  77  is attached to the cover bar  57  and wear bars  61  and  63 . The joined tie bar  77 , wear bars  61  and  63  and substrate  55  are then bonded with a bed  75  to form the integrated structure shown in FIG.  4 . An aperture  74  in the bed  75  allows for insertion of a flex-cable, not shown in this figure, containing leads connecting to transducers  52  along surface  54 . 
     A pair of rails  78  and  79  are formed on a transducing, tape-facing surface  76  of an assembly  80  formed from the components  20  of FIG. 3, with the transducers  52  disposed atop rail  78 . As illustrated in FIG. 11, rails  78  and  79  project from the tape-facing surface to press against the tape, which curves around the rails, so that the transducers  52  remain close to the tape for high resolution. Forming rail  79  on the tie bar  77  instead of the cover bar  57  avoids damage and misalignment of the cover bar and provides a jointless structure for the rail. 
     Attachment of the tie bar  77  provides increased strength and accuracy in a number of ways. First, the tensile and compressive strength along the length of the tie bar  77  improves lateral positioning accuracy of the transducers  52  relative to a tape that is flowing past. This improved lateral accuracy increases correspondence between the transducers and each track they communicate with, improving on-track performance. Increased on-track performance allows track and transducer widths to be decreased, increasing storage density across the width of a tape. The attachment of the tie bar  77  to the cover bar  57  also reduces the ability of the cover bar to move toward or away from the tape. Since the cover bar  57  is bonded to the transducers  52 , this improved perpendicular resilience of the assembly  80  reduces motion such as vibrations of the cover bar and transducers  52  toward and away from the tape, maintaining a more uniform proximity of the transducers  52  to the tape. Increased perpendicular stiffness can increase resolution of and/or decrease the length of each recorded bit along the tape, thereby increasing linear density. Similarly, the tie bar  77  provides increased longitudinal resilience of the assembly  80  to the longitudinal travel of the tape, which combats friction from the tape that can tug on the rails  78  and  79  with a varying force. This longitudinal stiffness can also increase transducer resolution of and/or decrease the length of each recorded bit along the tape, thereby increasing linear density. 
     The combination of increased lateral, longitudinal and perpendicular resilience of the present invention affords increased density in both track width and length directions, which provides greatly increased areal storage density. Moreover, due to the multiple means of improved resilience to vibration and other submicron movements, tape speed and therefore access time and storage capacity per unit of time can be increased. Decreasing such micromechanical movement and errors in positioning also decreases pockets and voids that can otherwise inadvertently occur, the pockets typically filling with contaminants that erode the tape and reduce the drive lifetime. 
     FIG. 5 shows some components  100  of another embodiment of the present invention, including multiple transducers  102  formed on a surface  104  of a substrate  105 , with the transducers covered by a cover bar  107 . An integrated support or tie bar  110 , which serves similar functions as the bonded wear bars and tie bar of the previous embodiment, is fitted around and attached to the substrate  105  and cover bar  107 . The bonded tie bar  110 , substrate  105  and cover bar  107  are fitted into and bonded to a bed  115 , and then rails are formed much as in the previous embodiment for use in a tape drive system. 
     FIG. 6 shows some components  150  of yet another embodiment of the present invention, which again has a number of transducers  152  formed on a surface of a substrate  155 , with the transducers covered by a cover bar  157 . A pair of wear bars  160  and  162  are bonded to the cover bar  157 , and a spacer bar  166  is bonded to the cover bar  157  and wear bars  160  and  162 . A base bar  168  is bonded to the substrate  155 , wear bars  160  and  162  and spacer bar  166 , locking the components  150  into place, after which rails are formed as described above. 
     FIG. 7 shows some components  170  of a similar embodiment to that illustrated in FIG. 6, which again has a number of transducers  172  formed on a surface of a substrate  175 , with the transducers covered by a cover bar  177 . A pair of wear bars  180  and  182  are bonded to the cover bar  177 , and a spacer bar  186  is bonded to the cover bar  177  and wear bars  180  and  182 . A base bar  188  is bonded to the substrate  175 , wear bars  180  and  182  and spacer bar  186 , locking the components  170  into place, after which rails are formed as described above. 
     The various bars described above are preferably made of ceramic materials such as Al 2 O 3 —TiC, while bed  75  is preferably made of a machinable or moldable ceramic having a thermal coefficient of expansion close to that of Al 2 O 3 —TiC. A currently preferred ceramic for use in bed  75  is sold under the trademark Macor by Accuratus Ceramic Corporation of Washington, New Jersey and includes, in decreasing amounts, silicon, magnesium, aluminum, potassium, boron and fluorine. The bonding of the components may be accomplished with an epoxy glue, although other known bonding methods are also possible. 
     All of the embodiments described above allow several ceramic and/or metal components to be bonded together into a structure having a greater bond strength and improved bond line reliability. The present invention also conserves expensive substrate and transducer real estate, while the components fit together in a manner lowering manufacturing costs and improving alignment. Once the components are bonded together, the resulting devices form a reliable foundation that minimizes submicron movements of the components. The additional support provided by these assemblies improves accuracy of lapping the transducers and machining of the rails and contouring the tape-facing surfaces, and increases coplanarity of these surfaces after such working. 
     FIG. 8 shows the tape-head assembly  80  of FIG. 4 attached to a flexible cable  200  that includes a number of conductive traces which provide electrical connections between the transducers  52  and a pair of rows of pins  205 . The pins  205  can plug into a board to provide electrical connection with the drive electronics. For the head  80  having eight read/write transducers  52 , about forty pins  205  and conductive leads are included on flexible cable  200 , the leads not shown in this figure as they would tend to confuse rather than explain the invention. The rails  78  and  79  are apparent in this view of the tape-facing side of the assembly. 
     FIG. 9 is a side view of the tape-head assembly  80  and flexible cable  200  of FIG. 7, in which the bed  75  and tie bar  77  are also apparent. A bracket or arm  222  is bonded to the bed  75 , with the cable  200  attached to the arm and bending to connect with the transducers  52 . A raised area  230  of the arm  222  provides a mount  225  for a servo mechanism  228  shown in FIG.  12  and described in detail in copending U.S. patent application Ser. No. 09/191,766, entitled Optical Apparatus for Tracking a Magnetic Tape, filed Nov. 13, 1998, and incorporated herein by reference. 
     FIG. 10 shows the head  80  and flexible cable  200  of FIG. 7 in combination with another head  210  and flexible cable  220 , the head  210  having rails  88  and  89 . The arm  222  holds the heads  80  and  210  and flexible cables  200  and  220  for positioning against a tape within a drive, not shown in this figure. A raised portion  230  of arm  222  abuts the heads  80  and  210 . The heads  80  and  210  allow the drive to read while writing without excessive noise interference. 
     FIG. 11 shows the heads  80  and  210  and flexible cables  200  and  220  of FIG. 10 engaging a tape  230  during reading and writing. The flexible cables  200  and  220  are bent in several locations, allowing rails  78 ,  79 ,  88  and  89  to be oriented toward the tape  230 . The tape  230  winds along rollers  232 ,  233 ,  234  and  235 , to arc over rails  78 ,  79 ,  88  and  89 . Arm  222  holds heads  80  and  200  and is coupled to an actuator, not shown, for moving the transducers on rails  78  and  88  to various tracks on the tape  230 . 
     The heads  80  and  210  of the present invention may be disposed in a drive  300 , such as shown in FIG.  12 . The drive  300  has a reel  305  for winding and unwinding tape  230 , and includes a cartridge  310  that contains another reel  313  and is inserted into case  315 . Rollers  232 - 235  provide a tensioned path for the tape  230  between reels  305  and  313 . The tape in this example may be hundreds of feet in length, travel at speeds of around ten feet per second and contain several hundred tracks, making accurate positioning of the heads essential. Reduction in microscopic movement and positioning errors of the heads provided by the present invention, as well as increased durability, greatly improves the performance of the drive. 
     Although we have focused on teaching the preferred embodiments, other embodiments and modifications of this invention will be apparent to persons of skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.