Abstract:
A magnetic recording head according to one embodiment comprises a support having a surface with an opening in said surface; at least one head chin comprising a substrate having a plurality of magnetic recording elements, said head chip positioned to protrude through the opening in the surface of the support for read/write access to a magnetic recording tape, a tape bearing surface of the head chip being positioned above the surface of the support, wherein the at least one head chip includes two transducing surfaces separated in a direction parallel to a direction of tape travel over the at least one head chip by a gap and held in fixed relation to one another. Additional embodiments are also presented.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 11/426,558, filed Jun. 26, 2006, now U.S. Pat. No. 7,382,581, which is a continuation of U.S. patent application Ser. No. 10/738,385, filed Dec. 17, 2003 and now U.S. Pat. No. 7,133,261. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to magnetic tape recording heads, and more particularly to a tape recording head with a support plate having a contoured surface to support the recording tape passing over the recording head. 
   2. Description of the Related Art 
   In magnetic storage systems, data is read from and written onto magnetic recording media utilizing magnetic transducers commonly referred to as magnetic heads. Data is written on the magnetic recording media by moving a magnetic recording head to a position over the media where the data is to be stored. The magnetic recording head then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read head and then sensing the magnetic field of the magnetic media. Read and write operations are independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media. 
   An important and continuing goal in the data storage industry is that of increasing the density of data stored on a medium. For tape storage systems, that goal has lead to increasing the track density on recording tape, and decreasing the thickness of the magnetic tape medium. However, the development of small footprint, higher performance tape drive systems has created various problems in the design of a tape head assembly for use in such systems. 
   In a tape drive system, magnetic tape is moved over the surface of the tape head at high speed. This movement generally entrains a film of air between the head and tape. Usually the tape head is designed to minimize the spacing between the head and the tape. The spacing between the magnetic head and the magnetic tape is crucial so that the recording gaps of the transducers, which are the source of the magnetic recording flux, are in intimate or near contact with the tape to effect efficient signal transfer, and so that the read element, is in intimate or near contact with the tape to provide effective coupling of the magnetic field from the tape to the read element. The conventional head contour comprises a cylindrical or complex shape which is critical in maintaining the moving tape at the desired spacing from the head. The contact, or near contact, spacing is maintained by controlling the contour shape to “bleed”, or scrape the boundary layer of air carried by the tape away and into bleed slots before encountering the transducer to prevent, the tape from “flying”, or losing contact with the transducer. 
   Alternatively, the contour is designed with a small radios and a high wrap angle so that high pressure is exerted on the head while the tension is low. However, the contour of the head roust be such that the pressure exerted by the tape on the transducer is not so high that the surface of the transducer wears excessively. Heads are often provided with outriggers on both sides of the head which help support the tape and reduce head wear, but, more importantly, control the wrap angle of the tape with respect to the head. Any change in radius will change the pressure of the tape on the head at the same tape tension. 
   A flat contour thin film tape recording head for a bi-directional tape drive has been described in U.S. Pat. No. 5,905,613. The flat contour head comprises a flat transducing surface on a substrate having a row of thin film transducers formed on a surface on one side of the substrate which forms a gap. The substrate with the row of transducers is called a “rowbar substrate”. The transducers are protected by a closure of the same or similar ceramic as the substrate. For a read-while-write bi-directional head which requires that the read transducer follows behind the write transducer, two rowbar substrates with closures are mounted in a carrier facing one another. The recording tape overwraps the corners of both substrates with an angle sufficient to scrape the air from the surface of the tape and not so large as to allow air to reenter between the tape and the transducing surface after the tape passes the corner. By scraping the air from the surface of the moving tape, a vacuum forms between the tape and the flat transducing surface holding the tape in contact with the transducing surface. At the corners of the substrates, bending of the recording tape due to the overwrap results in separation of the tape from the transducing surface for a distance that depends on the wrap angle, the tape thickness and the tape tension. The transducers must be spaced from the corners of the substrate at a sufficient distance to allow the vacuum between the tape and the transducing surface to overcome this separation. 
   There is an ongoing need for reduced separation of the transducers and the recording media and of improved control and reliability of this separation in order to support constantly increasing data density and speed requirements of data storage systems. The present invention provides an improved recording head to address this need. 
   SUMMARY OF THE INVENTION 
   A magnetic recording head according to one embodiment comprises a support having a surface with an opening in said surface; at least one head chip comprising a substrate having a plurality of magnetic recording elements, said head chip positioned to protrude through the opening in the surface of the support for read/write access to a magnetic recording tape, a tape bearing surface of the head chip being positioned above the surface of the support, wherein the at least one head chip includes two transducing surfaces separated in a direction parallel to a direction of tape travel over the at least one head chip by a gap and held in fixed relation to one another. 
   A magnetic recording head according to another embodiment comprises a support having a contoured surface with an opening in said contoured surface; and at least one head chip comprising a substrate having a plurality of magnetic recording elements, said head chip positioned to protrude through the opening in the contoured surface of the support for read/write access to a magnetic recording tape, wherein the head chip is moveable relative to the support in a direction perpendicular to the direction of tape motion over the contoured surface. 
   A method according to another embodiment comprises, using a coarse actuator, moving a support having a contoured surface with an opening in said contoured surface, wherein at least one head chip comprising a substrate having a plurality of magnetic recording elements is positioned to protrude through the opening in the contoured surface of the support for read/write access to a magnetic recording tape; and using a fine actuator, moving the head chip relative to the support in a direction perpendicular to the direction of tape motion over the contoured surface. 
   The above as well as additional objects, features, embodiments and advantages of the present invention will become apparent in the following detailed description. 
   The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings. In the following drawings, like reference numerals designate like or similar parts throughout the drawings. 
       FIG. 1  is a perspective illustration, not to scale, of a first embodiment of a tape recording head of the present, invention. 
       FIG. 2  is an end view illustration, not to scale, of the embodiment of the tape recording head shown in  FIG. 1 . 
       FIG. 3  is an end view section, not to scale, of the head chips and carrier portion of a first embodiment of the tape recording head shown in  FIGS. 1 and 2 . 
       FIG. 4  is a simplified diagram of a magnetic tape recorder system using the magnetic recording head of the present invention. 
       FIG. 5  is an end view section, not to scale, of the head chips and earner portion of a second embodiment of the tape recording head. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a perspective view, not to scale, of a first embodiment of the tape recording head  100  of the present invention.  FIG. 2  shows an end view, not to scale, of the tape recording head  100 . Referring to  FIGS. 1 and 2 , the tape recording head  100  comprises a support plate  102  having a cylindrical contoured surface  104  with a rectangular opening  106  which allows head chips  108  to protrude far enough to allow proper head tape contact for recording. The cylindrical contoured surface  104  has a substantially rectangular shape. The support plate  102  is fixed by supports  112  on a base carrier  110  that is rigidly mounted on a coarse actuator  111  so that the support plate  102  and coarse actuator move together in a direction perpendicular to the direction of the linear motion  115  of recording tape  114  (shown in phantom) over recording head  100 . The head chips  108  comprising rowbar substrates  116  containing a multiplicity of recording transducers are supported on a carrier  118  mounted on a fine actuator  119  and are not fixed to the support plate  102  to allow low-mass, high bandwidth fine actuation relative to the recording tape  114  as indicated by the arrow  120 . Electrical connection cables  117  connect the transducers on the head chips  108  to the read/write channel of the associated tape drive. 
     FIG. 3  shows an end view section, not to scale, of the head chips  108  and carrier  118  portion of the tape recording head  100  of  FIGS. 1 and 2 . The head chip  108  is a bi-directional read-while-write head similar to tape recording heads described, in U.S. Pat. No. 5,905,613 which discloses a flat, contour linear tape recording head and U.S. Pat. No. 5,883,770 which discloses a partial width linear tape recording head. The head chip  108  comprises rowbar substrates  116  of a wear resistant material, such as the substrate ceramic typically used in magnetic disk drive heads, fixed on a carrier  118  mounted on a fine actuator means  119 . The ceramic rowbar substrates  116  are provided with transducing surfaces  302  and a row of transducers on the surfaces of gaps  304 . Electrical connection cables  117  connect the transducers to the read/write channel of the associated tape drive. The rows of transducers are protected by closures  308  made of the same or similar ceramic as the rowbar substrates  116 . The transducing surfaces  302  of the rowbar substrates  116  are designed to protrude a distance d above the cylindrical surface  104  of the support plate  102  when assembled in the tape recording head  100  of  FIGS. 1 and 2  to allow proper contact with the recording tape  114 . The protrusion distance d of the transducing surfaces  302  is typically in the range of 5-25 microns. The protrusion distance d determines the wrap angle h of the tape  114  at the edge of the transducing surface  302 . Because of the protrusion of the transducing surfaces above the cylindrical, surface of the support plate, the tape to usually does not contact the edge of the rectangular opening  106  of the support plate. 
   The support plate  102  is fabricated to have a cylindrical surface  104  having a polished surface finish. If desired, the polished surface may include microgrooves or other surface texture for controlling sticking in humid environments when the tape is at rest. During operation, the recording tape  114  normally flies over the cylindrical surface  104  with a separation or fly height in the range of approximately 1-5 microns depending on the tape, tape velocity and radius. A radius R of 33 mm for cylindrical surface  104  was used to give the desired performance for a minimum fly height flat head. However, a radius R in the range of 10-100 mm may be used for various recording head designs and applications. The rectangular opening  106  is formed by molding or, alternatively, by a suitable machining process to have dimensions slightly greater than the head chip  108  dimensions to allow for fine actuation movement of the a head without interference from the support plate  102 . The dimension of the support plate in the direction perpendicular to the direction of tape motion is preferably chosen to support the tape over the full range of actuation of the tape recording head. The thickness of the support plate is chosen to be sufficient to provide the desired strength and rigidity. Typically, the support plate  102  is aligned to the head chips  108  after the head and actuator are assembled. The support plate position is controlled to typically +/−2 microns relative to the head chips for proper operation. The support plate is formed of a hard ceramic, such as Al—Ti—C, or of a hardened metallic alloy. Alternatively, the support plate may be formed of a metal, ceramic or plastic material coated with a hard wear layer such as, for example, Si—N to provide wear resistance at possible areas of contact with the tape at the tape edges and near the opening  106  in the support plate. The support plate is preferably static dissipative, or conductive and grounded or held at an appropriate bias potential to avoid electrostatic charge buildup. 
   One embodiment of the magnetic recording head  100  of the present invention comprises a support plate  102  having a cylindrical contoured surface  104  with a substantially rectangular opening  106  in the surface to allow head chips  108  to protrude. Alternatively, support plates having other contoured surfaces may be used. For example, the cylindrical contoured surface  104  having a constant radius of curvature R in the direction of linear motion  115  of the tape as shown in  FIG. 2  may be modified to have a smoothly varying radius of curvature in going from the left side to the midpoint and from the midpoint to the right side of the support plate shown in  FIG. 2 . A large radius of curvature at the left edge of the support plate changing to a smaller radius of curvature at the midpoint of the support plate and changing back to a large radius of curvature at the right edge of the support plate would be one of many possibilities that may be advantageous. Slight contouring of the support plate in the direction perpendicular to the direction of linear motion  115  of the tape relative to the magnetic recording head can also be used and may be advantageous in improving stability of the tape relative to the recording head. Similarly, alternative shapes of the opening  106  may be used to better match the shape of the particular head chips being used. For example, a circular or substantially circular opening may be appropriate for a circular button-shaped head chip design. In the first embodiment, the opening  106  is approximately centered in the contoured surface  104  of the support plate  102 . Alternatively, the opening may be offset from the center of the support plate. The contoured surface of the support plate may have shapes other than the substantially rectangular shape of the embodiment illustrated in  FIG. 1 . The contoured surface may, for example, have a square shape or may be circular or oval in shape in other embodiments. 
   The embodiment illustrated in  FIGS. 1-3  has transducing surfaces  302  that are flat and lie in a common plane. Alternatively, the transducing surfaces  302  of the two rowbar substrates  116  to may be contoured or may be tilted at a small angle with respect to one another. 
   Coarse and fine actuation for positioning the magnetic tape recording head perpendicular to the direction of tape motion over the head may be implemented by a number of actuator means known to the art including among others electric motor driven lag screws, electromagnetic induction drives (voice coil drives) and piezoelectric devices. Electric motor driven lag screw devices and voice coil drives are most suitable for use in coarse actuator devices moving relatively large masses over relatively long distances. Micro electromagnetic induction drives and piezoelectric devices are suitable for fine actuator devices moving small masses over small distances with high bandwidth performance. 
     FIG. 5  shows a second embodiment of a tape recording head  500  according to the present invention. Tape recording head  500  differs from the tape recording head  100  shown in  FIGS. 1-3  in having the support plate  102  fixed by supports  512  on the carrier  118  instead of being fixed by supports  112  on the base carrier  110 . Fixing the support plate  102  on the carrier  118  results in having the support plate  102  and the head chips  108  moving together with movement of the fine actuator  119 . In all other respects, the tape recording head  500  of the second embodiment is the same as the tape recording head  100  of the first embodiment. In this embodiment the mass of the support plate  102  adds to the total mass that has to be moved by the fine actuator which to a degree degrades the high frequency performance of the fine actuation means. However, fixing the support plate to the carrier simplifies alignment of the support plate to the head chips. 
     FIG. 4  illustrates an embodiment of a magnetic tape recorder or tape drive system  400  incorporating the tape recording head of the present invention. A tape drive control unit  402  provides a motor control signal to rotate tape reels  404  and move magnetic tape  406  across the read/write transducer head  401 . Read/write channel  408  transmits read/write signals between the read/write transducer  401  and the control unit  402 . The data is communicated through I/O channel  410  with host  412 . Lateral positioning of the transducer  401  with respect to the tape  406  is accomplished by coarse and fine positioning actuators  414 . The lateral repositioning by a coarse actuator is required to access the various tracks of the tape  406  with the transducer  401 . A servo system and fine actuator may be employed for accurate lateral repositioning of the transducer  401 . An exemplary servo system includes a servo detector  416  to detect both the track that the head is currently on and whether the head is off center. Control unit  402  indicates the track address of a desired new track to position error detection controller  418  for repositioning the head. Servo detector  416  indicates the current track to position error detection controller  418 , and the controller provides a servo position error signal to the coarse actuator of positioning actuators  414  which repositions the transducer  401  to the new track. The servo system also provides track following signals to the fine actuator of positioning actuators  414  so that the tracks on tape  406  may be closely spaced. 
   While the present invention has been particularly shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit scope and teaching of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited only as specified in the appended claims.