Abstract:
A data tape drive for recording information on the data tape of a tape cartridge has a transducer head with air bleed slots that define side walls, a tape guide, and a device for detecting damage to the transducer head and tape guide. The damage detection device has a conductor loop that is located along the outer edges of the air bleed slots and tape guide for detecting any brittle fracture damage that may be present. The conductor loop is a thin filament of wire that is preferably attached to the ends of the side walls. When the transducer head or tape guide experiences a fracture, such as a fracture in one of the side walls, the delicate filament breaks and forms an open circuit. The open circuit in the conductor loop is detected by the data tape drive so that remedial actions can be taken. Without the damage detection device, large quantities of the data tape moving past the transducer head and/or tape guide would be scraped over or gouged by the fracture and permanently damaged, including loss of the information recorded on the data tape.

Description:
This application is related to a co-pending patent application having Ser. No. 09/932,252 entitled “Apparatus for Detecting Damage to the Transducer Head and/or Tape Guide of an Interactive Media Device”, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates in general to an improved means for monitoring the physical condition of a data recording device, and in particular to an improved means for identifying damage to the components of a data recording device. Still more particularly, the present invention relates to an improved method for detecting fractures in a recording head or tape guide in a data tape drive. 
     2. Description of the Prior Art 
     Data recording devices, such as data tape drives, record information to or read information from media in a data storage device, such as the data tape of a tape cartridge. As shown in FIG. 1, data tape drives utilize one or more transducer heads  1  having air bleed grooves or slots  3  that define side walls  5 . The air bleed slots  3  are provided for optimizing the performance of the transducer head  1 . For example, U.S. Pat. No. 5,636,085 discloses a magnetic read/write assembly for a flexible disk drive having rails with air bleed slots that enable a low flying height for the media relative to the electromagnetic elements. 
     Referring again to FIG. 1, air bleed slots  3  are typically formed in the transducer head  1  in a direction that is perpendicular to the direction of travel of the tape (indicated by arrows  7 ). However, the slots also may be formed or cut in directions parallel to the direction of travel of the magnetic tape. The air bleed slots allow the tape to ride closer to the read and write elements in the head by bleeding off the boundary layer air which sticks to the moving tape. Although tape tension is used to wrap the tape over the head, high density recording requires the tape to hydrodynamically fly extremely close to the recording elements. 
     Transducer heads and the tape guides adjacent to them are typically formed from sensitive materials that are somewhat brittle in nature, and are subject to brittle fracture damage due to vibration, shock, and incidental contact with the media. When air bleed slots or other mechanical formations are formed in transducer heads and tape guides, areas of stress concentration occur and may increase the likelihood of damage to these components. The side walls of the transducer head are particularly vulnerable to stress concentrations and fractures. When a transducer head or tape guide is damaged, the media or data tape may be exposed to the sharp edges  9  (FIG. 1) of the fracture. Unless the situation is quickly remedied, extensive amounts of the media can be damaged or destroyed, and valuable information can be permanently lost. Thus, a method for detecting damage to the transducer head and tape guide of a data recording device is needed. 
     SUMMARY OF THE INVENTION 
     A data tape drive for recording information on the data tape of a tape cartridge has a transducer head with air bleed slots that define side walls, a tape guide, and a device for detecting damage to the transducer head and tape guide. The damage detection device has a conductor loop that is located along the outer edges of the air bleed slots and tape guide for detecting any brittle fracture damage that may be present. The conductor loop is a thin filament of wire that is preferably attached to the ends of the side walls. Alternatively, the filament is mounted along the side walls just below the top surface of the side walls to avoid contact with the moving data tape during operation of the data tape drive. When the transducer head or tape guide experiences a fracture, such as a fracture in one of the side walls, the delicate filament breaks and forms an open circuit. The open circuit in the conductor loop is detected by the data tape drive so that remedial actions can be taken. Without the damage detection device, large quantities of the data tape moving past the transducer head and/or tape guide would be scraped over or gouged by the fracture and permanently damaged, including loss of the information recorded on the data tape. 
    
    
     The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 
     DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
     FIG. 1 is a top view of a prior art transducer head that has fractured. 
     FIG. 2 is an exploded isometric view of a magnetic tape drive constructed in accordance with the invention. 
     FIG. 3 is an isometric view of the tape drive of FIG. 2 to be mounted on a chassis having shock mounts for isolation therebetween. 
     FIG. 4 is an isometric view of a head guide assembly of the tape drive of FIG. 2 having a head actuator assembly mounted therein. 
     FIG. 5 is a schematic diagram of the tape drive of FIG. 2 having a transducer head and tape guide constructed in accordance with the invention. 
     FIG. 6 is an enlarged front view of a portion of the tape guide of FIG.  5 . 
     FIG. 7 is a schematic sectional side view of the tape guide of FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 2, a magnetic tape drive  11  in which the present invention may be incorporated is shown. Although a magnetic tape drive is illustrated, one skilled in the art will recognize that air bearing sliders on the magnetic heads used in disk drives with removable media, an optical media drive, such as a CD-ROM device, a Near Field Recording device that combines magnetic and optical recording, or other devices having transducer heads for processing information with media, such as reading information from and/or writing information to media, also may employ the present invention. Drive  11  includes a base unit  13  to which are mounted a power supply  15 , various electronic circuit cards  17 ,  19  (such as motion control and data control), a deck assembly  21 , a pneumatic assembly  23  that provides pressurized air, and tape tension transducer  201  that measures the tension in the data tape and feeds back that information to cards  17 ,  19 . Mounted to the deck assembly  21  are a loader mechanism  27 , drive motors (not shown), a pantocam assembly  29 , and a head guide assembly  31 . A head actuator assembly  33  is mounted to the head guide assembly  31 . Drive  11  can operate in stand alone and automated tape loader environments interconnected with a host computer and also can be incorporated into a multi-drive automated data storage and retrieval system or library. 
     As shown in FIG. 3, shock mounts  35  are supported by the base unit  13  for isolating the deck assembly  21  from shock. Shock mounts  35  are stud-mounted-type shock mounts for assembly ease. Four shock mounts  35  (only two are shown) are positioned approximately equidistant from the center of gravity of deck assembly  21 . 
     Referring now to FIG. 4, actuator assembly  33  of head guide assembly  31  is secured to a base member  41 . Base member  41  is coupled to a head guide support  43 . Various brackets and screws secure the elements of the actuator assembly  33  together. Various cables, including ribbon cables  45  for the transducer or input/output recording head  47 , interconnect the head and the coil with the circuit cards of drive  11 . To reduce mechanical interference by ribbon cables  45  with proper motion of a beam member, ribbon cables  45  are preferably guided upwards along the sides of the beam member and outwardly from the base member  41  by winged surfaces inside the beam member. Head  47  may comprise a device that is read only, write-once, or one that can perform both read and write functions. 
     An arcuate tape guide  40  is located immediately adjacent to each side of head  47  for precisely conveying data tape toward and away from head  47 . In the embodiment shown, an alumina ceramic, flat plate-like tape guide  40  is supported from above by D-bearings  42  and from below by lower support members  44  that are spaced apart from each other to provide a slot for tape guide  40 . As best shown in FIG. 5, tape guide  40  has a row of teeth  46  that define the arcuate guide path for the data tape, locating pin slots or holes  48 , mounting bolt holes  52 , and an air vent  54  for hydrostatic air delivered to the head guide assembly  31 . A more detailed disclosure of drive  11  is shown and described in U.S. Pat. Nos. 5,508,865, and 5,377,052, which are incorporated herein by reference. 
     During operation of drive  11 , a removable tape cartridge  37  (FIG. 2) having a supply reel wound with magnetic tape is inserted through a slot  39  in a front face of base unit  13 , and into loader assembly  27 . A warning indicator  38  is located adjacent to slot  39  and will be described in further detail below. Loader assembly  27  draws the tape cartridge  37  in and lowers it onto the deck assembly  21 . The pantocam assembly  29  engages the tape leader block attached to a free end of the magnetic tape and pulls the magnetic tape around the head guide assembly  31  such that the magnetic tape winds through the tape path defined by tape guide  40 , and across the magnetic tape head  47  mounted to the head actuator assembly  33 . The leader block is then engaged by a take-up reel  200  on the deck assembly  21  and drive  11  is then ready to record information to or read information from the magnetic tape. While drive  11  includes a take-up reel and accepts tape cartridges containing only the supply reel, the present invention is not limited to use with such a drive or cartridge combination, but also could be incorporated in other drive or cartridge combinations, such as those in which the tape cartridge contains both supply and take-up reels. A two-reel tape cartridge is also called a dual-reel cassette. 
     Referring again to FIG. 4, a solenoid  101  controls the flow of pressurized air through a hose  102  to head  47 . Head  47  has an orifice  103  that is typically located between or to the sides of columns of I/O elements  104 ,  105 . The data tape normally flies over I/O elements  104 ,  105  via a hydrodynamic air film  109  (see FIG.  5 ). A hydrodynamic air film is preferred for a good head, because hydrodynamic air films are very thin. A thin hydrodynamic air film allows the data tape  51  to fly very close to I/O elements  104 ,  105 , which allows the transfer of data between tape  51  and the I/O elements of head  47 . The thickness of a hydrodynamic air film is a few microinches. 
     Tape  51  also flies over D-bearings  42  via a very thick hydrostatic air film  99 . Hydrostatic air films are typically orders of magnitude thicker than hydrodynamic air films (in the range of the thickness of tape  51 ), which is a few thousandths of an inch rather than mere microinches. Since tape  51  should not physically contact D-bearings  42 , and since D-bearings  42  only facilitate the guiding of tape  51  over head  47 , a thick layer of hydrostatic air between tape  51  and D-bearings  42  is desirable, especially in the event that head  47  fractures. 
     Referring again to FIG. 5, a schematic diagram of a portion of drive  11 , tape guide  40 , and transducer head  47  constructed in accordance with the present invention is shown. A plurality of air bleed slots  49  that define side walls  50  are formed in the ferrite block or base comprising head  47 , along with the input/output elements. Magnetic tape  51  passes in a generally arcuate path over head  47  and slots  49  in the directions of travel indicated by arrows  53 . Head  47  is also provided with a delicate or brittle electrically conductive means or a conductor loop  55 . In one version, conductor loop  55  extends along the perimeter of head  47 , and preferably comprises a thin film conductor or wire that is laminated to the top and bottom surfaces of head  47 . Alternatively, conductor loop  55  is mounted along sides of head  47  just below an outer or tape surface  57  thereof to avoid contact with tape  51  while the tape is moving during operation of drive  11 . 
     As shown in FIGS. 5 and 6, the curved array of teeth  46  in tape guide  40  define grooves  56  therebetween, and each tooth  46  has a tape surface  60  that is essentially perpendicular to tape  51 . Like head  47 , tape guide  40  is provided with a conductor loop  58  that extends along the perimeters of tape guide  40  and teeth  46 . In one version, loop  58  comprises a thin film conductor or wire that is laminated to tape surface  60  of tape guide  40  (FIGS.  5  and  6 ). In this version, loop  58  is mounted along tape surface  60  to avoid contact with tape  51  while the tape is moving during operation of drive  11 . However, loop  58  is preferably located on the opposite side of tape surface  60 . 
     Referring now to FIG. 7, the face of D-bearing  42  is a portion of a right circular cylinder. D-bearing  42  accepts pressurized air through hole  54 , as provided by pneumatic assembly  23 , and vents the pressurized air through holes  98  (approximately 0.010 inches in diameter) to form the hydrostatic air film or bearing  99 , which supports tape  51 . The pressure of hydrostatic film  99  is described by the expression P= T/RW, wherein T is the tension of tape  51  as measured by tension transducer  201  (FIG.  2 ), R is the outer radius of D-bearing  42 , and W is the width of tape  51 . The gaps  56  (FIG. 5) between teeth  46  of tape guide  40  vent hydrostatic air film  99 . If hydrostatic air film  99  is not vented along the lower edge of tape  51 , hydrostatic air film  99  will collapse and form a tension gradient in tape  51  across the width of tape  51 . Ceramic plugs  93  are located along the top edge of tape  51  and only act on the edge of tape  51  in a few places, but do not seal the upper edge of tape  51 . Thus, the upper edge of tape  51  is self-venting and the lower edge of tape  51  needs venting of the gaps  56  between teeth  46 . Offset block  91  is used to mount a leaf spring  92 , to which ceramic plug  93  is attached. 
     When a fracture in the side walls forming the air bleed slots  49  of head  47 , or in the teeth  46  of tape guide  40  occurs, an open circuit is produced in conductor loops  55 ,  58 , respectively. Drive  11  is provided with a circuit  61  that senses the open circuit in either or both conductor loops  55 ,  58 . For example, in the embodiment shown, circuit  61  is provided with resistors  62 ,  64 ,  66  a transistor  68 , and a threshold comparator  63  for sensing when loops  55 ,  58  are opened or fractured. In the preferred embodiment, transistor  68  is an NPN switching transistor 2N2222, beta˜100, and comparator  63  is an LM 139 . Threshold comparator  63  compares a change in voltage of circuit  61  to a threshold voltage, Vref, which is preferably 2.5 volts. If the circuit voltage is higher than Vref, the circuit voltage is assumed to be “high” (e.g., at least one of conductor loops  55 ,  58  has fractured along with its underlying structure, and its respective head  47  and/or tape guide  40  is damaged), and the output Vout of comparator  63  is a digital  1 . If the circuit voltage is lower than Vref, the circuit voltage is assumed to be “low” (head  47  and tape guide  40  are in an acceptable condition), and the output of comparator  63  is a digital  0 . In the latter case, drive  11  operates as normal. However, in the former case, drive  11  senses the change and stops running tape  51 , which prevents further input and/or output, so that an extensive amount of tape  51  is not ruined by the sharp fractured edges of what remains of head  47  and/or tape guide  50 . 
     In response to the disruption in service, drive  11  signals an operator or requests maintenance so that the damaged head or tape guide can be replaced with a new one. 
     In one version of the invention, warning indicator  38  (FIG. 2) is activated to warn the user to not load media, such as tape cartridge  37 , in slot  39 . Moreover, loader  27  may be equipped to refuse to load media once either of loops  55 ,  58  are open and comparator  63  is a digital  1 , indicating that either tape guide  40  or head  47  is damaged. 
     In another version of the invention, drive  11  communicates with, for example, a repair center or maintenance facility  67  via communications equipment  65  when comparator  63  yields a “1.” Communications equipment  65  may comprise a wired or wireless transmission via a telephone, a modem for a telephone, a local area network, the internet, etc., for communicating with the repair center. 
     Drive  11  is also has an Emergency Recovery Procedure (ERP). When broken conductor loop  55  is detected, a pneumatic lifter, as taught by U.S. Pat. No. 4,479,158 (incorporated herein by reference), is engaged to push or lift tape  51  away from the broken head  47 . When circuit  61  detects a fractured head (see FIG.  1 ), solenoid  101  (FIG. 4) is engaged to pass the same pressurized air that is being sent to D-bearings  42 , to head  47  via hose  102 . This pressurized air vents via orifice  103  underneath tape  51 , and pushes or lifts tape  51  away from the damaged head  47  so that tape  51  is not damaged by the sharp fractures  9  shown in FIG.  1 . In addition, the tension in tape  51  is reduced, which allows the pneumatic lifter to further lift tape  51  away from broken head  47 . The ERP reduces the chance of ruining tape  51 , and may be used in conjunction with warning indicator  38  and the communication with repair center or maintenance facility  67 . 
     The present invention has several advantages. The damage detection device prevents large quantities of data tape from being damaged by a fractured recording head or tape guide. The damage detection device signals the data tape drive to stop using the damaged component, to alert an operator, or other remedial actions to prevent extensive damage to the data tape. The conductor loops utilized by the damage detection device may be attached to the ends of the side walls, or mounted along the side walls just below the top surface of the side walls to avoid contact with the moving data tape during operation of the data tape drive. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, the present invention also applies to optical tape.