Patent Publication Number: US-2009225462-A1

Title: Magnetic tape device

Description:
This application is based upon and claims the benefit of priority from Japanese patent application No. 2008-052764, filed Mar. 4, 2008, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic tape device for recording and reproducing data on magnetic tape. 
     2. Background of the Invention 
     Magnetic tape devices employing magnetic tape as a storage medium have recently been developed as external storage devices for computers. When a magnetic tape device performs data recording or reproduction processing, magnetic tape runs in contact with a magnetic head. When the recording or reproduction processing is suspended, the magnetic tape remains in contact with the magnetic head. If the magnetic tape stays in this state for a prolonged time, the magnetic tape is possibly stuck on the magnetic head. Therefore, there are demands for countermeasures against this problem. 
     In order to improve the contact between magnetic tape and a magnetic head, an air escape groove may be provided in the surface of the magnetic head which comes into contact with the magnetic tape. However, the shape of this grove is possibly transferred to the magnetic tape to cause irregularity of the surface of the magnetic tape. This irregularity may result in an error in recording or reproducing data. Therefore, countermeasures against this problem are also demanded. 
     As one of countermeasures against these problems, there has been proposed a related art for preventing magnetic tape from being stuck on a magnetic head and preventing the shape of groove from being transferred to the magnetic tape. According to this related art, a gap is formed in a central portion of the magnetic head, and air is blown to the magnetic tape from this gap with the use of an air pump to thereby avoid the direct contact between the magnetic tape and the magnetic head. 
     Another related art is also proposed, according to which magnetic tape is caused to run in a reciprocating manner over a minute distance during the idle period in which the magnetic head is not performing recording or reproducing operation. 
     However, the former related art requires an air pump which is expensive and large in size, in order to avoid the direct contact between the magnetic tape and the magnetic head. Thus, this method has a problem that it is difficult to reduce the size and cost of the magnetic tape device. 
     In the latter related art, the magnetic tape runs in a reciprocating manner over a minute distance typically at predetermined intervals. Since these intervals are set to a fixed value regardless of temperature within the magnetic tape device, problems as follows are posed. Specifically, magnetic tape is more apt to stick to the magnetic head as the temperature becomes higher. If the intervals mentioned above are set to an unduly low value even though the temperature is low, the magnetic tape will be damaged by the reciprocating running. In contrast, if the intervals are set to a high value even though the temperature is high, the magnetic tape cannot be prevented from being stuck to the magnetic head. 
     In order to solve these problems: Japanese Laid-Open Patent Publication No. H08-96438 (Patent Document 1) proposes a magnetic tape device which is suitable for reducing the size and cost the device and is adapted to detect the temperature within the device for preventing magnetic tape from being stuck to the magnetic head, in a desirable manner. 
     SUMMARY OF THE INVENTION 
     However, according to Patent Document 1, in order to desirably prevent the magnetic tape from being stuck to the magnetic head, the temperature within the magnetic tape device is detected by a temperature sensor arranged near the magnetic head within the magnetic tape device, and an operation to eliminate the sticking of the magnetic tape to the magnetic head is performed once the detected temperature exceeds a predetermined value. 
     The temperature sensor described above does not directly detect the temperature of the magnetic tape and the magnetic head, but detects the temperature in the vicinity of the magnetic head so that the operation to eliminate the sticking of the magnetic tape to the magnetic head is performed once the detected temperature exceeds a reference temperature at which the sticking of the magnetic tape to the magnetic head presumably occurs. Therefore, if the reference temperature is set too low, the operation to eliminate the sticking of the magnetic tape to the magnetic head is performed even though the magnetic tape is not stuck to the magnetic head, posing a problem that the operation to eliminate the sticking is performed too often. If the reference temperature is set too high, in contrast, it takes some time to commence the operation to eliminate the sticking of the magnetic tape to the magnetic head even though the magnetic tape is stuck to the magnetic head. In addition, the technique described in Patent Document 1 has a problem that the operation to eliminate the sticking of the magnetic tape to the magnetic head can be performed only during the idle period of the magnetic tape device in which the magnetic head is not performing the recording or reproducing operation. 
     Therefore, an exemplary object of the invention is to provide a magnetic tape device which is capable of quickly starting an operation to eliminate the sticking of magnetic tape to the magnetic head only when the sticking of the magnetic tape to the magnetic head is confirmed, and thus capable of eliminating the waste and inefficiency in the operation and reducing the load to the magnetic tape. 
     A magnetic tape device according to an exemplary aspect of the invention comprises a magnetic head for recording and reproducing data on and from magnetic tape; a drive unit for running the magnetic tape in contact with the magnetic head along with the data recording or reproducing operation of the magnetic head; an abnormality detector for detecting an abnormality in operation of the magnetic tape; and a release unit for releasing forcibly the contact between the magnetic tape and the magnetic head when any abnormality is detected by the abnormality detector while the magnetic tape is running. 
     The present invention provides an advantageous effect that the operation to eliminate the sticking of the magnetic tape to the magnetic head can be quickly performed only when the sticking of the magnetic tape to the magnetic head is confirmed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a principal portion of a magnetic tape device  1  according to an embodiment of the present invention; 
         FIG. 2  is a plan view showing a state in which the sticking of magnetic tape  7  to a magnetic head  2  has been eliminated; 
         FIG. 3A  is a diagram showing a mechanism of a tape lifter  3 ; 
         FIG. 3B  is a cross-sectional view taken along line  3 B- 3 B of  FIG. 3A ; 
         FIG. 4  is a block diagram showing an example of a hardware configuration of the magnetic tape device  1 ; and 
         FIG. 5  is a flowchart showing processing to eliminate the sticking of the magnetic tape  7  to the magnetic head  2 . 
     
    
    
     EXEMPLARY EMBODIMENT 
     A most preferred exemplary embodiment will be described with reference to the accompanying drawings.  FIG. 1  is a plan view illustrating a principal portion of a magnetic tape device according to an embodiment of the present invention. As shown in  FIG. 1 , the magnetic tape device  1  comprises a magnetic head  2 , a tape lifter  3 , a roller guide  4 , a cartridge reel  5 , a machine reel flange  6 , and magnetic tape  7 . 
     Next, description will be made of how the magnetic tape  7  is run within the magnetic tape device. In the state of the magnetic tape  7  as shown in  FIG. 1 , an end of the magnetic tape  7  stored on the cartridge reel  5  is in contact with the roller guide  4  and the magnetic head  2 , and is connected to a certain part of the machine reel flange  6 . 
     The cartridge reel  5  and the machine reel flange  6  are driven separately by a reel motor  8  (not shown in  FIG. 1 ) which is an independent drive unit. Thus, the magnetic tape  7  can be run under a certain tension by driving the independent reel motor  8 , so that data can be recorded on or reproduced from the magnetic tape  7  by means of the magnetic head  2 . 
       FIG. 2  shows the state in which when the magnetic tape  7  is stuck to the magnetic head  2 , the sticking is eliminated by the tape lifter  3  functioning as a release unit. The tape lifter  3  is moved upward as viewed in  FIG. 2  (in the direction indicated by the arrow in  FIG. 2 ) to lift up the magnetic tape  7 , whereby the sticking of the magnetic tape  7  to the magnetic head  2  is eliminated. Mechanism of the tape lifter  3  will be described later in detail with reference to  FIGS. 3A and 3B . 
       FIGS. 3A and 3B  are diagrams showing a mechanism of the tape lifter  3 . When the magnetic tape  7  is stuck to the magnetic head  2 , the tape lifter  3  is driven. More specifically, a motor  35  is driven to slide a rack  36  in a part of a lifter bar  31  by means of a pinion gear (not shown) provided on the motor  35 , whereby the lifter bar  31  formed as a bar-like projection can be protruded. The tape lifter  3  comprises a flag  33  and a photo sensor  34  both attached to the lifter bar  3  in order to detect the position of the lifter bar  31  during its sliding movement. The detection of the flag  33  by the photo sensor  34  confirms that the lifter bar  31  has been protruded sufficiently so that the magnetic tape  7  is pushed up by the distal end  32  of the lifter bar  31  and the sticking of the magnetic tape  7  to the magnetic head  2  is eliminated. 
       FIG. 4  is a block diagram showing a hardware configuration of the magnetic tape device  1 . An MPU (microprocessor unit)  85  (an abnormally detector) is connected to a host computer serving as a host controller (not shown) via an interface control circuit  81 . 
     Computation results obtained using various programs are supplied from the MPU  85 , by means of electrical signals, to a recording/reproduction/deletion control circuit  82  for controlling the magnetic head  2 , a lifter drive circuit  83  for driving the tape lifter  3 , and a reel motor drive circuit  88  for driving the reel motor  8  (drive motor). In addition, a reel motor  8  and a reel motor drive circuit  88  is a component of drive unit  90 . 
     A pulse detection sensor  89  serving detects a pulse generated by the reel motor  8  and transmits the detection result to the MPU  85 . 
       FIG. 5  is a flowchart showing a series of processing steps for eliminating the sticking of the magnetic tape  7  to the magnetic head  2 . 
     First, in step S 101 , the MPU  85  transmit electrical signals instructing to drive the reel motor  8  to the reel motor drive circuit  88 . 
     The MPU  85  also transmit electrical signals instructing to load magnetic tape  7  to the recording/reproduction/deletion control circuit  82 , and loading of the magnetic tape  7  is commenced. In step S 102 , the magnetic tape  7  is tracked and then data is recorded on or reproduced from the magnetic tape  7 . 
     In step S 103 , A pulse detection sensor  89  detects a pulse generated by the reel motor  8  and transmits the detection result to the MPU  85 . The MPU  85  receives the detection result. If The MPU  85  detects any pulse generated by the reel motor  8 , the processing proceeds to step S 107  to continuously drive the reel motor  8  so that the recording and reproduction operation performed in step S 102  is continued. 
     If The MPU  85  detects no pulse generated by the reel motor  8  in step S 103 , The MPU  85  determines that the reel motor  8  is not rotating even though an electrical signal instructing to drive the reel motor  8  is transmitted from the reel motor drive circuit  88 , and the processing proceeds to step S 104 . The MPU  85  determines in this step the reel motor  8  is not rotating because the magnetic tape  7  is stuck to the magnetic head  2 , hindering the rotation of the reel motor  8 . The MPU  85  determines so based on the fact that no electrical signal instructing the stoppage of the reel motor  8  is supplied from the MPU  85  to the reel motor drive circuit  88 . 
     In step S 104 , as described above with reference to  FIGS. 3A and 3B , the MPU  85  transmit signals instructing to protrude the lifter bar  31  to the lifter drive circuit  83 . The lifter bar  31  of the tape lifter  3  is protruded to eliminate the sticking of the magnetic tape  7  to the magnetic head  2 . In step S 105 , the lifter drive circuit  83  determines whether or not the lifter bar  31  is protruded sufficiently. If it is determined that the lifter bar  31  is not protruded sufficiently, the motor  35  of the tape lifter  3  is driven to protrude the lifter bar  31  further. The determination of whether or not the lifter bar  31  is protruded sufficiently is performed by means of the flag  33  and the photo sensor  34  attached to the lifter bar  31 , based on for example whether or not the lifter bar  31  has moved to a predetermined position, or whether or not the lifter bar  31  has moved by a predetermined amount. If it is determined that the lifter bar  31  is protruded sufficiently, it is presumed that the distal end  32  of the lifter bar  31  has lifted up the magnetic tape  7  to eliminate the sticking of the magnetic tape  7  to the magnetic head  2 . 
     If it is determined in step S 105  that the lifter bar  31  is protruded sufficiently, the lifter bar  31  is retracted in step S 106 , presuming that the sticking of the magnetic tape  7  to the magnetic head  2  has been successfully eliminated. Practically, the motor  35  which has been driven to protrude the lifter bar  31  is rotated reversely to bring the lifter bar  31  back to the original position. Upon completion of the retraction of the lifter bar  31 , the processing proceeds to step S 107 , in which the data recording and reproduction operation performed in step S 102  is resumed. 
     According to this embodiment of the invention as described above, if the pulse detection sensor  89  detects any abnormality during loading of the magnetic tape  7  (for example, if no pulse generated by the reel motor  8  is detected), the magnetic tape device  1  forcibly eliminates the sticking of the magnetic tape  7  to the magnetic head  2  by means of the tape lifter  3 . 
     Therefore, the sticking of the magnetic tape  7  to the magnetic head  2  can be eliminated quickly only when it is confirmed that the magnetic tape  7  is stuck to the magnetic head  2 . 
     While the invention has been particularly shown and described with reference to exemplary embodiment thereof, the invention is not limited to this embodiment. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.