Abstract:
In a tape data storage arrangement, a magnetic detent is provided to maintain a tape read/write head in selected positions with respect to the tape, during data transfer. The tape is mounted on a carriage movable between first and second positions, with respect to a support structure, and a detent member is fixably joined to the support structure. First and second detent components mounted on the carriage engage the detent member by means of a magnetic force, when the carriage is moved to the first and second positions, respectively. Usefully, the detent member is a magnet and the first and second components comprise steel. Alternatively, the detent member comprises steel, and the first and second components are both magnets.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention disclosed and claimed herein generally relates to detent apparatus for a positioning mechanism or actuator assembly for a tape transducer. More particularly, the invention pertains to detent apparatus of the above type wherein a magnetic force is used to firmly retain a tape transducer in one or more selected positions. Even more particularly, the invention pertains to detent apparatus of the above type wherein the tape transducer comprises a read/write head for a data storage arrangement using magnetic tape. 
   2. Background of the Invention 
   In a common data storage arrangement using magnetic tape, it is necessary to move the read/write head to different positions with respect to the tape. More particularly, the tape head, which is provided to selectively read data from and write data onto the tape, may need to be moved laterally across the width of the data storage tape. This may be necessary to place the head in operative relationship with any of two or more data bands or tracks positioned along the tape length. 
   In view of the above requirements, tape head actuators have been developed, to move the tape head from one band to the other. Some of these actuators have two modes of operation, a first mode for moving the tape head between bands, and a second mode for maintaining alignment between the head and a particular data band. Prior art devices of this type are disclosed, for example, in U.S. Pat. No. 6,437,946, issued Aug. 20, 2002. 
   In prior art tape head actuators as described above, a latching or holding mechanism of some type is generally provided to retain the tape head in place, after the head has been moved into position with respect to one or another of the bands. The retaining mechanisms currently available tend to use spring retainers or detents, and have mechanical components in contact with one another. Vibration or relative motion generally occurs in a tape actuator during tape movement. As a result, reliability and performance problems have been encountered, resulting from such things as component fatigue, component wear and unpredictable frictional forces at detent component interfaces. More particularly, the vibratory movements cause retainer components to rub together, generating friction. Moreover, the rubbing action can cause undesirable debris to be generated and to fall into the actuator or onto the tape or tape head. Also, use of a spring in a head actuator retainer or detent can allow vibrating motion that is of an unpredictable nature. 
   SUMMARY OF THE INVENTION 
   An improved detent design for a tape actuator or positioning mechanism is provided, that eliminates relative contact motion between interfacing detent components. The detent design thereby substantially reduces or eliminates friction in the detent mechanism. In addition, the number of parts in the detent assembly is reduced significantly, compared to prior art configurations. Accordingly, reliability and performance are increased, while costs may be reduced. In one useful embodiment, the detent apparatus comprises a support structure, and a carriage disposed to move between a first position relative to the support structure and at least a second position relative thereto, in order to selectively position and re-position the tape transducer. A detent member is fixably joined to the support structure, and first and second detent components are mounted to the carriage for movement therewith. The first and second detent components are each disposed to engage the fixably joined detent member by means of a magnetic force, when the carriage is moved to the first and second positions, respectively. The magnetic engagements respectively act to retain the carriage at the first and second positions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use and further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a schematic view showing a read/write tape head having multiple positions that may be used with an embodiment of the invention. 
       FIG. 2  is a side view showing an embodiment of the invention. 
       FIG. 3  is a perspective view showing the embodiment of  FIG. 2 . 
       FIG. 4  is a side view showing the embodiment of  FIG. 2  in place within a tape head actuator assembly. 
       FIG. 5  is a perspective view showing the actuator assembly of  FIG. 4 . 
       FIG. 6  is a perspective view showing the read/write head of  FIG. 1  positioned upon the actuator assembly of  FIG. 4 . 
       FIG. 7  is a side view showing a further embodiment of the invention. 
       FIG. 8  is a perspective view showing the embodiment of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , there is shown a section of magnetic data storage tape  102 , moving across a tape transducer such as a read/write head  104 . The tape head  104  selectively reads data from, and writes data onto, the moving tape  102 . More particularly, data is exchanged between tape head  104  and a band or track  106  included in tape  102 , when tape head  104  is in a lower position as shown in  FIG. 1 . However, when tape head  104  is moved along a path of travel to a position  110 , the tape head reads data from or writes data onto a tape track  108 . The embodiment of the invention disclosed hereinafter is constructed to hold or retain tape head  104  in a selected or desired one of its two positions. 
   Referring to  FIG. 2 , there is shown a magnetic detent mechanism  200 , comprising an embodiment of the invention, provided with a permanent magnet  202 . Magnet  202  has flat or planar end surfaces  202   a  and  202   b , in opposing relationship with one another.  FIG. 2  further shows the magnetic detent  200  also provided with an integral steel member  204 , having end elements  204   a  and  204   b . As disclosed hereinafter in further detail, steel member  204  is mounted for movement with respect to magnet member  202  along a detent path of travel. Moreover, when steel member  204  is moved to the lowest extent of its travel path, a planar surface of steel end element  204   a  is brought into abutting contact with planar magnet end surface  202   a . Thereupon, the magnetic force provided by magnet  202  acts to lock or retain magnet  202  and steel member  204  into firm, fixed relationship with each other. Magnet  202  and the abutting planar surfaces are respectively selected to provide a magnetic force that will be sufficient to ensure that magnet  202  and steel member  204  remain fixed together, with little or no rubbing therebetween, until a counter force is applied to intentionally overcome the magnetic force. 
   When such counter force is applied, steel member  204  is moved upwardly along its path of travel, as viewed in  FIG. 1 , until a planar surface of end element  204   b  and magnet end surface  202   b  are brought into abutting contact with one another. Thereupon, the magnetic force provided by magnet  202  will retain the magnet  202  and steel member  204  in this new position. 
     FIG. 3  shows a further view of detent magnet  202  and steel detent member  204  of magnetic detent  200 . 
   Referring to  FIGS. 4 and 5  together, there is shown detent magnet  202  fixably joined to an outer carriage  402 . There is further shown steel detent member  204  fixably attached to an inner carriage  404 , wherein inner carriage  404  is constrained to limited linear movement with respect to outer carriage  402 . This movement is upward or downward, as viewed in  FIGS. 4 and 5 . More particularly, outer carriage  402  is provided with brackets  406  and  408 , that collectively support a guide rail  410 . Outer carriage  402  is further provided with a bracket  412  that supports a guide rail  414 . Inner carriage  404 , and steel detent member  204  joined thereto, are disposed to move along guide rails  410  and  414 , between their upper and lower limits of travel. These limits are determined or established by the specific construction of outer carriage  402 . 
   As described hereinafter in connection with  FIG. 6 , inner carriage  404  is designed to support and carry read/write tape head  104 . Accordingly, the lower and upper limits of travel of inner carriage  404  are judiciously selected, in order to position tape head  104  to exchange data with either tape band  106  or  108 , as inner carriage  404  is moved to its lower or upper limit, respectively. 
   Detent magnet  202  and steel detent member  204  are respectively mounted so that end element  204   a  and magnet surface  202   a  are brought into closely abutting contact when inner carriage  404  is moved to its lower limit. The magnetic retention force that is thereby established between steel detent member  204  and detent magnet  202  will act to hold both the inner carriage  404  and tape head  104  mounted thereon firmly in this position. Similarly, when inner carriage  404  is moved to its upper limit, end element  204   b  and magnet surface  202   b  are brought into contact, to likewise establish the magnetic force between magnet  202  and steel member  204 , whereby inner carriage  404  and tape head  104  will be held in this latter position. 
   Referring to  FIG. 6 , there is shown outer carriage  402 , inner carriage  404  and components  202  and  204  of magnetic detent  200  supported upon a linear drive motor  602 , and held in place thereon by means of a frame  604 .  FIG. 6  also shows read/write tape head  104  mounted on inner carriage  404 . A linkage (not shown) is provided between motor  602  and inner carriage  404 , to enable linear motor  602  to move inner carriage  404 , and to thus move tape head  104  between its respective positions of operation, as desired. As described above, magnetic detent  200  operates to lock tape head  104  into a selected one of its positions with respect to the magnetic tape. The locking force provided by magnetic detent  200  will continue to act, until overcome by operation of motor  602  to re-position the inner carriage  404  and tape head  104 . 
   Referring further to  FIG. 6 , there is shown outer carriage  402  supported in frame  604  by means of brackets such as bracket  406 . Each of these brackets provides flexure between outer carriage  402  and frame  604 , so that outer carriage  402  is allowed to move slightly with respect to frame  604 . When inner carriage  404  is held in one of its positions by magnetic detent  200 , as described above, the holding force provided by the magnetic detent will be sufficient to move inner carriage  404  and tape head  104  in unison with outer carriage  402 . This, in turn, allows tape head  104  to move slightly, to adapt to vibrations associated with movements of the data storage tape  102 . 
   Referring to  FIGS. 7 and 8  together, there is shown an alternative magnetic detent  700 , comprising a second embodiment of the invention. Magnetic detent  700  is provided with an integral steel detent member  702 , having end elements  702   a  and  702   b , each provided with an outwardly facing planar surface. Detent  700  is further provided with magnet components  704  and  706 , each comprising a permanent magnet. Magnet  704  has a planar surface  704   a  in facing relationship with the planar surface of steel end element  702   a , and magnet  706  has a planar surface  706   a  in facing relationship with the planar surface of steel end member  702   b.    
   In substituting magnetic detent  700  for the previously described magnetic detent  200 , the steel member  702 , rather than detent magnet  202 , would be fixably joined to outer carriage  402 . Magnet components  704  and  706  would each be attached to inner carriage  404 , for movement therewith, instead of attaching steel member  204  thereto. Usefully, magnet  704  would be joined to inner carriage  404  at the point of attachment thereto of end element  204   a , as shown by  FIG. 4 . Similarly, magnet  706  would be joined to inner carriage  404  at the point of attachment thereto of end element  204   b , as further shown by  FIG. 4 . 
   In the arrangement shown in  FIGS. 7 and 8 , movement of inner carriage  404  to its lowest position would bring the planar end surface of steel end member  702   a  into abutting contact with planar surface  704   a . Thereupon, the magnetic force provided by magnet  704  acts to lock or retain magnet  704  and steel detent member  702  in fixed relationship with each other. When an upward force is applied to inner carriage  404  by motor  602 , the magnetic force between magnet  704  and steel member  702  is overcome. Magnets  704  and  706  move upwardly with inner carriage  404 , along the detent path of travel, until planar magnet surface  706   a  and the planer surface of end element  702   b  are brought into abutting contact with one another, to establish a retentive magnetic force therebetween. 
   The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.