Abstract:
A magazine assembly containing numerous media units is disposed adjacent to a picker assembly. One of the two assemblies is normally stationary, while the other assembly is a traveling assembly. In either case, the two assemblies cooperate with one another to selectively provide the picker assembly with access to the media units that are stored in the magazine assembly. A motion reversal assembly is coupled to the normally stationary assembly and is engageable by the traveling assembly when it enters an end portion of its excursion path. When the motion reversal assembly is so engaged, it moves the normally stationary assembly in the direction opposite to that of the traveling assembly&#39;s movement. The effect is an apparent increase in the traveling assembly&#39;s available excursion length, which makes it possible for the picker assembly to access media slots that would otherwise be disposed in the dead spaces located on either end of the traveling assembly&#39;s excursion path.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to electromechanical information storage systems. More particularly, the invention relates to media autochangers used in such systems. 
     BACKGROUND 
     Media Autochangers. Electromechanical information storage systems are commonly used, for example, to create automated libraries for data storage and backup. Many such automated libraries make use of one or more media autochangers, also known as media jukeboxes, to provide large storage capacity relatively inexpensively. In a media autochanger, numerous media units such as discs or tape cartridges can be stored and then independently selected by a picker mechanism for engagement with a drive. Because of the markets into which media autochangers are sold and the environments in which they are employed, it is important to maximize storage density in such systems while minimizing cost as much as possible. 
     One class of media autochangers seeks to address these concerns by employing a stationary picker assembly in conjunction with a traveling magazine of media units. A typical example of this class of autochangers has the media units mounted on a circular rotating carousel. A control mechanism is used to rotate the carousel until a desired media unit is located adjacent to the stationary picker assembly. The desired media unit is then accessed by the picker mechanism for read or write operations. Carousel designs such as these fail to maximize storage density because the media units in the carousel are necessarily angled relative to one another. This creates angular dead spaces between the media units. 
     In higher-end products of this class, the picker mechanism is capable of movement in a direction parallel to the carousel&#39;s axis of rotation but not along the arc of rotation. For example, the carousel can rotate about the z axis while the picker moves up or down in the z direction to access stacked discs or cartridges rotating on the carousel. (By way of background, it is believed that the Breece Hill Technologies, Inc. “SAGUARO” library and the Exabyte Corporation “690D” library both operate in this manner.) These devices remain within the general class of devices wherein the picker assembly is “stationary,” because the picker assembly itself is not capable of movement in the direction of the magazine assembly. These higher-end products not only share the angular dead space problem with their lower-end counterparts, but they also suffer from higher cost associated with providing separate drive mechanisms for the picker and the carousel. 
     Another class of media autochangers employs a stationary media magazine in conjunction with a traveling picker assembly. In these systems, the media magazine takes the form of a linear array of media slots. In linear designs such as this, the picker assembly moves parallel to the axis of the media slot array from one end to the other in order to access the individual media units mounted therein. (By way of background, it is believed that the ADIC, Inc. “Fastor DLT7” autochanger operates in this manner.) The benefit of linear designs is that angular dead spaces between media units are inherently eliminated. 
     End-of-Travel Dead Space. One problem that is common to most of the linear designs is that of dead space on the ends of the picker&#39;s excursion path. A combination of motors, gears, tracks, circuit boards and housings are typically required to implement a picker and to define its excursion path. Consequently, the picker is usually wider than a media slot. In addition, the footprint of the components used to define the excursion path of the picker is usually longer than the length of the media magazine. These factors, either independently or in combination, inevitably impose a minimum on at least one dimension of the autochanger&#39;s enclosure. The result is that dead space occurs between the ends of the media magazine and the walls of the enclosure. For similar reasons, even autochangers of the carousel variety can suffer from the end-of-travel dead space problem if the carousel travels along a finite arc rather than in an endless circle. 
     It is therefore an object of the invention to enhance the storage density of media autochangers by eliminating end-of-travel dead space. 
     It is a further object of the invention to eliminate end-of-travel dead space according to a technique that can be applied in autochangers of the linear variety as well as to those of the carousel variety. 
     SUMMARY OF THE INVENTION 
     The invention includes numerous aspects, each of which contributes to achieving the above and other objects. In one aspect, a magazine assembly containing numerous media units is disposed adjacent to a picker assembly. One of the two assemblies is normally stationary, while the other assembly is a traveling assembly. In either case, the two assemblies cooperate with one another to selectively provide the picker assembly with access to the media units that are stored in the magazine assembly. A motion reversal assembly is coupled to the normally stationary assembly and is engageable by the traveling assembly when the traveling assembly enters an end portion of its excursion path. When the motion reversal assembly is so engaged, it moves the normally stationary assembly in the direction opposite to that of the traveling assembly&#39;s movement. The effect of this movement is an apparent increase in the traveling assembly&#39;s available excursion length. This makes it possible for the picker assembly to access media slots that would otherwise be disposed in the dead spaces located on either end of the traveling assembly&#39;s excursion path. 
     In media autochangers that employ the invention, additional media slots may be provided in the magazine without increasing the available excursion length of the traveling assembly or the area required to house the device. This achieves enhanced spacial and storage density. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top/front oblique view of a magazine assembly and a motion reversal assembly according to a first preferred embodiment of the invention. 
     FIG. 2 is a bottom/rear oblique view of the apparatus of FIG.  1 . 
     FIGS. 3 and 4 are top views of the apparatus of FIG. 1 disposed adjacent to a picker assembly according to a first preferred embodiment of the invention. In FIG. 3, the magazine assembly is shown in a rest position. In FIG. 4, the magazine assembly is shown in a translated position. 
     FIG. 5 is an exploded view of the magazine assembly system of FIG. 1, showing a car assembly and a removable magazine. 
     FIG. 6 is an exploded view of the car assembly of FIG.  5 . 
     FIG. 7 is an oblique view of one of the wheel guides of the car assembly of FIG.  5 . 
     FIG. 8 is an oblique view of the car chassis of the car assembly of FIG.  5 . 
     FIG. 9 is an oblique view of the magazine retention lock of the car assembly of FIG.  5 . 
     FIGS. 10 and 11 are oblique and orthogonal views, respectively, of the motion reversal lever of the car assembly of FIG.  5 . 
     FIG. 12 is a schematic diagram summarizing the embodiment shown in FIGS. 1-11. 
     FIG. 13 is a schematic diagram illustrating a second preferred embodiment of the invention in which the magazine assembly is a traveling assembly, the picker assembly is a normally stationary assembly, and the autochanger is of the linear variety. 
     FIG. 14 is a schematic diagram illustrating a third preferred embodiment of the invention in which the picker assembly is a traveling assembly, the magazine assembly is a normally stationary assembly, and the autochanger is of the carousel variety. 
     FIG. 15 is a schematic diagram illustrating a fourth preferred embodiment of the invention in which the magazine assembly is a traveling assembly, the picker assembly is a normally stationary assembly, and the autochanger is of the carousel variety. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment One 
     FIGS. 1 and 2 provide a structural overview of a magazine movement system  100  according to a first preferred embodiment of the invention in which the magazine assembly is a traveling assembly, the picker assembly is a normally stationary assembly, and the autochanger is of the linear variety. A magazine assembly  102  includes a linear array of media slots  104 . Each media slot  104  may be used to contain one media unit. In the illustrated embodiment, each of slots  104  is configured to receive one tape cartridge. In other embodiments, slots  104  may be configured to receive media units of a type other than tape cartridges. Magazine  102  is removably mounted to a car  106 . Car  106  is retained in a track  108 . Track  108  is defines a linear path of movement for car  106 . 
     In the embodiment shown, motion reversal assembly  110  is mounted to the bottom of track  108  and includes a lever  112  having an axis of rotation  200 . Lever  112  has a slot  203  coupled to magazine assembly  102  via a pin  204  on the underside of car  106  as shown. (Other suitable coupling methods may also be used.) Lever  112  has a surface  114  that extends away from track  108  into the excursion path of a moving picker assembly. Further details about motion reversal assembly  110 , including various alternative embodiments thereof, will be provided below. 
     Magazine assembly  102  is biased toward the rest position illustrated in FIGS. 1 and 2. In the embodiment shown, this biasing is accomplished with a torsion spring  206 . Specifically, leg  208  of torsion spring  206  is retained by a notch in bearing surface  210  on the underside of track  108 , and leg  212  of torsion spring  206  is retained under a lip  214  on lever  112 . This arrangement urges lever  112  toward the clockwise direction (viewed from beneath, as in FIG.  12 ), which in turn urges magazine assembly  102  toward the rest position illustrated in FIGS. 1 and 2. Other techniques may be used to bias magazine assembly  102  toward the rest position. Further movement of magazine assembly  102  by torsion spring  206  beyond the rest position is prevented by the engagement of pin  204  with the end of track slot  216  and by the engagement of car tab  218  with the end of track slot  220 . During the movement of car  106  within track  108 , car tabs  218 ,  222  travel within track slots  216 ,  220  to aid alignment of car  106  within track  108 . 
     The preferred operation of magazine movement system  100  will now be described with reference to FIGS. 3 and 4. In FIGS. 3 and 4, magazine movement system  100  is shown adjacent to a traveling picker assembly  300 . Picker assembly  300  has an excursion path  302  that includes an end portion  304 . Surface  114  of lever  112  is disposed within end portion  304  of excursion path  302 . In FIG. 3, magazine assembly  102  is shown in its rest position. When picker assembly  300  is caused to travel in direction A and to enter end portion  304  of excursion path  302 , picker assembly  300  engages surface  114  of lever  112 . This moves lever  112  in the clockwise direction (viewed from the top as in FIG.  3 ), which in turn moves magazine assembly  102  away from the rest position toward direction B. Direction B is opposite to the direction of movement of picker assembly  300 . 
     Moving magazine assembly  102  and picker assembly  300  in opposite directions simultaneously reduces the excursion distance required for picker assembly  300  to reach the end-most slot in magazine assembly  102 . For example, in the embodiment shown, the slot numbered “1” in magazine assembly  102  would be inaccessible by picker assembly  300  if it were not for magazine movement system  100 . Preferably, an automatic control system should be provided and calibrated such that picker assembly  300  will stop its movement in direction A when it is aligned with the media slot numbered “1” as shown in FIG.  4 . The implementation of such a control system will not be described herein; its details are beyond the scope of the invention, and persons of ordinary skill in the art will be able to utilize well-known techniques to construct it suitably without undue experimentation. It will suffice to note herein that the travel distance required for picker assembly  300  to move between adjacent media slots is larger when magazine assembly  102  is in the rest position, and smaller when magazine assembly  102  is moving away from the rest position in direction B. Any control system chosen for operating picker assembly  300  must take this difference into account. 
     When picker assembly  300  is caused to travel back away from end portion  304  toward direction B, torsion spring  206  moves magazine assembly  102  toward direction A, returning it to its rest position as soon as picker assembly  300  disengages from lever  112 . 
     Further structural details of magazine movement system  100  will now be described with reference to FIGS. 5-16. FIG. 5 illustrates an optional implementation of magazine assembly  102  in which magazine  103  is removable from car  106 . In FIG. 5, magazine  103  has been removed from car  106  by depressing spring-loaded magazine lock  500  and sliding magazine  103  away from car  106  along the line indicated by arrow  502 . Magazine  103  is mounted to car  106  by sliding it along line  502  so that lips  506  pass underneath retaining guides  504 . As sliding continues, a beveled surface (not shown) on the underside of magazine  103  depresses lock  500 . Finally, lock  500  snaps into a locked position within lock retainer area  508  on the back side of magazine  103 . (See FIGS. 3 and 4.) 
     FIGS. 6-9 illustrate car  106  and track  108  in more detail. Magazine lock  500  may be installed onto car  106  by inserting axles  610  through clearance slots  612  and then pushing them backwards until they snap into axle retainers  614 . A compression spring  608  is placed between lock  500  and car  106  and is retained by recess  616  on car  106  and by recess  618  on the underside of lock  500 . Installation is completed by rotating lock  500  down on spring  608  until tabs  620  (one on either side of lock  500 ) snap into clearance holes  622  formed in car  106 . 
     The material of track  108  defines a first wheel guide  600  along one side. (In the embodiment shown, track  108  and wheel guide  600  were fashioned from a single piece of sheet metal.) A second wheel guide  700  may be fashioned within elongate member  602 . (In the embodiment shown, elongate member  602  was made of plastic.) After wheels  606  and  607  are snapped onto car  106  as shown, car  106  may be placed onto track  108 . Wheels  607  should be retained within wheel guide  600 ; pin  204  should extend downward through track slot  216 ; and car tabs  218  and  222  should be disposed within track slots  220  and  216 , respectively. Elongate member  602  should be mounted onto track  108  so that it retains wheels  606 . (In the embodiment shown, elongate member  602  was mounted to track  108  by inserting mounting tabs  702 ,  704  into slots  602 ,  604 . Other suitable attachment methods may, of course, be used.) 
     Motion reversal assembly  110  will now be discussed in detail with reference to FIGS. 10-11. In the embodiment shown, a single lever  112  is used to implement motion reversal assembly  110 . Lever  112  and torsion spring  206  may be rotatably mounted to the underside of track  108  by any suitable means; for example, with a bolt. Cylindrical member  624  is disposed around axis of rotation  200  and fits inside torsion spring  206 . Surface  114  should be disposed to engage picker assembly  300 , and slot  203  should provide a sliding point of engagement between lever  112  and pin  204 . In the embodiment shown, surface  114  and slot  203  are angularly displaced from one another by approximately  180  degrees relative to axis of rotation  200 . The radii extending from axis of rotation  200  to surface  114  and slot  203  were chosen to be approximately equal. This arrangement provided the desired reversal of motion between picker and magazine in substantially a 1:1 ratio. Other radii and angular displacements may be chosen to achieve alternative ratios. It is believed, however, that in all embodiments that employ a single lever  112  to implement motion reversal assembly  110 , best results will be obtained when surface  114  is angularly displaced from slot  203  by not more than 270 degrees and not less than 90 degrees, as indicated in FIG.  11 . 
     Other means may be used to implement motion reversal assembly  110  depending on the geometry of the magazine and picker assemblies in a given media autochanger. For example, instead of using a single lever, multiple levers, gears, motors or solenoids may be used to accomplish the task of moving the normally stationary assembly in the opposite direction of the traveling assembly when the traveling assembly enters an end portion of its excursion path. It is believed, however, that the single lever implementation will yield desirable cost savings over the alternative means just described. 
     Schematic Summary of Embodiment One 
     FIG. 12 schematically summarizes the embodiment shown in FIGS. 1-11. A normally stationary magazine assembly  1200  is retained on a linear track  1202 . A traveling picker assembly  1204  moves along an excursion path  1206  adjacent to magazine assembly  1200  to access media units mounted in magazine assembly  1200 . When picker assembly  1204  travels to a point near the end of excursion path  1206 , it engages motion reversal assembly  1208 , which causes magazine  1200  to move in direction  1210  opposite to the direction of the picker assembly&#39;s movement. The result is to enable picker assembly  1204  to access one or more media slots in magazine assembly  1200  that would otherwise have been located in the picker assembly&#39;s dead space. 
     Alternative Embodiments 
     Several alternative embodiments of the invention will now be discussed schematically with reference to FIGS. 13-15. 
     Embodiment Two 
     In the embodiment of FIG. 13, a normally stationary picker assembly  1304  is retained on a linear track  1302 . A traveling magazine assembly  1300  moves along an excursion path  1306  adjacent to picker assembly  1304  so that picker assembly  1304  may access media units mounted in magazine assembly  1300 . When magazine assembly  1300  travels to a point near the end of excursion path  1306 , point  1301  engages motion reversal assembly  1308 , which causes picker assembly  1304  to move in direction  1310  opposite to the direction of the magazine assembly&#39;s movement. The result is to enable picker assembly  1304  to access one or more media slots in magazine assembly  1300  that would otherwise have been located in dead space. 
     Embodiment Three 
     In the embodiment of FIG. 14, a normally stationary magazine assembly  1400  is retained on a curved track  1402 . A traveling picker assembly  1404  moves along an excursion path  1406  adjacent to magazine assembly  1400  to access media units mounted in magazine assembly  1400 . When picker assembly  1404  travels to a point near the end of excursion path  1406 , it engages motion reversal assembly  1408 , which causes magazine assembly  1400  to move in direction  1410  opposite to the direction of the picker assembly&#39;s movement. The result is to enable picker assembly  1404  to access one or more media slots in magazine assembly  1400  that would otherwise have been located in the picker assembly&#39;s dead space. 
     Embodiment Four 
     In the embodiment of FIG. 15, a normally stationary picker assembly  1504  is retained on a curved track  1502 . A traveling magazine assembly  1500  moves along an excursion path  1506  adjacent to picker assembly  1504  so that picker assembly  1504  may access media units mounted in magazine assembly  1500 . When magazine assembly  1500  travels to a point near the end of excursion path  1506 , point  1501  engages motion reversal assembly  1508 , which causes picker assembly  1504  to move in direction  1510  opposite to the direction of the magazine assembly&#39;s movement. The result is to enable picker assembly  1504  to access one or more media slots in magazine assembly  1500  that would otherwise have been located in dead space. 
     While the invention has been described in detail in relation to preferred embodiments thereof, the described embodiments have been presented by way of example and not by way of limitation. It will be understood by those skilled in the art that various changes may be made in the form, details, materials and fastening techniques described above without deviating from the spirit and scope of the invention as defined by the appended claims. For example, the “tracks” described above may be implemented in any manner suitable for defining a linear or arcuate path of movement for the picker or magazine assemblies; it is believed that gear assemblies or alternative types of guide channels may produce acceptable results. In addition, the term “picker assembly” is intended herein to include any type of assembly that is cooperatively operable with a magazine assembly to access media units stored therein. Specifically, “picker assembly” is intended to include devices in which a read/write head is placed on or near the media units without withdrawing the media units from the magazine. The term “picker assembly” is also intended to include devices that remove media units from the magazine and place them in a drive.