Abstract:
A cable management system comprising a cable flex radius system having at least two opposing curved surfaces to control flex radius of a cable linking a stationary system to a dynamic system is disclosed. The cable management system also comprises a cable strain relief system comprising a cable clamp located on each of the at least two opposing curved surfaces. The system simultaneously provides position biasing of a driven rotating mechanism referenced to a fixed system as well as mechanism backlash control. The system insures consistent cable bend radius and slack management required to insure flex cable cycle life. In one embodiment, the cable management system is comprised of a torsion arm and a spool. In this embodiment, the torsion arm pivots during rotation of the spool. A spring connected to the torsion arm provides the requisite tension force to a cable that links the spool and the torsion arm. In this way, cable movement is controlled not only during operation of a moving mechanism, but also while the mechanism is at rest. Such control is particularly useful in devices which require precise movements, such as media storage devices.

Description:
FIELD 
     The present invention relates generally to cable management systems and particularly to cable management in a stationary system linked to a dynamic system. 
     BACKGROUND 
     Interface cables are used to connect stationary systems to dynamic systems in many types of devices, such as in automated manufacturing devices, mass storage devices, and so forth. However, when a cable has excess slack or is otherwise uncontrolled, it may twist, flap or become entangled, causing the moving system to function improperly. Furthermore, cable life is shortened when its movements are uncontrolled, since it is flexing and bending in an inconsistent manner. For example, if the bend radius of the cable is too tight, wires within the cable can wear out or break. Also, since loose cables take up more room than managed cables, the device itself must be made larger to accommodate these cables. Partial control of cables, such as accumulating a cable in a separate chamber also does not solve the problem, as the cable is still subject to random movements that can include contacting an outer wall of the chamber. In addition to reducing precision operation of the dynamic system, such contact can also cause wearing of cable insulation. 
     In mass storage devices, for example, ribbon cables connect stationary electronics to electronics on moving assemblies, such as a pivot assembly and a lift assembly. Together, these assemblies are used to position a robotic device, i.e., a media transport assembly (MTA), to retrieve the desired media from storage. Uncontrolled slack in the ribbon cables, however, causes bending and flexing of the cables during operation. This flexing can cause the cables to catch on protrusions within the chassis, interfere with sensor operation, bend too tightly, wear out, and so forth. Furthermore, during pivoting of the pivot assembly, backlash can occur, i.e., movement or play in gear teeth alignment, which also reduces the resolution and repeatability in positioning of the MTA. 
     For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for providing improved cable management in a dynamic system linked to a stationary system. 
     SUMMARY 
     A cable management system comprising a cable flex radius system having at least two opposing curved surfaces to control flex radius of a cable linking a stationary system to a dynamic system is disclosed. The cable management system also comprises a cable strain relief system comprising a cable clamp located on each of the at least two opposing curved surfaces. The system simultaneously provides positional control of the cable and biased backlash of the gears in the dynamic system. The system insures consistent cable bend radius and slack management required to insure flex cable cycle life. 
     In one embodiment, the cable management system is comprised of a torsion arm and a spool. In this embodiment, the torsion arm pivots during rotation of the spool. A spring connected to the torsion arm provides the requisite tension force to a cable that links the spool and the torsion arm. In this way, cable movement is controlled not only during operation of a moving mechanism, but also while the mechanism is at rest. Such control is particularly useful in devices which require precise movements, such as media storage devices. 
     The components comprising the cable management system are simple and inexpensive, thus factory installation specifications are easy to maintain. As a result, an additional advantage of the present invention includes the ability to easily retrofit manufactured devices with the cable management system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a cable management system in a wound position in one embodiment of the present invention. 
     FIG. 2 is a perspective view of a cable management system in an unwound position in one embodiment of the present invention. 
     FIG. 3 is a perspective view of a portion of the cable management system shown in FIG. 1 connected to a fixed gear in one embodiment of the present invention. 
     FIG. 4 is an exploded perspective view of a torsion arm for the cable management system in one embodiment of the present invention. 
     FIG. 5 is a perspective view of a spool for the cable management system in one embodiment of the present invention. 
     FIG. 6 is a cut-away perspective view of a cable management system in place in a media storage device in one embodiment of the present invention. 
     FIG. 7 is an alternative perspective view of a cable management system in place in a media storage device in one embodiment of the present invention. 
     FIG. 8 is a flow chart diagram of a method embodiment of the present invention. 
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following detailed description of embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and logical, structural, electrical, and other changes may be made without departing from the scope of the present invention. 
     FIG. 1 shows one embodiment of a cable management system  100  for a pivot assembly  101 . In this embodiment, the pivot assembly (hereinafter “rotating assembly”)  101  rotates in a horizontal plane. The rotating assembly  101  (together with a lifting assembly) assists a media transport assembly (MTA) (commonly referred to as a “pick and place” mechanism or “picker”) in moving media within a media storage device, such as a jukebox. (See FIGS.  6  and  7 ). In the embodiment shown in FIG. 1, it is the rotating assembly  101  on which the cable management system  100  is operational, although the invention is not so limited. 
     The cable management system  100  comprises a torsion arm  102  and a spool  104 . The torsion arm  102  has a curved endpiece as shown in FIG. 1, and prevents twisting and bending of the cable  106 . The torsion arm  102  also creates tension in the cable, thus providing positive tension control. A cable  106  in a “wound” position extends along the length of the torsion arm  102  and around the spool  104  as shown. The torsion arm  102  is connected to a chassis  103 , such as the top of a jukebox, with pivotable connecting means  110 . The torsion arm  102  is also connected to a different portion of the chassis  103 , such as the side of a jukebox, with a spring  112 . The other end of the spring  112  is connected to a knob  105  on the torsion arm  102 , although the invention is not so limited. The spool  104  is in communication with and rotates about a fixed gear  130  that is affixed to the chassis  103  (shown in FIG.  7 ). 
     The torsion arm  102  shown in FIG. 1 has a straight portion and a curved portion, or endpiece, with flanges  107  located on the straight portion. The curvature provides a controlled radius for the cable  106 . Attached to the torsion arm  102  are three torsion arm clamps  114 , although the invention is not so limited. Any number of torsion arm clamps  114  can be used. In another embodiment, the torsion arm clamps  114  are integral with the torsion arm  102 , and are not manufactured as separate components. All of the torsion arm clamps  114  help to secure the cable  106  to the torsion arm  102 . The torsion arm clamp  114  located on the curved portion, however, also serves to provide strain relief for the cable  106 . The torsion arm  102  pivots about the vertical axis of the pivoting means  110  as the cable  106  moves. Resistance to pivoting, i.e, tension, is provided by the spring  112 . 
     The spool  104  has a spool clamp  118  to secure the cable  106  in place and to provide additional strain relief for the cable  106 . In another embodiment, the spool clamp  118  is integral with the spool  104 . In addition to the curved endpiece of the torsion bar  102 , the spool  104  also serves to provide a controlled radius for the cable  106 . Thus, the torsion arm  102  and spool  104  of the present cable management system  100  are together providing a positively controlled flex radius system, which provides many advantages, including helping to extend cable life. 
     Media storage devices, commonly referred to as “jukeboxes,” are well-known in the art and will not be discussed in detail herein. Media storage devices include not only “bookshelf” type devices that operate in the x-y directions, but also devices such as those shown herein, that operate in the y-θ directions, i.e., vertically and rotationally. Those that operate in the y-θ directions typically have a lifting assembly for operating in the y direction and a pivot assembly for operating in the θ direction. Again, in the embodiment shown in FIG. 1, the pivot assembly is a rotating assembly  101  that rotates in a horizontal plane about a fixed center point or pivot. The lifting assembly is not shown in FIG. 1, although it is designed to move along a vertical gear rack  134  shown in FIG.  1 . The rotating assembly  101  contains an upper plate  122  and lower plate  125  (sometimes referred to as a “spinner plates”) with two support columns  124  in between that provide support for the upper plate  122 . The entire rotating assembly  101  rotates together about an upper pivot  133  and a lower pivot  127 . The upper pivot  133  is any suitable type of shaft, such as the “knob” shown in FIG. 1, that engages a bearing  135  in the fixed gear  130 . The lower pivot  127  is any suitable type of shaft that engages a bearing fixed to the chassis  103 . The upper plate  122  provides a base for a circuit board  120 , motor mount  121 , rotating motor  126 , pinion gear  128  and sensors  132 . The rotating motor  126  drives the pinion gear  128  around the circumference of the fixed gear  130  in a substantially circular path  131  as shown. Sensors  132  attached to the motor  126  are used to properly position the rotating assembly  101  and therefore the MTA. 
     The spool  104  is designed to fit over the top of the circuit board  120  so that a connector  138  located at the end of the cable  106  can be secured to the circuit board  120 . The spool  104  includes a slot  140  through which the circuit board  120  protrudes. The spool clamp  118  described above also serves to prevent excess force from being placed on the circuit board  120  during operation. 
     Any type of flexible cable connected between two members, wherein the distance between the members is variable, can benefit from the cable management system  100  of the present invention. Although the invention is described in terms of a ribbon cable, a cable of any shape, such as a round or rectangular or irregularly-shaped cable can also be used. The cable  106  can be any suitable length and width. In one embodiment, the cable  106  is up to about 1.5 meters (about five (5) feet) in length and up to about 4.25 cm (about 1.7 in) in width. In another embodiment, the cable  106  is greater than 1.5 meters in length and eight (8) cm in width. In a particular embodiment, the cable  106  is a ribbon cable that is between about six (6) and eight (8) cm (about 2.5 to three (3) in) in width and between about 1.2 to 1.5 meters (about four (4) and five (5) ft) in length, with the last 0.46 m (1.5 ft) connected to and controlled by the cable management system  100 . 
     The cable management system  100  of the present invention precisely controls and guides cable movement even at high speeds, keeping the length of cable between members in a taut condition, thus eliminating random movements of the cable  106 . In applications where cable movement is extremely rapid, such as in jukeboxes, where between about 100 to 500 swaps per hour take place, random movement of the cable  106  can be particularly disrupting. (“Swaps” refer to moving a piece of media from one location to another). In a particular embodiment, about 400 to 450 swaps per hour is occurring. In such high speed applications, it is possible for the rotating assembly  101  to be moving up to about 100 degrees per second (deg/sec), when there is no acceleration. For a spool  104  having a radius of about 3.8 cm (1.5 in), this is up to about 6.6 cm/sec (about 2.6 in/sec) at the outer edge of the spool  104 . In other embodiments, the cable  106  may be moving even faster. In other embodiments, the rotating assembly  101  can be accelerating up to about 270 deg/sec 2 . If the cable  106  is allowed to flex and bend in a random manner, particularly at such high speeds, it is possible that the cable  106  can contact a wall or system component, leading to reduced system performance or even system failure, as well as wearing of cable insulation. 
     As the rotating assembly  101 , and hence the upper plate  122 , rotates in either direction around the path  131 , the cable  106  winds or unwinds around the spool  104 . In one embodiment, the upper plate  122  can rotate up to 180 degrees. In another embodiment, the upper plate  122  is rotatable up to 360 degrees. This movement of the upper plate  122  causes the torsion arm  102  to pivot towards or away from the spool  104 . In FIG. 2, the movement of the upper plate  122  has caused the spool  104  to rotate about 270 degrees in the opposite direction as compared with FIG. 1, such that the cable  106  is now in a “mostly” unwound position. Furthermore, the torsion arm  102  has now moved in a direction away from the spool  104 . Rotation of the spool ( 104 ) 360 degrees from the position shown in FIG. 1 would result in the cable  106  being in a completely “unwound” position with respect to the spool  104 . 
     The actual amount of movement of the torsion arm  102  during rotation of the spool  104  is dependent not only on the amount of spool rotation, but also on other factors such as spool geometry, torsion arm length, and so forth. The cable  106  is necessarily adjusted between these two points during assembly so that there is no slack. Depending on the application, the amount of cable  106  in between these two points can vary from as little as about eight (8) cm (about three (3) in) up to about 30 cm (about 12 in) or more. Furthermore, differences in assembly from one unit to another for a particular type of device can also cause variations in the amount of cable  106  between the two clamps. Such variations can also affect the “starting angle” of the torsion arm  102 , i.e., if less than the required amount of cable  106  is used, the torsion arm  102  may be pulled slightly towards the spool  104  even when the cable  106  is in a completely unwound position. In one embodiment, there is about 15 cm (about six (6) in) of cable  106  between the two clamps. In such an embodiment, the torsion arm  102  moves about 37 degrees when a 7.6 cm (three (3) in) diameter spool  102  is rotated about 330 degrees, about 20 degrees when the same spool  102  is rotated about 180 degrees, and so forth. 
     As noted above, the torsion arm  102  creates a tension force in the cable  106 . Any suitable amount of tension force can be applied as long as cable control is maintained. Testing can be performed to determine a minimum tension force required to achieve cable control in a particular application. Maximum tension biasing forces are dependent on several factors, including, but not limited to, the design of the torsion arm  102  and spool  104 , the means for connecting the torsion arm  102  to the chassis  103 , the means for connecting the spool  104  to the upper plate  122 , and so forth. The type of cable  106  also limits the maximum amount of biasing force that can be applied. However, by using the cable  106  itself to provide positive tension control in the present invention rather than a separate “flex” strap, the cable  106  is not subjected to abrasion or chaffing from contact with a separate strap, which further helps to prolong cable life. 
     The tension force can be created by any suitable means, such as with a torsion spring, wind-up spring or a dead weight on a cable hung over a pulley, and so forth. In the embodiments shown herein, the tension force of the torsion arm  102  is created with a spring  112 , such as an extension spring. The spring  112  can be of any suitable size and placed in any suitable location, as long as it exerts a substantially constant force over its range of travel. Otherwise, the torque applied by the cable  106  to the gears of the rotating assembly  101  can vary, depending on whether the rotating assembly  101  is rotating clockwise or counterclockwise, causing accelerated wearing of the gear teeth. Such variable torque can further cause problems for the electronics driving the rotating motor  126 . Additionally, the biasing force of the cable  106  would not be constant if the torque is not constant. 
     In an alternative embodiment, the spring  112  is a coiled torsion spring. In one embodiment, the spring  112  is applying a force of about nine (9) Newtons (N) (about two (2) lb f ) or less. In another embodiment, the spring  112  is an extension spring applying a force of between about 5.6 N to 7.8 N (about 1.25 to 1.75 lb f ) to a ribbon cable having 68 conductors. In yet another embodiment, the spring  112  is applying a force greater than about nine (9) N. In such an embodiment, multiple cables may be controlled with multiple torsion arms  102  and spools  104 , with the spools  104  stacked on top of each other and the torsion arms  102  also in alignment or on alternating sides of the chassis. 
     An additional feature of the present invention is that it serves to control or bias the backlash of the meshing gears, e.g., fixed gear  130  and pinion gear  128 , even when the mechanism is at rest. The amount of “play” between mating teeth depends on the manufacturing of the gear teeth, but in most instances is between about 0.005 and 0.04 cm (0.002 and 0.016 in). However, with the cable management system  100  of the present invention, this play is controlled by biasing it to one side. Controlling the bias in this manner improves position repeatability and resolution of the MTA, because it no longer “feels” this play in the gear mesh when it stops to pick a media. 
     FIG. 3 shows the fixed gear  130  in place on top of the spool  104 . The cable is not present in this embodiment. The knob  133  shown in FIG. 2 extends into the bearing  135  in the fixed gear  130 , thus providing the pivot point about which the rotating assembly  101  rotates, as described above. Tabs (not shown) from the circuit board  120  extend into upper plate mating holes  304  to help secure the circuit board  120  in place. 
     FIG. 4 shows one embodiment of the torsion arm  102 . The torsion arm  102  can be made from any suitable material, such as wire, steel, plastics, and so forth. The size and geometry of the torsion arm  102  is dependent on the particular application, but should generally be at least about the width of the cable  106  being controlled. Length is also dependent on the particular application. Typically, the torsion arm  102  should be long enough to provide adequate control for the cable  106 . Generally, the longer the torsion arm  102 , the less it pivots. In one embodiment, the torsion arm  102  is about 25 to 35 cm (about 9.8 in to 14 in) in length. In a particular embodiment, the torsion arm  102  is about 30.5 cm (about 12 in) in length. The shape of the torsion arm  102  can vary as long as minimum control is provided. Specifically, the torsion arm  102  should have a minimum radius around which the cable  102  can bend. 
     The radius of the end piece needs to be large enough to prevent excessive bending of the cable  106 . The precise radius needed can be determined using cable radius flex data provided by a cable manufacturer, but is generally greater than the minimum radius flex of the cable. In one embodiment, the torsion arm  102  is a spool such that cable management is achieved with a spool to spool system. This embodiment is particularly useful in applications having tight space limitations. In another embodiment, the curved end piece shown in FIGS. 1 through 3 is replaced with a spool. In one embodiment, the end piece is a curved portion about 0.6 cm (about 0.25) in to about ten (10) (about four (4) in) or more in length with a curve of between about 45 and 60 degrees. In another embodiment, the end piece is a spool having a diameter of between about 2.5 and 7.6 cm (about one (1) in and three (3) in). In a particular embodiment, the torsion arm  102  is about 6.4 cm (about 2.5 in) wide, about 30.5 cm (about 12 in) in length with a curved end piece about 1.3 cm (about 0.5 in) long, with a curvature of about 45 degrees. (A similarly sized circular end piece would have a diameter of about 6.4 cm). 
     The torsion arm  102  further comprises two lips or flanges  107  along the top and bottom edges for added strength. In this way, the torsion arm  102  does not bend or flex during operation and will not permanently deform. The torsion arm clamps  114  can be made from any suitable material, such as sheet metal with two suitably placed holes through which self-contained pins can go through. 
     The torsion arm  102  further has openings  402 A and  402 B through which the pivotable connecting means  110  is placed. The pivotable connecting means  110  is comprised of any suitable shaft or pin that allows the torsion arm  102  to pivot. In the embodiment shown in FIG. 4, the pivotable connecting means  110  is comprised of a pivot bolt  404 , pivot nut  406 , pivot shaft  408  through which the pivot bolt  404  is inserted, and two bearings  410 A and  410 B. The pivot bolt  404  is threaded into a fixed nut in the chassis (not shown) after exiting the upper opening  402 A in the torsion arm  102 . 
     FIG. 5 shows one embodiment of the spool  104 . In this embodiment, the spool has a rim  502  having holes through which screws are placed to secure it to the upper plate  122  (shown in FIGS.  1 - 3 ). Spool mating holes  504  on top of the spool  104  receive tabs from the circuit board  120  to secure the circuit board to the spool  104 . These are similar to the upper plate mating holes  304  shown in FIG. 3, which receive tabs from the bottom of the circuit board  120 . (See FIG. 3) 
     The spool  104  can be made from any suitable material. In one embodiment, the spool  104  is made from any type of smooth material having minimal friction. In another embodiment, the spool  104  is made from sheet metal or any type of plastic, including but not limited to acetal plastic, polypropylene, and so forth. The spool  104  can be any suitable size as long as it is greater than the minimum bend radius of the cable  106  and is sized appropriately in relation to the curved endpiece on the torsion arm  102 . Generally, the smaller the spool  104  (and curvature on the end piece  102 ), the less the torsion arm  102  moves, reducing the chances of the torsion arm  102  touching other components. This is of particular advantage in applications where size is an important consideration, such as small devices containing numerous components. 
     FIG. 6 shows the torsion arm  102  and spool  104  of the present invention in use in a jukebox  600 . Media storage racks  602  are also shown in this embodiment. Activation of the jukebox  600  can be accomplished with a suitable controller  604  and databus  606 . Additionally, the jukebox  600  in this embodiment has external buttons  608  that can be pressed to perform certain operations. FIG. 7 is another perspective of the jukebox  600 . In this embodiment, a lifting motor  726  and associated components can be seen. In one embodiment, each of the motors ( 126  and  726 ) further comprise a processor and a memory, the memory capable of storing a plurality of operating commands for the motor, and the processor capable of executing the stored commands to operate the motors. 
     In operation, as shown in FIG. 8, a command is issued  802  from a controller to a device to perform a specific function, such as retrieve a piece of media from storage and place it in a drive, i.e., place information on-line. The media may be in any number of formats, such as optical disk, tape cartridge, floppy disk, CD, DVD, and so forth. The system has the appropriate motors and electronics known in the art to perform the requested function. In response, a motor is activated  804 , causing an MTA to move into alignment with storage walls. This alignment is accomplished through movement of the rotating assembly (and can also include vertical assembly movement in addition to or instead of rotating assembly movement). Movement of the rotating assembly causes a spool to rotate  806  in the bearing. As the spool rotates, cable winds or unwinds  808  around the spool. The movement of the cable causes a torsion arm onto which the cable is attached to pivot  810  towards or away from the spool. 
     With the cable management system of the present invention it is now possible to continuously track cable location in systems in which the cable interfaces between a stationary system and a dynamic system. As such, the cable management system provides a single solution to multiple design issues. The system provides interface cable control with reliable and consistent flex radius to insure system reliability and improve cable life. The biasing characteristics of the system also improve mechanism positioning repeatability without the use of expensive components. The system has the added advantage of minimizing internal space requirements in a device due to positive tension control of cable at all times. This sustained force in conjunction with the strain reliefs provided may also reduce overall system failures caused by sudden jolts caused by any type of unexpected or unintended external force. The system also has application in zero gravity, low gravity, varying g-force or varying axis environments. 
     Linear mechanism applications, i.e., vertical or horizontal applications, can also benefit from the positive tension control provided by the interface cable in this system. Motion dampening devices can also be added to enhance the effectiveness of the control features described above. However, the use of the torsion arm in the present invention likely already reduces “settling” time of the MTA, i.e., the vibrations that occurs when the MTA stops abruptly to pick media. Specific tests can be designed to determine the dampening effects of the cable management system that occur presently, without added motion dampening devices. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the invention. It is intended that this invention be limited only by the following claims, and the full scope of equivalents thereof.