TECHNICAL FIELD OF THE INVENTION

In one aspect, the present invention relates to novel rings which can be assembled to optical discs to protect them from damage and to facilitate the retrieval of data from the disc by stabilizing it and by damping mechanical vibrations in the disc as it is spun. And, in a second aspect, the present invention relates to the provision of optical discs which are protected from damage during handling and otherwise and which are so stabilized and damped as they are spun that all of the data encoded thereon can be retrieved from the disc.

BACKGROUND OF THE INVENTION

Optical discs with information recorded on one or both sides have come to be used for a variety of purposes, most notably in the music and video industries and as read only computer memories.

The use made of such discs by the music industry is exemplary. Digital information from which an audio signal can be derived is stored on the disc (known as a "compact disc" or CD) in the form of pits arranged along circular, concentric tracks on one side of the disc; and the disc is read — i.e., scanned and the pits detected — with a laser beam as the disc is spun. The digital output from the laser reader is

processed through a digital-to-analog converter and other circuits and thus converted to an audio signal which can be used to drive speakers, headphones, etc. Because a compact disc player uses a laser beam to read the data from the disc in a manner which eliminates physical, pickup-to-disc contact, it uses several servo systems to provide the necessary physical relationships between the laser beam and the disc being read. A focusing servo keeps the laser beam correctly focused so that the pickup can detect the information-related pits on the disc. A tracking servo keeps the pickup over the correct pit track. A CLV servo maintains a constant linear velocity between the laser beam and the track being read by controlling the spindle speed of the motor which rotates the disc.

Because of instability; i.e., imperfect contact between a disc being read and the platter on which the disc is supported (both relatively rigid) at the high speed at which is it rotated, the lack of perfect balance in the spindle which centers the disc on the platter and the disc itself, and other similar factors, the disc will flutter .to a greater or lesser extent as it is being read. Disc flutter (or vibration) can cause angular offset of the laser beam; and this, in turn, can cause coma abberation which is a source of jitter. Increased jitter leads to the worsening of the intersymbol interference and a reduction of the data margin, and ultimately, an audio signal of lower quality than is otherwise available from the data recorded on the disc.

One device for stabilizing an optical disc as it is read and thereby contributing to the ability of the laser pickup to retrieve information from the disc

iε a ring installed with a centering device and attached to the disc with an adhesive.

Although this ring addresses many of the problems encountered in stabilizing an optical disc, it does have disadvantages. One is that the ring is not always centered correctly, which can make disc vibration worse. Another disadvantage is that, once the ring has been applied, it cannot be removed without damaging the disc. Another, important disadvantage is that discs equipped with adhesively attached rings as just described do not fit in all disc players, which limits their usefulness.

SUMMARY OF THE INVENTION

There have now been invented, and disclosed herein, certain new and novel devices for stabilizing and otherwise reducing the vibration in optical discs as they are being read and for protecting such discs as they are handled, if they are dropped, etc. These novel devices overcome the above-discussed and other advantages of heretofore proposed devices for stabilizing optical discs as they are read. In addition, the novel vibration reducing devices disclosed herein have the additional, important capability of ~ protecting such discs as they are handled, if they are dropped, etc.

These devices., generally speaking, are rings fabricated from an elastically distensible material with vibration damping properties. A U-shaped cross-section provides: (1) upper and lower lips which blanket the upper and lower, outer peripheral surfaces of the disc when the ring is installed, and (2) an integral.

lip-connecting rim which surrounds and engages the periphery of the disc to hold it to the disc.

As is apparent from the foregoing, the ring is installed by manipulating the outer peripheral edge of the disc to be stabilized and protected by the ring into the space between the upper and lower lips or flanges of the ring, a small clearance in this respect being provided by appropriate dimensioning of the rim so that the lips will readily slip over the edge of the disc. Installation of the ring in the manner just described is easily accomplished because its elastic properties allow the ring to easily be stretched and otherwise distorted to fit it over the edge of the disc.

Once installed, the ring relaxes toward its uninstalled configuration and diameter, securely locking it in place against the outer periphery of the disc with its upper and lower lips extending inwardly from the periphery of the disc in overlying relationship to its upper and lower disc surfaces. Removal of the ring is equally simple. This is effected merely by pulling it off the disc on which it is installed.

Because the lower lip of the installed ring protrudes below the disc, it reduces the area of contact between the disc-and the platter on which it is supported from a circle equalling the disc in diameter to a thin annulus, thereby promoting more perfect surface-to-surface contact between the disc and platter, stabilizing the disc and reducing its tendency to flutter as it is spun. Vibration is further reduced because the resilient material from which the ring is fabricated allows that ring to deform into essentially complete surface-to-surface contact with both the disc

supporting platter and the lower surface of disc, thereby further stabilizing the disc and reducing the tendency of the disc to vibrate. And, because of the vibration damping properties of the material from which it is made, the ring will absorb to a significant extent vibrations of the supporting platter which might be transmitted to or set up sympathetic vibrations in the disc as well as other vibrations set up in the disc and attributable to such factors as imbalances in the centering spindle of the disc player. Additionally, because of the extra mass provided at the periphery of the disc by the ring, a further stabilizing factor in the form of increased centrifugal force is provided. Its inwardly protruding lower lip keeps the ring from being scratched or otherwise damaged, and information coded into it thereby erased, if the ring is dropped or if the surface on which the information is coded is set down or moved on a rough surface or scraped along a tray, magazine, or carousel as it is loaded. The lips of the ring also provide additional surfaces by which the disc may be handled, making it possible to do so without touching the information-bearing surface 'of the disc and damaging that surface of the disc by scratching or by depositing skin oils on it (the cleaning of a disc to remove skin oils — or other foreign matter so that the laser pickup can "see" the information related pits — is a practice which disc manufacturers strongly recommend be held to a minimum) . Also, the material from which the ring is fabricated will normally be one which will absorb such oils, further insuring that they do not get onto the information bearing surface of the disc by migration from the ring.

Still another advantage of the present invention is that the centering device required in the above-discussed prior art technique for attaching a stabilizer ring to an audio disc is eliminated. Also, because the ring is in effect self-centering, the centering inaccuracies that arise, even when such a device is employed, are eliminated.

Furthermore, the mass added by the ring is a decided benefit as the increased centrifugal force thus ^' generated as the disc is spun to read information therefrom reduces the tendency of the disc to tilt and/or flutter.

At the same time that it provides the many advantages discussed above, the ring does not interfere with the loading of any tray, magazine, or carousel of which I am aware; and most disc cleaners are compatible with discs on which a ring embodying the principles of the present invention is installed.

OBJECTS OF THE INVENTION

From the foregoing, j.t will be apparent to the reader that one important and primary object of the present invention resides in the provision of novel, improved ways of stabilizing optical discs and otherwise reducing vibration in and tilting of such discs as they are read while, at the same time, protecting the disc against the damage that may be caused: while loading it into a disc player tray, carousel, or magazine; or if the disc is dropped or set down on a surface on which information is encoded; or contacted during handling in a manner which might result in skin oils being transferred to an information bearing surface.

Other important objects and features and additional advantages of the invention will be apparent to the reader from the foregoing and the appended claims and as the ensuing detailed description and discussion proceeds in accord with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing: FIG. 1 is an exploded view of an optical disc stabilized and protected in accord with the principles of the present invention;

FIG. 2 is an unexploded view of the disc; and FIG. 3 is a section taken substantially along line 3-3 of FIG. 1 to show the cross-sectional configuration of an elastically extensible ring also constructed in accord with the principles of the present invention and employed to stabilize and protect the disc.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing, FIGS. 1 and 2 depict in exploded and unexploded form, respectively, an optical disk 20 protected, stabilized, and damped in accord with the principles of the present invention by a readily removable ring 22 also embodying those principles.

The illustrated disc 20 is one designed for the storage of audio information and, more specifically, is what is known in the trade as a five inch compact disc or CD. This disc is, however, merely exemplary of those to which the principles of the present invention

are applicable; and that ensuing description of the invention related to disc 20 is therefore intended to be only illustrative and not limiting.

Disc 20 has: (1) a bottom or lower surface (not shown) on which information such as the name of the disc, the company issuing the disc, and the (typically) titles of the songs recorded on it will be printed, and (2) an upper surface 24 on which data convertible to an audio signal is digitally recorded as pits along concentric, circular tracks. ^' A circular opening ^" 25 in the center of disc 24 accommodates a disc player spindle (not shown) which centers disc 24 while it is being spun to read information from it.

It was pointed out above that scratches, scrapes, oil and other foreign substances, etc. on this information bearing surface or side 24 of disc 20 may prevent the laser pickup employed to read the encoded data from extracting part or all of the data from the affected area or areas. Also described were the adverse effect that tilting, flutter, and other forms of movement and vibrations set up in the disc as it is spun to. read information therefrom can have on the ability of the laser pickup to read information from the disc. In the present invention, the information bearing side 24 of disc 20 is protected against damage and the deposit of foreign materials such as skin oils, stabilized, and damped by assembling ring 22 to the disc as shown in FIG. 2.

More specifically, and with disc 20 and the ring 22 assembled to it oriented as shown in FIGS. 1 and 2 with the disc horizontal, damping, stabilizing, and protecting ring 22 has: (1) parallel, spaced apart, upper and lower, annular lips 26 and 28; and (2) an

integral, circular rim 30 which extends from upper lip 26 to lower lip 28 and cooperates with those lips to define a space or recess 32 extending around the circumference of and opening onto the inner periphery 34 of the ring.

Ring 22 completely surrounds the outer edge 34 of disc 20 with the upper lip 26 of the ring blanketing the outer, peripheral portion of the disc's upper side 24 and the lower lip of .the. ring similarly extending over the peripheral portion of the disc's bottom or lower side. It is preferred that these lips be on the order of one-eighth inch wide (dimension "d" in FIG. 3) and that they be on the order of 0.01 plus 0.005 minus 0.002 inch thick. width of the magnitude just identified enables one to easily handle the disc without transferring skin oils from his or her fingers to the disc and thereby making at least a part of that disc fully or partially unreadable. At the same time, widths of that lip will not cover any of the information tracks on disc surface 24.

Lip thicknesses in the desired range keep the disc far enough above a supporting surface that, if disc 20 with the ring 22 assembled to it is accidentally dropped or placed with side 24 down on, and then moved relative to the surface, the disc will not be scratched, scraped or similarly damaged. At the same time, and with the overall height of the ring (dimension "h" in FIG. 3) limited to the preferred ca. 0.09 inch in those incarnations in which the ring is designed for use with a compact disc, that ring will not interfere with the operation of any known compact disc player including

those equipped with carousel- and magazine-type disc changers.

One material from which ring 22 can be made contains polychloroprene and butyl polymers and is loaded with zinc oxide and stearic acid. This material, identified by the tradename Navcom, is available from Sims Vibration Dynamics, Inc., 2797152nd Avenue N.E., Redmond, Washington 98052. It has a very low modulus of elasticity and is, consequentially, particularly capable of damping or absorbing vibrations, including those in the range of 10-30,000 Hz. Therefore, in addition to keeping vibrations from interfering with the reading of data, this material to at least a very large extent keeps those vibrations in the audible frequency range from being outputted from the disc player as a hum or other noise.

Polyurethanes with properties akin to those of Navcom are also available; and the disc protecting and stabilizing ring can be made from compositions of that character, if desired.

As is typical of compositions based on polychloroprene polymers, the preferred Navcom can be formulated so that it will tend to absorb oils. For the present invention, this is a decided benefit. Such absorption keeps skin oils transferred to the ring as disc 20 is handled from migrating from that ring onto the information bearing side 24 of the disc and damaging areas in which information is recorded.

It is believed that the technique employed for detachably assembling ring 22 to disc 20 is apparent from FIG. 1 and from the description of that technique set forth above. To reiterate, however, ring 22 is stretched or distended and slipped over the outer

peripheral edge 34 of disc 20; or, stated conversely, to the extent that the this edge of the disc can be installed in the recess 32 between upper and lower lips 26 and 28 of the ring. This stretching and slipping of the ring over the edge 34 of disc 20 is continued around the circumference of the disc until the ring is completely installed as shown in FIG. 2.

In the representative, illustrated embodiment of ring 22 designed for compact discs, the recess 32 between upper and lower lips 26 and 28 (dimension "w" in FIG. 3) is preferably on the order of 0.07 inch. This is slightly greater than the thickness of a CD and. facilitates the assembly of ring 22 to disc 20 in the manner just described. Ring 22 is dimensioned with its outer circumference 36 approximately equal to the outer diameter 34 of disc 20. Consequently, once ring 22 is installed and released, thereby resulting in its relaxing toward its original configuration and dimensions, the circular rim 30 of the ring will elastically engage the outer periphery 34 of disc 20. This securely holds the ring in place on the ring and makes the use of adheεives and other bonding agents unnecessary. This has the advantage, among others, that ring_22 can be removed easily, and without damaging disc 20, simply by pulling it off the outer edge of the disc.

In the illustrated embodiment of the invention, ring 22 will have a mass in the range of 2-5 grams with this mass uniformly distributed above and below the centerplane 38 of the ring by virture of its symmetrical construction. This added mass is advantageous in that, because of it, an increased

centrifical force is generated as disc 20 is spun to read information therefrom. This increased force tends to keep disc 20 from tilting or fluttering, both of which interfere with the reading of data as the disc is spun. The symmetrical distribution of the ring's mass on both sides of disc 20 also contributes to the stabilization of the disc.

Of course, and as discussed above, the ring is also stabilized by the reduction of the contact area between it and the platter on which it is supported while information is read to a thin annulus and by the ability of the material from which the ring.is formed to deform as necessary into essentially complete contact with the information bearing side 24 of the disc and with the platter on which it is supported.

The invention may be embodied in forms other than those disclosed above without departing from the spirit or essential characteristics of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.