WO2001003134A1

WO2001003134A1 - Irregular shaped compact disc

Info

Publication number: WO2001003134A1
Application number: PCT/AU2000/000728
Authority: WO
Inventors: Ka Ho Tsun
Original assignee: Ka Ho Tsun
Priority date: 1999-07-01
Filing date: 2000-06-28
Publication date: 2001-01-11
Also published as: AUPQ132699A0

Abstract

A compact disc having a shape such that not all parts of the periphery are an equal distance from a centre of the play locating aperture but arranged so as to be balanced. There is also described an arrangement where there are at least two spaced apart portions of the periphery which are an equal distance from the centre of the aperture which enable appropriate location of the disc readily in a receiving tray for insertion into a playing machine.

Description

TITLE

IRREGULAR SHAPED COMPACT DISC

TECHNICAL FIELD

This invention relates to compact discs.

The term "compact disc" in this specification is intended to extend to all types of discs which are currently being used to store data in a digital manner that can be read by a laser based or the like type of reader.

Such discs can be simply referred to also a CD ROM, laser discs, CVD, DVD and cleaning CDs.

Accordingly, reference will be made to compact discs but it is understood that where appropriate this term will include all of the other devices of similar type.

BACKGROUND ART

These devices generally have common features as they currently exist in the commercial market throughout the world namely they have an outermost periphery which is circular and concentric with a central circular co-annular locating aperture which is also round, a reflective pattern beneath a protective surface coat providing a digital data track which is substantially concentric with the locating aperture, and a spacing rim concentric with the locating aperture, which acts to keep compact discs spaced apart.

Conventionally, a compact disc has one side from which the data is read, and the other side is available for printed indicia or other markings appropriate to the content of the data that can be read from the other side.

DISCLOSURE OF THE INVENTION

I have discovered that there is some marketing advantage in having a compact disc which has a periphery which is other than round. If the outer profile shape of a disc can be appropriate to data recorded on the disc, then there can be marketing advantage especially in some markets.

For instance, a compact disc having nursery rhymes recorded, can have the shape of one of the primary characters in the nursery rhyme so that firstly, a child can identify easily the disc without having to rely upon printed indicia, and secondly, a compact disc of the shape say of a Donald Duck or a Mickey Mouse has some marketing appeal when being presented at a retail outlet.

Although the idea of a non-circular periphery of a compact disc would appear reasonably straight forward, it has been found in practice that there are some significant challenges indeed to make such non-round profile compact discs useful as a commercial product for the market.

An objective of this invention then can be said to be to propose a compact disc having a non-round outer periphery which is suitable for the mass market.

A first such problem arises in connection with some but not all mechanisms to which a compact disc is to be located for playing.

Some of these, for instance those devices providing a supporting tray onto which the compact disc is located and then inserted into a cabinet, has an arrangement in which a spindle rises into the locating aperture of the compact disc to then lift this off the supporting tray for rotation and then subsequent reading of the digital data by a laser based device.

Such trays use the periphery shape of a compact disc in order to initially locate the compact disc appropriately for subsequent coincidence of the supporting spindle.

It is highly unlikely that anybody could accurately locate such a compact disc without using the periphery as a location guide so that if the periphery is not circular, then this is where the problem is created.

If the disc then is taken into the mechanism and the spindle does not coincidentally locate the playing locating aperture, then two or three things can happen a first being that the mechanism might jam, a second is that the disc will be partially rotated even though it might not be centrally located and therefore again intersect some parts of the inner mechanism and perhaps either again jam or at least ensnare these, or thirdly, the mechanism will simply not accept the compact disc and in the best case scenario, eject this in a conventional way.

There is a high possibility that the disc will jam within the mechanism and it will be readily understood that this possibility means that such a disc will not be readily saleable on a mass market.

In one form of this invention this can be said to reside in a compact disc which has an outermost periphery which is of a shape such that not all parts of the periphery are an equal distance from a centre of the play locating aperture.

In preference it is further characterized in that the disc has an outermost periphery which is of a shape such that not all parts of the periphery are an equal distance from a centre of the play locating aperture, and either by reason of a balancing weight or weights having been attached or by having an aperture or apertures through a selected part or parts of the disc or by reason of a holder disc adapted to hold the disc, the disc alone or in combination with the holder is balanced to rotate in a balanced manner about the central axis of the locating aperture.

In preference the invention can be further said to reside in a compact disc with a periphery that has all of its periphery at or less than the radius from a centre of a locating aperture of a conventional round compact disc appropriate for the particular player, and there being at least two portions of the periphery which are spaced apart but not so much as to be at locations greater than a radial displacement appropriate for the particular supporting mechanism.

In preference in the case that the disc is not to be held in a holder there are at least two spaced apart portions of the periphery which are an equal distance from the centre of the aperture which enable appropriate location of the disc readily in a receiving tray for insertion into a playing machine.

In preference, these two points are not greater apart than 140° displacement about the centre of the play locating aperture.

This is not to say that there cannot be more parts which are at an equal distance from the centre of the play locating aperture, but that there at least two which thereby provide for a locating guide to locate a non-circular compact disc in a player for playing purposes. The next problem is that when I have tried with a non-circular compact disc, the playing of such a disc even though properly located and being held by an appropriate mechanism, has a substantial tendency to cause noise and vibration.

Further, I have detected in experimental cases, changes in the quality of data for reasons which at first were not apparent.

This difficulty arises, I have discovered, in relation to discs in accordance with this invention, when they are played and do not have their centre of gravity coincident with a centre of the locating aperture about which they are to be rotated.

Devices for capturing and rotating such discs are relatively fragile and are generally susceptible to out of balance forces that might occur if a disc is not balanced. This is especially the case with mechanisms that rotate the disc at higher speeds for instance in some cases now CD ROMs are being played at some 30 times a base speed and no doubt in the future this will be increased significantly.

It is therefore, in preference, a further feature that, in connection with any non- circular shape, there be either an arrangement of the non-planar parts of the disc such that they are symmetrical about the central axis of the locating aperture or there are such shapes or removal of shapes such as to effect a dynamic balancing about the so called central axis of the locating aperture or the disc is adapted to be held with a holder which will rotate with the disc where the holder has corresponding weight distributions such as to effect in combination with the disc, a balanced combined device which together is then adapted to be played as would be the case with a conventional disc.

In this way, I have found that when there is either no or only very minor out of balance forces which will cause the disc when rotating to deviate from the rotational axis and will not subject supporting shafts and bearing to outer unbalance forces which can cause both chatter, in the case that there is some tolerance with relation to relative moving members, or where even when the relatively moving members are fairly accurately fixed.

Such a statement presumes that the central locating aperture is round but if it is not, then it still is necessary for the shape of the aperture to be able to locate onto a supporting shaft so that for purposes of this description, it is the effective centre of such an aperture so that the aperture will hold the disc relative to such a central axis for rotational purposes.

In order for the disc to be able to be properly positioned in relation to a tray, use of the two separate spaced apart points does require that these two spaced apart points are located a distance from a central axis of the locating aperture which is in accordance with the appropriate size of disc for which any receiving tray is designed.

Currently, there are at least three such standards so that typically, the radius might be chosen to match that appropriate for a 40, 60 millimetre disc and the standard radius of the laser disc.

It is also a presumption that the two spaced apart points will be at the maximum radius of any other point located from the central axis of the locating aperture.

When reference is made to the central axis of the locating aperture, this is the axis about which the disc would be expected to rotate when being played.

This ayis then υwnnlH PYtenH πonαrallw at rinht anπloc tn tho πonoral nlnnαr direction of the disc.

Reference is made to a central axis of the locating aperture on the basis that any shape of central locating aperture will be appropriate to engage and hold the disc in an appropriate position for rotation about this axis for playing.

Accordingly, the shape of the central locating axis can be other than circular but it is expected that it would have peripheral points making sure that a spindle appropriate circular shape would engage this aperture appropriately to then locate the disc in this position.

In a further form of this invention this can be said to reside in a method of balancing a compact disc where the compact disc is as previously disclosed , for rotation about its central axis the method including the steps of locating a centre of gravity of the disc, then adding a weight which is positioned so as to be precisely aligned on a line that passes through both the centre of gravity of the disc and a centre of gravity of the weight and the central axis of the disc and selecting a distance from the central axis to bring a resultant centre of gravity to coincide with the rotational axis and moving the weight to this further location.

In a further form in preference there is proposed a method of balancing a compact disc where the compact disc is as previously disclosed herein, for rotation about its central axis, the method including the steps of locating a centre of gravity of the disc, then adding a weight which is positioned so as to be precisely aligned on a line that passes through both the centre of gravity of the disc and a centre of gravity of the weight and the central axis of the disc and selecting a distance from the central axis by calculation or experiment to bring a resultant centre of gravity to coincide with the rotational axis and moving the weight to this further location.

In a further form in preference there is proposed for a compact disc as in previous disclosures herein for rotation about its central axis the method including the steps of locating a centre of gravity of the disc, then adding a weight or weights and moving the weight or weights to this further bringing the centre of gravity of the combination close to the rotational axis of the disc and then treating the combination as a unbalanced disc and the whole disc is balanced with a further weight using the method previously disclosed.

In preference there is a further characterisation wherein the method of balancing a compact disc that is unbalanced at the rotational axis includes the steps of determining the centre of gravity of the unbalanced disc, then causing an aperture through the disc which is positioned so as to be precisely aligned on a line that passes through both the centre of gravity of the unbalanced disc and centre of gravity of the aperture and the central rotational axis of the disc and selecting a distance from the central axis, by calculation or experiment, bringing the resultant centre of gravity to coincide with the rotational axis to effect a counter moment with the weight loss of the aperture to an extent that then effects a balancing of the disc.

In preference there is a method of balancing compact disc as in the immediately preceding paragraph further characterized in that two or more aperture are employed in the balancing including the steps of first effecting an aperture or apertures on the disc at a position that brings the centre of gravity of the combination close to the rotational axis and the combination then being treated as a unbalanced disc and the whole disc is balanced with a further aperture using the method as in the immediately preceding paragraph.

In a further form the invention can be said to reside in a method of balancing a compact disc which is unbalanced about its rotational axis including the steps of determining the centre of gravity of the unbalanced disc, then adding a weight which is positioned so as to be aligned on a line that passes through both the centre of gravity of the unbalanced disc and centre of gravity of the weight and the central rotational axis of the disc and selecting a distance from the central axis, by calculation or experiment using point support or wedge support, to effect a counter moment with the weight to an extent that then effects a balancing of the disc. In calculating the balancing position, the moment formula W x D = w x d is used to determine d, the distance between the centre gravity of the balance weight and the resultant centre of gravity of the combination, in this case the rotational axis. W is the weight of the unbalanced disc, w is the weight of the balance weight, D is the distance of the centre of gravity of the unbalanced disc from the resultant centre of gravity of the combination. The resultant weight of the combination is the sum of the weights of the unbalanced disc and the balance weight, W + w, and lies between the two centre of gravity of the unbalanced disc and the balance weight.

In a further form the invention can be said to reside a method of balancing compact disc as in the immediately preceding paragraph further characterized in that two or more weights are employed in the balancing includes the steps of first adding weights one by one on the disc at a position that brings the centre of gravity of the combination close to the rotational axis and the combination is treated as a unbalanced disc. Method and formula described in the immediately preceding paragraph are employed in the process to determine the resultant centre of gravity and weight and the last balance weight is added to effect a rotational balance disc.

In a further form the invention can be said to reside in a method of balancing a compact disc that is unbalanced at its rotational axis including the steps of determining the centre of gravity of the unbalanced disc, then having a aperture which is positioned so as to be aligned on a line that passes through both the centre of gravity of the unbalanced disc and centre of gravity of the aperture and the central rotational axis of the disc and selecting a distance from the central axis, by calculation or experiment using point support or wedge support, bringing the resultant centre of gravity to coincide with the rotational axis to effect a counter moment with the weight loss of the aperture to an extent that then effects a balancing of the disc.

In calculating the balancing position, the material removed form the aperture represents the aperture and the moment formula W1 x D1 - w1 x d1= 0 is used to determine d1 , the distance between the centre gravity of the aperture, and the resultant centre of gravity of the combination, in this case the rotational axis. W1 is the weight of the unbalanced disc, w1 is the weight of the aperture material removed, D1 is the distance of the centre of gravity of the unbalanced disc from the resultant centre of gravity of the combination. The resultant weight of the combination is the difference of the weights of the unbalance disc and the balance weight, W1 - w1 , and is outside the line joining the two centre of gravity of the unbalanced disc and the aperture.

In a further form the invention can be said to reside in a method of a balancing compact disc as in the immediately preceding paragraph further characterized in that two or more apertures are employed in the balancing includes the steps of first making apertures one by one on the disc at a position that brings the centre of gravity of the combination close to the rotational axis of the disc and then applying the method to the combination so that this is then treated as an unbalanced disc.

In preference the method and formula described in the preceding paragraphs are employed in the process to determine the resultant centre of gravity and weight and a last aperture is added to effect a final rotational balance disc.

In a further form the invention can be said to reside in a method of balancing a compact disc that is unbalanced at the rotational axis which employs more than one of the methods described in the previous paragraphs.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention will now be obtained by reference to embodiments which will be described with the assistance of the accompanying drawings in which:

FIGURE 1 : is a plan view of a typical compact disc illustrating a central locating aperture 1 and outer most circular periphery 2 and there being an outermost uppermost surface 3 which is planar and on which conventional literature such as the name of the work or other label material is printed,

FIGURE 2: is a plan view of a conventional compact disc from the side opposite that shown in FIGURE 1 with again the outer periphery being circular and being concentric with the inner locating aperture 1 of circular peripheral shape, the outer periphery being circular at 2 and there being an area on the underneath side which is shown as 3 which is concentric with the circular aperture 1 and in which there is the track in which digital data is recorded,

FIGURE 3: is a tray of the type on which a conventional compact disc or a CD ROM is to be located so that the tray 4 can then revert back to within a reading device for playing,

FIGURE 4: is a view of the tray as in FIGURE 3 with the conventional compact disc as shown in FIGURES 1 and 2 located therefore insertion as a part of the tray into a playing position within the apparatus,

FIGURES 5, 6 and 7: are views respectively from an upper face, a lower face and a perspective of the upper face of a compact disc of different peripheral shape,

FIGURES 8, 9 and 10: illustrate a further compact disc of similar shape to that shown in FIGURES 5, 6 and 7 except that it is of lesser peripheral dimensions,

FIGURE 11 : illustrates the disc of FIGURES 5, 6 and 7 being placed in position on the tray 4,

FIGURE 12: illustrates the positioning of the example of FIGURES 8, 9 and 10 on the tray 4,

FIGURE 13: illustrates the locating of the example as in FIGURES 8, 9 and 10 being located above a holder,

FIGURE 14: is an illustration of the underneath side of the compact disc as shown in figure 13 actually in position and being held by a holder, FIGURES 15 and 16: illustrate a further way in which a disc is to be position and held within a holder,

FIGURES 17 and 18: illustrate how a holder as shown in combination in FIGURES 14 and 16 are turned over and are located in the ordinary manner in a tray for insertion into a playing unit,

FIGURE 19: is an angled view looking down into the holder from the bottom plan with the dotted outline showing a disc in the holder,

FIGURE 20: is an angled view showing other sized discs being balanced in the holder,

FIGURE 21 : is an angled view of the bottom plan of the disc and the holder,

FIGURE 22: is the view of FIGURE 19 when the disc and holder are joined,

FIGURE 23: is an angled view of the non functional face of a balanced disc,

FIGURE 24: is a further example of a disc in this case having apertures at the three apexes of the club shape to provide for additional artistic appearance and to also assist in balance,

FIGURE 25: is an angled view of the readable digital data face of a balanced disc,

FIGURE 26: illustrates a holder with holes providing balancing and centreing features for the unbalance disc as in FIGURE 8,9 and 10,

FIGURE 27: illustrates how the unbalanced disc as in FIGURE 8, 9 and 10 can be located within a holder of FIGURE 26 which of itself is then balanced,

FIGURE 28: is a further arrangement as in FIGURE 26 but for a larger periphery dimension for the unbalance disc as in FIGURE 5,6 and 7,

FIGURE 29: is a bottom plan of FIGURE 27, FIGURE 30: is a perspective view looking down into a universal holder with a balance weight,

FIGURES 31 and 32: illustrate a further outermost peripheral shape in this case the map of Australia where there are five points spaced apart by which the disc can be located within the tray 4,

FIGURE 32: is an angled view of FIGURE 31 ,

FIGURE 33 and 34: illustrate a further embodiment in which there are three dimensional protrusions from the otherwise planar shape,

FIGURE 35: illustrate the CD in FIGURE 33 and 34 in tray 4 using its two outer portions for aligning its centre to that of the tray depression,

FIGURE 36: is an angled view looking down at the non-circular disc being placed on a single support point with a balanced blank infill,

FIGURE 37: is an angled perspective of FIGURE 36 and with the CD placed on the blank infill,

FIGURE 38: is a side plan view of FIGURE 37,

FIGURE 39 - 42: illustrate how a weight can be attached and provide dynamic balance to allow for the disc to operate reasonably within conventional equipment for playing purposes, while FIGURE 41 having a balance weight on the side opposite to that containing the readable digital data and FIGURE 42 having a balance weight on the side that containing the readable digital data,

FIGURES 43 - 46: illustrate the same set of balancing procedures for this further embodiment,

FIGURE 47: illustrates the embodiment as shown in FIGURES 39-42 as to how this would be then positioned positively within a tray for insertion into a playing device and the entire combination is rotational balanced for playing. FIGURE 48 - 51 : show another three different methods in locating the centre of gravity of a non-circular CD, while FIGURE 49 is a side plan view of FIGURE 48, and FIGURE 50 is a top plan view of the centre of gravity taken with a pendulum, and FIGURE 51 : is an angled view of the centre of gravity taken with a knife edge.

FIGURE 52: is a top plan view of the non-circular disc,

FIGURE 53: is an angled perspective of FIGURE 52,

FIGURE 54: is a side plan view of FIGURE 53.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the drawings in detail, as previously referred to, the prior art is illustrated in the examples of FIGURES 1-4.

In particular, the tray 4 is shaped so that the distance between points 5 and 6 are such that if joined by a radial line from a virtual centre position at 7, the angle between the two radii will be approximately 140 degrees.

The gap 8 is used when the tray 4 in a playing position for travel of a laser reading device. In the first example which is a first embodiment shown in FIGURES 5, 6 and 7, the lobes of the club shape of the disc having a non circular outermost periphery are positioned so that the outer most peripheral points at 10, 11 and 12, will define with an axial centre at 13 of the locating aperture 14 a radius which is equal to the radius of a standard compact disc which is to say 60 millimetres and the angle 15 between radius lines 16 and 17 is 130 degrees which is to say modestly less than 140 degrees which is the angle subtended by the points 5 and 6 on the tray 4 back in FIGURES 3 and 4.

In this way, with an underneath side having a concentric angular area 18 to provide for digital data to be read, this disc can be readily positioned by hand in the tray 4 simply by pulling back on the lobes so that they engage against the circular edge of the tray so that the positioning of the disc is then going to be aligned so that the locating aperture 14 will be accurately aligned when the tray is in a playing position.

FIGURE 6 shows the reverse view with the concentric area 18 with the central axis 13 of the locating aperture 14.

The only difference between the examples shown in FIGURES 5, 6 and 7 and 8, 9 and 10 is that the overall relative size of the disc is smaller so that while there is still room for a concentric portion on the underneath side shown at 19 of the disc 20 nonetheless, the distance from the central axis in this case 21 to a most distal portion of a lobe such as at 22 will be less than the radius of a conventional compact disc.

This is most clearly shown in FIGURES 11 and 12 where in FIGURE 12, there is a gap of a significant extent shown for instance at 23 and 24 so that there would be difficulty in locating such a disc as is shown at 25 in connection with the tray 4.

In this case then, as is shown in FIGURES 13 - 16, there can be a holder as is shown at 26 in which there is a recess 27 which matches the shape of the disc portion at 25 and there are slight protruding parts such as at 28 typically so that the disc 25 will in effect be held in the holder 26 by relative compression.

There are coincident alignments of a central location aperture in the holder at 30 and in the compact disc at 31.

In another way of locating a compact disc such as at 32 in FIGURE 15, there are apertures such as at 33 which coincide with fingers such as at 34 where again, the disc will then be held by relative compression between the closely nesting parts.

When turned over as shown in FIGURES 17 and 18, the disc then operates as a normal disc shown at 35 and will locate as normal within a tray 4.

FIGURE 19 is a perspective view of a composite disc where the holder 40 holds within it a club shaped disc 41 but in this case there is provided the further feature of a balancing weight at 42.

Because there is clearance when disc is played, such a weight can be attached externally and protrude slightly from one side or the other.

FIGURE 20 is a perspective view along the same lines as in FIGURE 19 but in this illustration it can be appreciated that the holder has the scope to accommodate other disc sizes 43. Looking at FIGURE 19 from a bottom perspective as in FIGURES 21 and 22 it is clear that the holder can correctly align the disc and also through the weight precisely balance it.

FIGURES 23-25 provide still further methods to correctly balance a non circular disc. The balance weight can be located on either the non functional face 44 or the readable digital data face 45. In some instances weight can be located on both sides simultaneously or in a depression or an aperture through the disc. FIGURE 24 shows how apertures 46 strategically located provide additional artistic appearance but also assist in balancing.

Similarly, as illustrated in FIGURES 26-29 the apertures 46 contributing to balance can be apart of the holder. This kind of holder like the ones in FIGURES 19 and 20 can accommodate different sizes of discs. FIGURE 27 is showing the disc being placed on a holder 48 which has itself apertures which provide the balance and the alignment of the disc.

A better appreciation of the apertures can be found by viewing the bottom plan of the holder as in FIGURE 29.

FIGURE 30 illustrates an adjustable universal holder with a method of balance which can be used in conjunction with an unbalanced compact disc, having an adjustable weight 49 that can be positioned to achieve balance both in distance from a centre and in relation to an angular orientation using a grid 51 according to a description or label on the disc.

FIGURES 31 -32 Drovide a detailed descrintion of how the niitermnst nerinheral shape 52a, 52b, 52c, 52d and 52e of a non circular disc can be designed so as to readily align itself in the tray depression 4 of a disc player. In this case a map of Australia 51 is used for demonstration purposes only, the concept could be just as easily applied to any shape.

FIGURES 33-34 can be an extension or independent of FIGURES 31 and 32 where three dimensional extrusions 52 protrude from the plan of the disc for aesthetic and balancing reasons. FIGURE 35 shows the disc in FIGURES 33 and 34 being place in a CD player tray 4.

FIGURES 36-40 illustrate a balancing technique. An unbalanced disc is put on a balanced blank infill 55 which sits on a single support point 53 at its centre. The whole combination being unbalanced will slope to one side as shown in FIGURES 37 and 38. The balance method is achieved by adding an appropriate weight 56 on to and then moving this around the disc until the whole combination will remain horizontal as shown in FIGURES 39 and 40. The same balance weight can then be added to the non-functional side 57 or the side 58 with readable digital data at the location which was previously found to balance the combination to thereby form a rotational balanced disc as illustrated in FIGURES 41 and 42. This then is a method of balancing an otherwise unbalanced compact disc which includes the steps of determining a centre of gravity of the unbalanced disc, then adding the weight and positioning this so as to be precisely aligned on a line that passes through both the centre of gravity and a central axis of the disc and selecting a distance from the central axis to effect a counter moment with the weight to an extent that then effects a balancing of the disc.

In practise the distance can be judged and then by trial and error corrected by very small amounts until an accurate balance is achieved in a static way which is then found to translate to a dynamic result.

FIGURES 43-46 illustrate the same method as in FIGURES 39 - 40 using the map of Australian in FIGURES 33 - 35. Three dimensional protrusions 52 are used as balance weights to balance the disc as well as adding artistic appearance. FIGURE 46 shows the side 58 of the disc with the readable digital data and a balance weight can be added to this side if required.

FIGURE 47 illustrates the balance disc in FIGURE 41 being put in a CD player tray 4.

FIGURES 48 - 51 illustrate three other methods to balance a unbalanced compact disc by first locating the centre of gravity 59 of the unbalance disc. A single supporting point is used in FIGURES 48 and 49. A pendulum 61 is used in FIGURE 50 and a knife edge 62 is used in FIGURE 51. To achieve rotational balance, a portion, say a hole 60, can be cut from the disc and the centre of gravity of this shape lies on the line joining the centre of the central aperture and the centre of gravity 59 of the unbalance disc. The position of the shape depends on the size of the shape and the weight of the unbalance disc and is to be calculated out as shown in FIGURE 52.

The balanced disc can then be tested to be balance by putting it on a balanced blank infill resting on a single support point at its central axis and the whole combination is horizontal as in FIGURES 53 and 54.

Results of tests conducted to establish that these arrangements are useful.

A first standard compact disc was tested in a vibration test apparatus namely Bruel &Kjaer Multi-analyser system 3560, Data acquisition Unit 2827 and a Armada 4120T laptop CD-ROM drive. Irregular shape compact discs that were used in the tests were balanced using the aforesaid instructions with balance weights being inserted in holes drilled through the discs at the corresponding positions.

The first harmonic was found to occur at 50 Hz and the following results were found when taken at this frequency.

Degree of out of balance for the standard CD is 24mg

Irregular shaped CD 1 (Max)

Before being balanced in accord with the instruction above is 107mg. After being balanced as per the above instructions is 30 mg.

Irregular shaped CD 2 (Andy Lau) before balanced in accord with the instruction above is 120mg.

After being balanced as per the above instructions is 5 mg.

Irregular shaped CD 3 (Leon) before balanced in accord with the instruction above is 70mg.

After being balanced as per the above instructions ]s 5 mg.

These results show that this simple centre of gravity determination is adequate to give sufficient balance for use of otherwise substantially unbalanced CD's.

Claims

1. A compact disc which has an outermost periphery which is of a shape such that not all parts of the periphery are an equal distance from a centre of the play locating aperture.

2. A compact disc as in claim 1 further characterized in that the disc either by reason of a balancing weight or weights having been attached or by having an aperture or apertures through a selected part or parts of the disc or by reason of a holder disc adapted to hold the disc, alone or in combination with the holder is balanced to rotate in a balanced manner about a central axis of the play locating aperture.

3. A compact disc as in claim 1 further characterized in that there are at least two spaced apart portions of the periphery which are an equal distance from the centre of the aperture which enable appropriate location of the disc readily in a receiving tray for insertion into a playing machine.

4. A compact disc as in any one of the preceding claims further characterized in that it has all of its periphery at or less than the radius from a centre of a locating aperture of a conventional round compact disc appropriate for an appropriate player, and there are at least two portions of the periphery which are spaced apart but not so much as to be at locations greater than a radial displacement appropriate for a selected supporting mechanism.

5. A compact disc as in the immediately preceding claim further characterized in that the said two points are not greater apart than 140° displacement about the centre of the play locating aperture.

6. A compact disc as in any one of the preceding claims further characterized in that there is an arrangement any of the non-planar parts of the disc such that they are symmetrical about the central axis of the locating aperture.

7. A compact disc as in any one of the preceding claims further characterized in that there are such shapes or removal of shapes such as to effect a dynamic balancing about the so called central axis of the play locating aperture.

8. A compact disc as in any one of the preceding claims further characterized in that the disc is adapted to be held with a holder which will rotate with the disc where the holder has a cooperating weight distribution such as to effect in combination with the disc, a balanced combined device which together is then adapted to be played as a circular periphery conventional disc.

9. A compact disc as in any one of the preceding claims further characterized in that the two spaced apart points will be at a radius which is at least the same as any other point located from the central axis of the locating aperture.

10. A method of balancing a compact disc where the compact disc is as in any one of the preceding claims, for rotation about its central axis the method including the steps of locating a centre of gravity of the disc, then adding a weight which is positioned so as to be aligned on a line that passes through both the centre of gravity of the disc and a centre of gravity of the weight and the central axis of the disc and selecting a distance from the central axis to bring a resultant centre of gravity to coincide with the rotational axis and moving the weight to this further location.

11. A method of balancing a compact disc where the compact disc is as in any one of the preceding claims 1-9, for rotation about its central axis the method including the steps of locating a centre of gravity of the disc, then adding a weight which is positioned so as to be aligned on a line that passes through both the centre of gravity of the disc and a centre of gravity of the weight and the central axis of the disc and selecting a distance from the central axis by calculation or experiment to bring a resultant centre of gravity to coincide with the rotational axis and moving the weight to this further location.

12. A method of balancing a compact disc where the compact disc is as in any one of the preceding claims 1-9, for rotation about its central axis the method including the steps of locating a centre of gravity of the disc, then adding a weight or weights and moving the weight or weights to this further bringing the centre of gravity of the combination close to the rotational axis of the disc and then treating the combination as a unbalanced disc and the whole disc is balanced with a further weight using the method as in either one of the immediately preceding claims 10 or 11.

13. A method of balancing a compact disc that is unbalanced about its rotational axis including the steps of determining the centre of gravity of the unbalanced disc, then causing an aperture through the disc which is positioned so as to be aligned on a line that passes through both the centre of gravity of the unbalanced disc and centre of gravity of the aperture and the central rotational axis of the disc and selecting a distance from the central axis, by calculation or experiment, bringing the resultant centre of gravity to coincide with the rotational axis to effect a counter moment with the weight loss of the aperture to an extent that then effects a balancing of the disc.

14. A method of balancing compact disc as in the immediately preceding claim further characterized in that two or more aperture are employed in the balancing including the steps of first effecting an aperture or apertures on the disc at a position that brings the centre of gravity of the combination close to the rotational axis and the combination then being treated as a unbalanced disc and the whole disc is balanced with a further aperture using the method as in the immediately preceding claim 13.

15. A compact disc resulting from a combination of more than one of the methods as set out in any one of the preceding claims 10 through 14.

16. A method of desiαninα a comDact disc which includes the method as set out in any one of preceding claims 10 through 15 and then replicating compact discs in accord with that design.