Abstract:
A disk for a disk drive including a disk body with a center through hole for fixing the disk body to a turntable formed at a center thereof, a clamping portion formed on the disk body around the center through hole to fix the disk body to the turntable, a signal recording portion which is formed on a surface of the disk body around a rim of the clamping potion and includes a signal recording section on which digital signals are recorded, and crack blocking portions bored through the clamping portion.

Description:
This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 10-2003-0075642 filed in Korea, Republic of on Oct. 28, 2003, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates to a disk for a disk drive, and more particularly, to a disk, at least one surface of which is provided with a signal recording portion to record and reproduce signals in a disk drive. 
   2. Description of the Prior Art 
   Disks (for example, CDs or DVDs) are used as media for recording and reproducing digital data. The recording and reproduction of the digital data in the disk is performed in a disk drive.  FIG. 1  shows a plan view of the disk according to a prior art. 
   As shown in the figure, a disk  10  comprises a disk body  12  shaped in a circular disk. The center of the circular disk body  12  is formed with a center through hole  14 . The center through hole  14  with a predetermined diameter is bored through the center of the disk body  12 . 
   The center through hole  14  is fitted onto an insertion cone provided on a turntable of the disk drive. That is, an inner peripheral surface of the center through hole  14  is fitted onto an outer peripheral surface of the insertion cone. 
   A clamping portion  16  with a predetermined width is formed around the center through hole  14 . A lower surface of the clamping portion  16  is seated onto the turntable. A clamp for fixing the disk  10  to the turntable is seated onto an upper surface of the clamping portion  16 . In a case where in the disk drive, the insertion cone is provided with the clamp, the upper surface of the clamping portion  16  is not naturally used for the disk to be clamped. 
   A signal recording portion  18  ranges from an outside of the clamping portion  16  to a rim of the disk body  12 . The signal recording portion  18  is provided with a signal recording section  19 , inner and outer rims of which are formed with inner and outer rim sections  20  and  20 ′, respectively. The inner rim section  20  is a boundary between the clamping portion  16  and the signal recording section  19 . 
   However, the above prior art has the following problems. 
   That is, as shown in  FIG. 2 , in the conventional disk  10 , cracks c occur on an outer rim of the center through hole  14 . This is the reason why a force may be applied thereto while a friction is generated between the outer rim of the center through hole  14  and the insertion cone in a process of seating and separating the disk  10  onto and from the turntable. Particularly, in a case where the insertion cone has the structure for clamping the disk  10 , the cracks c easily occur. 
   In addition, as the speed of the disk drive has been recently increased at a high multiple access speed, the rotation rate of the disk  10  generally increases to 8,000 rpm or more. However, if the rotation rate of the disk  10  increases, causing a centrifugal force to increase, the cracks occurring on the outer rim of the center through hole  14  gradually propagate up to the signal recording portion  18 . In a severe case, it may be possible not to use the disk since the disk body  12  is completely broken. Furthermore, some broken pieces of the broken disk body  12  spatter outward, so that users may be injured. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a disk for a disk drive wherein cracks occurring on the disk cannot be prevented from propagating beyond a predetermined range. 
   According to an aspect of the present invention for achieving the objects, there is provided a disk for a disk drive, comprising a disk body with a center through hole for fixing the disk body to a turntable formed at a center thereof; a clamping portion formed on the disk body around the center through hole to fix the disk body to the turntable; a signal recording portion formed on a surface of the disk body around a rim of the clamping portion and including a signal recording section in which digital signals are recorded; and crack blocking portions bored through the clamping portion. 
   Preferably, the crack blocking portions comprises circular through holes. 
   More preferably, the crack blocking portions comprises slot shaped through holes with a predetermined curvature. 
   An outer side section of a contour of each of the slot shaped through holes is formed in a curved line and is longer than an corresponding inner side section thereof. 
   The contour of each of the slot shaped through holes is formed in curved lines. 
   The crack blocking portions are arranged in circles, and the crack blocking portions arranged in a relatively inner circle and the crack blocking portions arranged in a relatively outer circle are arranged in a zigzag pattern. 
   A coating layer is formed on surfaces of the clamping portion in which the crack blocking portions are formed, or heat treatment is performed thereon. 
   According to the disk for the disk drive of the present invention so constructed, there is an advantage in that cracks occurring on an outer rim of the center through hole do not propagate up to the signal recording portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a plan view showing a disk for a disk drive according to a prior art; 
       FIG. 2  is a view illustrating a problem of the disk according to the prior art; 
       FIG. 3  is a plan view showing a preferred embodiment of a disk for a disk drive according to the present invention; 
       FIG. 4  is a plan view showing another embodiment of the present invention; 
       FIG. 5  is a plan view showing an additional embodiment of the present invention; and 
       FIGS. 6   a  to  6   c  are views showing that the embodiments of the present invention prevent cracks from further propagating. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Hereinafter, preferred embodiments of a disk for a disk drive according to the present invention will be described in detail with reference to the accompanying drawings. 
     FIG. 3  is a plan view showing a preferred embodiment of a disk for a disk drive according to the present invention. 
   As shown in the figure, a disk  30  of the embodiment of the present invention consists of a disk body  32  shaped in a circular disk. The center of the disk body  32  is formed with a center through hole  34  concentrically with the disk body  32 . An insertion cone provided in a turntable of the disk drive is seated into the center through hole  34  when seating the disk  30  on the turntable. An outer diameter of the insertion cone is formed to be the same as or slightly smaller than an inner diameter of the center through hole  34 . 
   A clamping portion  36  is formed to extend over a predetermined width from the center through hole  34  toward a circumference of the disk body  32 . The clamping portion  36  is a portion which is seated on the turntable. Particularly, a surface of the clamping portion  36  corresponding to a lower surface of the disk body  32  is seated on the turntable. 
   In addition, according to the kind of the disk drive, a clamp is seated on the opposite surface of the clamping portion  36  corresponding to an upper surface of the disk body  32 . In a general slim disk drive, the insertion cone is provided with a structure for clamping the disk, so that an outer rim of the center through hole  34  is used for clamping the disk. 
   A signal recording portion  38  ranges from an outside of the clamping portion  36  to a rim of the disk body  32 . The signal recording portion  38  is provided with a signal recording section  39  with a predetermined width in which digital data are recorded. Inner and outer rims of the signal recording section  39  are formed with inner and outer rim sections  40  and  40 ′ with predetermined widths, respectively. The inner rim section  40  is a boundary between the signal recording section  39  and the clamping portion  36 . 
   In the meantime, the clamping portion  36  is formed with crack blocking portions  42 . In the present embodiment, each crack blocking portion  42  is shaped in a circular through hole. A plurality of the crack blocking portions  42  are bored through the clamping portion  36 . The plurality of the crack blocking portions  42  are arranged in circles. 
   In the present embodiment, the crack blocking portions  42  are arranged to substantially form two circles. At this time, any one of the crack blocking portions  42  arranged in the relatively inner circle and any one of the crack blocking portions  42  arranged in the relatively outer circle are not formed on the same radial line of the disk body. 
   That is, the crack blocking portions  42  arranged in the relatively inner circle and the crack blocking portions  42  arranged in the relatively outer circle are formed in a zigzag pattern, i.e. in a staggered fashion. It is intended for the crack blocking portions  42  arranged in the relatively outer circle to block cracks c although the cracks c propagate through between the crack blocking portions  42  arranged in the relatively inner circle. In practice, it is preferred that the number of the circles formed by the crack blocking portions  42  be large in the case where each crack blocking portion  42  is formed in the circular through hole. 
   In the meantime,  FIG. 4  shows another embodiment of the present invention, wherein for convenience of description, only different portions from the previous embodiment will be described and reference numerals increased by one hundred are given to the same elements as the previous embodiment. 
   In the present embodiment, crack blocking portions  142  each of which is shaped in a slot with a predetermined curvature is bored through a clamping portion  136 . That is, each crack blocking portion  142  is formed so that a difference between radii of its inside and outside curved sections  143  and  143 ′ from the center of a disk body  132  is the same as a width of the slot, i.e. the crack blocking portion  142 . Alternatively, the inside and outside curved sections  143  and  143 ′ may be formed to differ from each other in center of curvature. 
   A plurality of the crack blocking portions  142  are also arranged in circles, wherein the number of the circles formed by the crack blocking portions  142  is two in the present embodiment. In addition, the crack blocking portions  142  in the relatively inner circle and the crack blocking portions  142  arranged in the relatively outer circle are formed in a zigzag pattern. Therefore, it is possible for the crack blocking portions  142  in the relatively outer circle to block the cracks c although the cracks c propagate after passing between the crack blocking portions  142  arranged in the relatively inner circle. 
   Next,  FIG. 5  shows an additional embodiment of the present invention. In the present embodiment, crack blocking portions  242 , each of which is shaped in a slot with a predetermined curvature, are bored through a clamping portion  236 . In the present embodiment, a contour of each crack blocking portion  242  consists of curved lines as shown in  FIG. 5 . 
   In addition, even in the present embodiment, a plurality of the crack blocking portions  242  are arranged in the clamping portion  236  in two circles, which are formed relatively inside and outside, respectively. Furthermore, the crack blocking portions  242  arranged in the relatively inner circle and the crack blocking portions  242  arranged in the relatively outer circle are also arranged in a zigzag pattern. 
   In the meantime, in the embodiments described above, coating layers may be separately formed on surfaces of the clamping portions  36 ,  136 , and  236  in which the crack blocking portions  42 ,  142 , and  242  are formed, or heat treatment may be performed thereon. By forming the coating layers or performing the heat treatment on the clamping portions  36 ,  136 , and  236 , it is possible to reinforce strength, which may decrease since the crack blocking portions  42 ,  142 , and  242  are formed. 
   Hereinafter, an operation of the disk for the disk drive according to the present invention so constructed will be described. 
   In the present invention, by forming the crack blocking portions  42 ,  142 , and  242  in the clamping portions  36 ,  136 , and  236 , which correspond to peripheral portions of the center through holes  34 ,  134 , and  234  of the disks  30 ,  130 , and  230 , the cracks c occurring on the rims of the center through holes  34 ,  134 , and  234  are prevented from propagating up to the signal recording portions  38 ,  138 , and  238 . 
   That is, as shown in  FIGS. 6   a  to  6   c , when the cracks c occurring on the rims of the center through holes  34 ,  134 , and  234  further propagate by the centrifugal forces caused from the rotations of the disks  30 ,  130 , and  230  or external forces applied to the disks  30 ,  130 , and  230 , the cracks c propagate no more if they meet the crack blocking portions  42 ,  142 , and  242 . 
   The phenomenon that the cracks c stop propagating when meeting the crack blocking portions  42 ,  142 , and  242  is due to stress concentration. That is, once the cracks c occur, the cracks c further propagate while stresses are concentrated at distal ends of the cracks c. However, if the cracks c meet the crack blocking portions  42 ,  142 , and  242 , the stresses are dispersed around the rims of the crack blocking portions  42 ,  142 , and  242 , and thus, the cracks c are prevented from further propagating. 
   Particularly, if angled portions are not formed in edges of the crack blocking portions  42 ,  142 , and  242  and the edges are generally shaped in curved lines, the above effect more increases. In the embodiment shown in  FIG. 4 , although both ends of each crack blocking portion  142  are formed with angled portions, since the outside curved section  143 ′ of the crack blocking portion  142  is relatively long, the cracks c cannot propagate toward the signal recording portion  39  once meeting the crack blocking portion  142 . 
   In the meantime, even if the cracks c pass between the crack blocking portions  42 ,  142 , and  242  arranged in the relatively inner circles, the cracks c propagate no more by means of the crack blocking portions  42 ,  142 , and  242  arranged in the relatively outer circles. 
   As described above in detail, the disk for the disk drive according to the present invention is configured so that the clamping portion of the disk body is formed with the crack blocking portions. 
   Therefore, even if the cracks occur on the rim of the center through hole of the disk body, by means of the crack blocking portions, the cracks are blocked from propagating, so that the signal recording portion or disk body can be prevented from damaging or breaking. 
   Particularly, even if the rotation rate of the disk and therefore the centrifugal force increase in a high multi-speed disk drive, an advantage of preventing the cracks occurring from further propagating can be expected. 
   In addition, by forming the coating layers or performing the heat treatment on the clamping portion, it is possible to reinforce the strength, which may relatively decrease. 
   The scope of the present invention is not limited to the embodiments described and illustrated above but is defined by the appended claims. It will be apparent that those skilled in the art can make various modifications and changes thereto within the scope of the invention defined by the claims. Therefore, the true scope of the present invention should be defined by the technical spirit of the appended claims. 
   For example, the shape of the crack blocking portion may be variously modified in addition to those described in the present embodiments.