The present invention relates to flexible data storage cards. More particularly, it relates to a method of manufacturing media reference surfaces for use in a flexible data storage card such as a StorCard® flexible data storage card.
Data storage media have been used for decades in the computer, audio, and video fields. Data storage media continue to be employed for storing large volumes of information in a form suited for subsequent retrieval and use.
Data storage media are generally provided in one of two forms, long strands of tape and rotating discs. The rotating disc data storage media are generally of two types: hard disc (HD) media and floppy disc (FD) media. Generally, HD media are maintained within a housing of a data storage device and is associated with a drive, neither of which is removable from the housing. For example, HD media are commonly maintained within a computer hard drive and accessed via an internal read/write device of the drive. In contrast, FD media are removable from, and interchangeable between, data storage devices. In this regard, FD media have the benefit of being transportable. Typically, a shutter is provided on an exterior portion of the FD to cover and protect the FD media during periods of inactivity and to permit the read/write device to access the FD media during use.
HD media employ rigid discs formed of a metal substrate and include a sputter deposition of a magnetic film. Deposition of the magnetic media in this manner permits a very high magnetic recording density to be achieved. During a read/write operation, the HD media are rotated at high speeds and “fly” over the read/write head in a non-contact manner. In contrast, the FD media are composed of a plastic substrate, such as Mylar®, which is coated with a slurry of magnetic particles. In this regard, FD media operate at low speeds and the read/write head contacts the recording medium. To facilitate good wear characteristics, the magnetic slurry contains a binder and a bulk lubricant along with the magnetic particles. Regardless, FD media is typically provided to users in an industry-accepted format, such as 3.5 inch floppy discs. While universally accepted, these formats are not conducive to convenient handling and carrying by users, have limited storage capacity, and do not provide rigorous protection for the FD media.
More recently, efforts have been made to provide a conveniently sized, robust FD-type media. In particular, flexible media are fabricated into a disc and placed within a transportable card having a form factor of approximately that of a credit card. Such a device is known as a “flexible data storage card” and has mechanical flexibility in both the longitudinal and transverse directions. A flexible data storage card described by StorCard, Inc., San Jose, Calif. under the trademark StorCard® is one example. Generally, the StorCard® flexible data storage card consists of an outer shell or housing that maintains the flexible media disc. The housing normally includes a separate cover and a separate base that encloses the flexible media, fabric liners, and other components. The cover is known as a card top and is formed of a plastic laminate and includes an integrated circuit that monitors the flow of data into, and out of, the flexible storage card. The base is a thin metallic structure that is laminated to the card top to form the housing structure. A window is provided on the base and includes a shutter that provides selective access to the flexible media disc by an external read/write head.
During use, the shutter in the base is displaced to provide access to the flexible media disc by the read/write head. The flexible media disc rotates at approximately 3600 rotations per minute (rpm) thereby attaining a high velocity at the edge of the disc. The high velocity of the rotating disc is desirable and creates an “air bearing” between the flexible media disc and the read/write head. In this regard, the read/write head is said to “fly” over the flexible media disc. The air bearing is comprised of aerodynamic forces that can be controlled to ensure that the read/write head does not “crash” into the flexible media disc, as such contact could lead to catastrophic damage to the flexible media disc and the data stored thereon. To assist in the positioning of the read/write head and the flexible media disc, a media reference surface is provided on the interior side of the card top in a position opposite the shutter/window of the base (i.e., opposite of the read/write head).
The media reference surface is generally an elongated piece of non-magnetic metal attached to the card top interior. In particular, the media reference surface is situated adjacent the side of the flexible media that is not coated with magnetic media. Positioned in this manner, the flexible media disc “flies” between the read/write head and the media reference surface during a read/write operation such that air bearings are formed between both the read/write head and the disc and the media reference surface and the disc. Consequently, the side of the media reference surface exposed to the disc must have a very smooth surface topography to ensure that the air bearings are not disturbed. Additionally, because the disc flies over the media reference surface, the leading edge of the media reference surface is preferably rounded, or curved, to avoid the possibility of the media reference surface cutting into, or skiving, the disc.
Prior art media reference surfaces, and in particular those associated with StorCard® products, are first formed to the desired size and then the exposed surface (i.e., the disc side) is polished by hand. During polishing, the leading edge of the media reference surface is rounded. This high polish finish is characterized by an average surface roughness (Ra) as measured in micro-inches. Typically, the media reference surface will have an Ra of not greater than 8.0 micro-inch and a rounded leading edge having a radius of curvature on the order of 0.005 inch. These surface features are carefully crafted onto each prior art media reference surface consuming large spans of time. Accordingly, the known media reference surfaces are hand finished and are characterized by a low throughput rate that is associated with one-piece-at-a-time hand finishing. As such, the media reference surface component of a StorCard® flexible data storage card, or other flexible data storage card, has a comparatively high component cost and limits the production rate of these data storage devices. For these reasons, a need exists for a method of manufacturing media reference surfaces without hand polishing.
One aspect of the present invention relates to a method of manufacturing media reference surfaces for use in a flexible data storage card. The method includes providing a metal sheet having a first side and a second side, at least one side having an optically smooth surface characterized by an average surface roughness not greater than 8 micro-inch. The method additionally includes processing the metal sheet into a plurality of media reference surfaces such that each media reference surface has at least one curved edge adjacent the optically smooth surface. In this regard, the processing is characterized by the absence of hand polishing.
An additional aspect of the present invention relates to another method of manufacturing a media reference surface for use in a flexible data storage card. This method includes providing a source of metal sheeting, the metal sheeting having a first side and a second side, at least one side having an optically smooth surface. The method additionally includes shearing the metal sheeting with a die and a punch to form the media reference surfaces such that each media reference surface has a leading edge and a trailing edge. The shearing is configured to die roll at least the leading edge.
Embodiments of the invention are better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
The present invention relates to a method of fabricating a media reference surface for use in a flexible data storage card. To this end, an example of a simplified flexible data storage card as advertised under the trademark StorCard® is illustrated at 20 in
The housing 22 is sized to be transportable and have a form factor that approximates the size of a credit card. Thus, the housing 22 has a size of approximately 86 mm×54 mm×0.8 mm, although other dimensions are acceptable. With this in mind, the housing is defined by a card top 30 and a base 32. In one embodiment, the card top 30 forms a cover whereas the base 32 forms a bottom. As used throughout the specification, directional terminology such as “cover,” “base,” “upper,” “lower,” “top,” “bottom,” etc., is employed for purposes of illustration only and is in no way limiting.
The card top 30 and the base 32 are sized to be reciprocally mated to one another and are generally rectangular. The card top 30 defines an exterior surface 34 and an interior surface 36. An electronic chip 38 is mounted to the card top 30 exterior surface 34 and controls the flow of data to and from the flexible data storage card 20. In a similar fashion, the base 32 defines an outer surface 40 and an inner surface 42. The card top 30 is generally formed of a thin laminate of plastic and metal layers. The base 32 is generally formed of thin metallic layers secured to each another. As an example, the card top 30 and the base 32 can each be formed from two layers, the layers having a thickness of about 0.003 inch, such that the card top 30 and the base 32 are flexible. After assembly, the flexible data storage card 20 is transportable, for example, in a wallet, and can be flexed in both the transverse and longitudinal directions without damage to the disc 28.
Additionally, an access window 44 is formed in the base 32 to permit access by a read/write head (not shown) to the media side 29 of the flexible media disc 28. In particular, a shutter 46 is provided on the inner surface 42 and has a shutter window 48 that is configured to permit selective access by the read/write head to the media side 29 of disc 28 when at least partially aligned with the access window 44.
During a read/write operation, the shutter 46 is displaced and the read/write head (not shown) enters the housing 22 via the access window 44 and the shutter window 48. The flexible media disc 28 rotates at approximately 3600 rpm a small distance above the read/write head without contacting the read/write head. In this regard, the flexible media disc 28 is said to “fly” above the read/write head. The high rotational rate of the flexible media disc 28 creates an air bearing between the flexible media disc 28 and the read/write head. To ensure accurate and reproducible reading and writing by the read/write head, a media reference surface 50 is provided on the interior surface 36 of the card top 30. The media reference surface 50 is positioned opposite the read/write head and opposite the media side 29 of disc 28. In this way, the spinning flexible media disc 28 is constrained to a reference position between the read/write head and the media reference surface 50.
The first wiping pad 24 and the second wiping pad 26 are of a type known in the art and are generally characterized as soft fibrous sheets that are configured to capture dust and debris generated when the flexible media disc 28 rotates between the wiping pads 24, 26. The wiping pads 24, 26 can be either woven or non-woven fibrous pads that are preferably formed to be non-linting. In addition, the wiping pads 24, 26 are configured so as not to obstruct the interaction between the flexible media disk 28 and the media reference surface 50.
The flexible media disc 28 (hereinafter media disc 28) is of a type known in the art and generally includes a thin sheet of polyester or similar material that is coated with a magnetic slurry on the media side 29. For example, the thin sheet of polyester is approximately 0.003 inch thick and includes a slurry coated layer of magnetic particles. A bottom view of the interior surface 36 of the card top 30 is illustrated in
The media reference surface 50 defines an exposed surface 60 and an attachment surface 62. The attachment surface 62 is in contact with the interior surface 36 of the card top 30 (
The media reference surface 50 is characterized by the desired optically smooth exposed surface 60 and the rounded edge 78 formed at the leading edge 64. The prior art media reference surfaces have been produced one-at-a-time and require various hand polishing steps to achieve the optically smooth surface 60 and rounded leading edge 78. As constrained by the prior art method of manufacture, the prior art media references surfaces are essentially custom crafted parts characterized by low part throughput and high part cost. As a general practice, the prior art media reference surfaces are first formed to a desired shape and then painstakingly polished and sized throughout various handling operations to achieve the smooth exposed surface and the rounded leading edge. Accordingly, the prior art method of manufacturing media reference surfaces is not suited to high volume production of flexible data storage cards. In contrast to the prior art method for making media reference surfaces, a novel process for manufacturing media reference surfaces accurately and inexpensively has been developed. This new method of manufacturing media reference surfaces, described below, enables rapid production of media reference surfaces without hand polishing.
An exemplary method of manufacturing a media reference surface according to one embodiment of the present invention is schematically illustrated at 80 in
In one exemplary embodiment, the process 80 for manufacturing a plurality of media reference surfaces 82 is as follows. A container 100 provides a source of continuous metal sheeting 102 that is fed into a forming apparatus 104. The metal sheeting 102 is selected to have a width that corresponds to a length of the completed media reference surfaces 82. As oriented in
The forming apparatus 104 includes a punch 106 and a die 108. The die 108 positions the metal sheeting 102 such that with each cycle of the punch 106, a single one of the media reference surfaces 82 is produced. After each cycle of the punch 106, the metal sheeting is indexed a distance corresponding to one part width 109, such that the next media reference surface 82 is positioned for formation. The width 109 is selected to provide adequate clearance for the read/write head 72 (
The metal sheeting 102 is configured to provide the optically smooth surface 84 and the attachment surface 94. For example, the metal sheeting 102 can be mechanically treated and/or polished such that at least one side is optically smooth. Specifically, where one side of the metal sheeting 102 is polished to have an average surface roughness Ra not greater than 8 micro-inch, the edges of the metal sheeting 102 will be nearly razor sharp. Accordingly, the metal 102 sheeting provides a highly polished surface but is in itself not suited for use as a media reference surface 82 due to sharp edges. In a preferred embodiment, the metal sheeting 102 is a non-magnetic material (such as stainless steel) and has a thickness of approximately 0.007 inch.
As illustrated in
The gap 110 is selected based upon the desired curvature at the leading edge 86. In particular, the die roll is effectuated as the punch 106 moves vertically in relationship to the die 108 such that the metal sheeting 102 is sheared in a manner that causes the metal sheeting 102 to mechanically yield before the metal sheeting 102 fractures, thus resulting in the formation of the curved edges 86, 88. In this manner, the curved edges 86, 88 are formed by die rolling via the interaction of the punch 106 and the die 108. Accordingly, if the gap 110 is large, then the curved edges 86, 88 acquire a large radius of curvature. Conversely, if the gap 110 is small, the radius of curvature of the curved edges 86, 88 is small. Therefore, it is desired to maintain a gap 110 that results in a radius of curvature on the curved edges 86, 88 in the range of 0.001-0.007 inch. In this regard, the gap 110 spacing is in the range of 0.005 inch to 0.0001 inch, more preferably the gap 110 spacing is between 0.003 inch and 0.0003 inch, even more preferably the gap 110 spacing is between 0.002 inch and 0.0005 inch, and most preferably the gap 110 is approximately 0.001 inch.
With each cycle of the punch 106, a media reference surface 82 is formed having the curved leading edge 86. As the plurality of media reference surfaces 82 are formed, a receptacle 112 is positioned to receive the finished parts. At the completion of one full process cycle of the punch 106, the curved trailing edge 88 is again positioned adjacent the punch 106. In this way, the metal sheeting 102 is indexed into the punch 106 and the die 108 such that the curved leading edge 86 and the curved trailing edge 88 are formed with each cycle of the punch 106. During formation of the curved edges 86, 88, the protective liner 90 is torn at a forward edge 112.
With regard to the process illustrated in
As noted above, with each cycle of the punch 106, a media reference surface 82 is formed having the curved leading edge 86 and the curved trailing edge 88. The receptacle 112 captures the completed media reference surfaces 82 that are suited for use in flexible data storage cards 20 (
In another embodiment of a post process, an added step is employed that deposits an adhesive to the attachment surface 94. In one embodiment, the adhesive is an adhesive tape approximately 0.001 inch thick. In still another embodiment, the adhesive is an ultra violet (UV) cured adhesive applied to the attachment surface 94.
The processing technique associated with
Another embodiment of a method of manufacturing a media reference surface in accordance with the present invention is illustrated in cross-section at 120 in
In a specific example of employing the attachment edges 134 in an assembly operation, it should be noted that as depicted in
In another embodiment, the processed strip 136 of conjoined media reference surfaces 132 is subsequently post processed. In particular, in a preferred embodiment, the processed strip 136 is introduced into electro-polishing equipment, for example, an electro-polishing bath, to polish and refine the curved leading edge 133. In this regard, the media reference surfaces 132 are conjoined by the attachment edges 134 such that each of the curved leading edges 133 is polished a like amount in the electro-polishing bath. After the desired amount of electro-polishing, the processed strip 136 is removed for subsequent separation and assembly of each individual media reference surface 132 to the card top 30 (
Yet another alternate method of processing a metal sheet 150 into a plurality of media reference surfaces in accordance with the present invention is illustrated in
As illustrated in
Although specific embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations calculated to achieve the same purposes may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. Those with skill in the chemical, mechanical, electromechanical, electrical, and computer arts will readily appreciate that the present invention may be implemented in a very wide variety of embodiments. This application is intended to cover any adaptations or variations of the preferred embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.