Patent Application
20050139708
The present invention relates to a tape reel assembly for a data storage tape cartridge. More particularly, it relates to a tape reel assembly having wear resistant driven teeth.
Data storage tape cartridges have been used for decades in the computer, audio, and video fields. The data storage tape cartridge continues to be a popular device for recording large volumes of information for subsequent retrieval and use.
A data storage tape cartridge generally consists of an outer shell or housing maintaining at least one tape reel assembly and a length of magnetic storage tape. The storage tape is wrapped about a hub portion of the tape reel assembly and is driven through a defined path by a tape drive system. The housing normally includes a separate cover and a separate base. Together, the cover and base form an opening (or window) at a forward portion thereof permitting access to the storage tape by a read/write head upon insertion of the data storage tape cartridge into a tape drive. The interaction between the storage tape and head occurs within the housing for a mid-tape load design. Conversely, the interaction between the storage tape and head occurs exterior the housing where the read/write head is annexed for a helical drive design. Where the tape cartridge/drive system is designed to direct the storage tape away from the housing, the data storage tape cartridge normally includes a single tape reel assembly employing a leader block design. Alternately, where the tape cartridge/drive system is designed to provide head/storage tape interaction within the housing, a dual tape reel configuration is typically employed.
Regardless of the number of the tape reel assemblies associated with a particular data storage tape cartridge, the tape reel assembly itself is generally comprised of three elements: an upper flange, a lower flange, and a hub. The hub forms a tape-winding surface about which the storage tape is wound. The flanges are disposed at opposite ends of the hub and spaced apart to accommodate a width of the storage tape. To reduce the likelihood of the storage tape undesirably contacting one of the flanges during a winding operation, the flange-to-flange spacing is selected to be slightly greater than the width of the tape.
Reading information from, or writing information to, the storage tape requires the tape reel assembly to be rotated such that a desired portion of the storage tape can be located and accessed by a read/write head. To this end, the cartridge is inserted into the tape drive with the read/write head. The tape drive rotates the tape reel assembly, thereby driving the tape across the read/write head. To facilitate this operation, tape reel assemblies have driven teeth suited for engagement by a drive chuck of the tape drive. The drive chuck engages the driven teeth of the tape reel assembly (known as “chuck-up”) and rotates (i.e., drives) the tape reel assembly to wind/unwind the data storage tape. Significantly, the drive chuck is typically formed of a hardened material, often metal. Consequently, the drive chuck can cause the driven teeth to wear.
Tape reel assemblies are typically formed from plastic components. Plastic driven teeth, though cost effective, can be ablated by the drive chuck. As the driven teeth wear down, debris is created. The debris from the driven teeth can be spread throughout the tape drive system. In particular, debris spread to the data storage tape can interfere with the reading and writing of information to the data storage tape. In addition, frequent access to the information stored on the data storage tape necessitates frequent tape reel assembly/drive chuck interaction, leading to increased debris generation. Eventually, debris from worn driven teeth can contribute to cartridge loading failures, read/write errors, and other system problems.
Data storage tape cartridges are useful tools for collecting and protecting information stored on data storage tape. However, the driven teeth of the tape reel assembly are vulnerable to wear when repeatedly engaged by the drive chuck of the tape drive system. In particular, plastic driven teeth create debris as they wear. To this end, debris generation during tape reel/tape drive engagement can create errors in reading from, and writing to, the storage tape. Therefore, a need exists for a tape reel assembly having wear resistant driven teeth.
One aspect of the present invention relates to a tape reel assembly for a data storage tape cartridge. The tape reel assembly includes a hub defining a tape-winding surface and driven teeth defining an engagement surface. In this regard, the driven teeth are formed from a polymer including a lubricating additive.
Another aspect of the present invention relates to a data storage tape cartridge. The data storage tape cartridge includes a housing defining an enclosed region, at least one tape reel assembly, and a storage tape. The tape reel assembly is rotatably disposed within the enclosed region and includes a hub defining a tape-winding surface and driven teeth defining an engagement surface. In this regard, the driven teeth are formed from a polymer including a lubricating additive.
Yet another aspect of the present invention relates to a method of fabricating a tape reel assembly for a data storage tape cartridge. The method includes providing a polymer including a lubricating additive. The method additionally includes forming driven teeth defining an engagement surface from the polymer. The method ultimately includes generating a hub to which the driven teeth are connected.
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.
An exemplary single reel data storage tape cartridge according to one embodiment of the present invention is illustrated at 20 in
The housing 22 is sized for insertion into a typical tape drive (not shown). Thus, the housing 22 exhibits a size of approximately 125 mm×110 mm×21 mm, although other dimensions are equally acceptable. With this in mind, the housing 22 is defined by a first housing section 34 and a second housing section 36. In one embodiment, the first housing section 34 forms a cover and the second housing section 36 forms a base. 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 first and second housing sections 34 and 36, respectively, are sized to be reciprocally mated to one another to form an enclosed region 37 and are generally rectangular, except for one corner 38 that is preferably angled and forms a tape access window 40. The tape access window 40 serves as an opening for the storage tape 28 to exit from the housing 22 such that the storage tape 28 can be threaded to a tape drive system (not shown) when the leader block 30 is removed from the tape access window 40. Conversely, when the leader block 30 is stowed in the tape access window 40, the tape access window 40 is covered.
In addition to forming a portion of the tape access window 40, the second housing section 36 also forms a central opening 42. The central opening 42 facilitates access to the tape reel assembly 26 by a drive chuck of the tape drive (not shown). During use, the drive chuck enters the central opening 42 to disengage the brake assembly 24 prior to rotating the tape reel assembly 26 for access to the storage tape 28. The brake assembly 24 is of a type known in the art and generally includes a brake body 44 and a spring 46 co-axially disposed within the tape reel assembly 26. When the data storage tape cartridge 20 is idle, the brake assembly 24 is engaged with a brake interface 48 to selectively “lock” the single tape reel assembly 26 to the housing 22.
The storage tape 28 is preferably a magnetic tape of a type commonly known in the art. For example, the storage tape 28 may consist of a balanced polyethylene naphthalate (PEN) based material coated on one side with a layer of magnetic material dispersed within a suitable binder system and coated on the other side with a conductive material dispersed within a suitable binder system. Acceptable magnetic tape is available, for example, from Imation Corp., of Oakdale, MN.
The leader block 30 covers the tape access window 40 during storage of the cartridge 20 and facilitates retrieval of the storage tape 28 for read/write operations. In general terms, the leader block 30 is shaped to conform to the window 40 of the housing 22 and to cooperate with the tape drive (not shown) by providing a grasping surface for the tape drive to manipulate in delivering the storage tape 28 to the read/write head. In this regard, the leader block 30 can be replaced by other components, such as a dumb-bell shaped pin. Moreover, the leader block 30, or a similar component, can be eliminated entirely, as is the case with dual reel cartridge designs.
The present invention, as more fully described below, is beneficially employed in cartridges with either a single tape reel assembly or a multiple tape reel assembly design. With this in mind, and with reference to
The hub 50 includes a core 70 and defines an interior surface 72 and a tape-winding surface 74. The tape-winding surface 74 is configured for acceptance of the data storage tape 28 (
With additional reference to
The lubricating additive can be any melt processable additive that reduces the abrasion between the driven teeth 56 and the drive chuck (not shown). Suitable lubricating additives include, but are not limited to, silicones, waxes, polytetrafluoroethylene, fluoroploymers, fluorochemicals, and oils. The lubricating additive can be compounded into the polymer, or alternately, the lubricating additive can simply be blended into the polymer. In any regard, the lubricating additive is melt processable and serves to increase the lubricity of the driven teeth 56 and the engagement surface 84.
The lubricating additive is preferably added to the polymer in the range of 0.5 to 25% by weight, more preferably, the lubricating additive is added to the polymer in the range of 2-10% by weight, and most preferably the lubricating additive is added to the polymer at 5% by weight.
In a preferred embodiment, the driven teeth 56 are formed from a polymer including a glass-filled polycarbonate and polytetrafluoroethylene as a lubricating additive added at up to 25% by weight. For example, it has been advantageously discovered and described herein that driven teeth 56 formed from a polymer including 20% glass-filled polycarbonate and 5% polytetrafluoroethylene will resist wear associated with more than 10,000 engagements with the drive chuck (not shown).
After formation of the tape reel assembly 26, the lubricating additive resides in the driven teeth 56 and is present on the engagement surface 84 of the lower flange 54. In one embodiment, the driven teeth 56 are formed from a polymer including glass-filled polycarbonate for stiffness and a lubricating additive for abrasion resistance (i.e., lubricity). In particular, the lubricating additive in the driven teeth 56 and present on the engagement surface 84 permits thousands of couplings of the tape reel assembly 26 to the drive chuck (not shown) without appreciable wear being imparted to the driven teeth 56. The lubricated driven teeth 56 according to the present invention generate much less debris than conventional driven teeth, and contribute to error free loading of the data storage tape cartridge 20 (
The data storage tape cartridge 20 including the tape reel assembly 26 is shown in a final, assembled form in
As a point of reference, the data storage tape cartridge 20 is shown in
Reading or writing information to the storage tape 28 (
After the cartridge 20 is engaged in the tape drive 102, the drive chuck 106, when rotated by the motor 104, rotates the tape reel assembly 26. During some read/write operations, the tape reel assembly 26 can be rotated at speeds on the order of 2000 RPM or more to achieve data storage tape 28 (
Cartridge loading failures are characterized by a rejection of the data storage tape cartridge by the tape drive, thus interfering with the reading and writing of data to the data storage tape. In accordance with the present invention, an improved tape reel assembly is disclosed having wear resistant driven teeth that enable more than 10,000 insertions of the cartridge 20 into the tape drive 102 without a loading failure. In particular, during use, the tape reel assembly 26 maintains a length of the storage tape 28 (
An alternative embodiment of a tape reel assembly 120 in accordance with the present invention is illustrated in
A cross-sectional view of the hub portion 122 in accordance with the present invention is illustrated in
As described above, the wrapping of successive layers of the storage tape 28 (
The following examples further describe the tape reel assemblies of the present invention, methods of forming the tape reel assemblies, and the tests performed to determine their various characteristics. The examples are provided for exemplary purposes to facilitate an understanding of the invention, and should not be construed to limit the invention to the examples.
Tape reel assemblies were constructed as described below, and assembled into a set of data storage tape cartridges. Each of the cartridges were then repeatedly loaded into a series of side-loading tape drives from Seagate Removable Storage Solutions, now Certance of Costa Mesa, Calif. During loading, a drive chuck of the tape drive engaged, rotated, and disengaged a respective one of the tape reel assemblies. The series of steps including loading of the cartridge into the tape drive, the drive chuck engaging, rotating, and disengaging with the tape reel assembly, and unloading of the cartridge is designated as a “cycle.” A successful cycle is defined to be the completion of each of the steps listed above. An unsuccessful cycle is a cycle having a cartridge loading failure, or a cycle wherein a cartridge is rejected by the tape drive. When a cartridge tallies 10,000 successful cycles, the cartridge is said to “pass” the challenge. A “pass rate” represents the number of cartridges that pass the challenge in relation to the number of cartridges that were subjected to the challenge. For each Example and Comparative Example, the number of successful cycles was recorded, with the pass rate appearing in Table 1.
Tape reel assemblies according to
Tape reel assemblies according to
Tape reel assemblies according to
Tape reel assemblies according to
Tape reel assemblies according to
As represented in Table 1 below, the inventive tape reel assemblies (described above), having driven teeth formed from a polymer including PTFE as a lubricating additive, each exceeded the 10,000 cycle cartridge loading challenge with zero cartridge loading failures.
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 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 appreciate that the present invention can be implemented in a wide variety of embodiments. Specifically, a number of other tape reel assembly constructions other than those shown are within the scope of this invention. In particular, this application is intended to cover any adaptations or variations of tape reel assemblies having driven teeth formed from a polymer including a lubricating additive. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
