Tape cartridge

A single reel tape cartridge capable of achieving high-speed read/write access to tapes at high density by enhancing the molding accuracy of lower flange and eliminating inclination and waviness of flange walls is provided. A reel incorporated in a main case is composed of an upper flange, a lower flange, and a boss which is integrally plastic-molded with the lower flange for taking up a magnetic tape. An exit port for allowing an operating nail of an unlock tool to get in and out is open on the bottom wall of the boss. The lower flange is molded in the state that a bridging piece extending along radial direction of the lower flange is formed in the exit port, so that resin flow to the flange wall radially outside the exit port is promoted. The bridging piece is removed after the lower flange is molded.

BACKGROUND OF THE INVENTION

The present invention relates to a single reel tape cartridge in which only one reel for winding magnetic tapes is housed inside a main case.

This type of tape cartridge has a reel lock mechanism between a reel and a main case so as to prevent the reel from idly rotating during unused time. The reel lock mechanism is available in several configurations. One configuration is such that the entire reel is pressed toward a lower case by a circular-plate-shaped reel presser so that lock teeth provided between the reel presser and a lower flange are engaged with each other to prevent idle rotation of the reel (see, e.g., JP 2003-187548 A, paragraph 0016, FIG. 3). The reel presser is supported in such a way as to allow vertical movement but not to allow rotation, and is constantly depressed downward by means of a lock spring. In this example, a gin unlock tool is disposed on the inner face of a bottom wall of a boss of the lower flange, and by operating the unlock tool so as to be pushed upward by a drive shaft of a tape drive, locked engagement between the reel presser and the lower flange is cancelled and the reel is rotatably driven.

The unlock tool is formed from a component extending three arms radially to the outer circumference from a principal surface wall in the center and having downward operating nails at the top ends of the respective arms. In order to protrude each operating nail to the lower face of the case, three exit ports are provided on the bottom wall of the boss in a vertically penetrating way. Drive teeth engaging with the drive shaft are intermittently formed on the outer face of the bottom wall of the boss, and the exit ports are provided in between the teeth.

In order to enhance the molding accuracy of flange walls, the present invention aims at optimizing a flow route of resins when lower flanges are molded. Enhancing the molding accuracy by partially changing the structure of the lower flanges are known to public as disclosed in JP 2004-87067 A (paragraph 0049, FIG. 9) for example. In this example, the structure of a position reference plane formed at three locations on the lower face of a bottom wall of a boss is changed. More specifically, the position reference plane originally having a solid structure is changed into a C-shaped frame so as to prevent “surface sink” during molding. It is to be noted that a reel lock mechanism in this example prevents idle rotation of the reel during unused time by engaging lock teeth formed on the periphery of a lower flange with a reel lock. Consequently, the exit ports for operating nails essential for the former example are not formed on the bottom wall of the boss in this example.

When the exit ports are formed on the bottom wall of the boss across the circumferential direction as described before, melted resin flows while de-touring the exit ports during molding process of the lower flange. Consequently, when the melted resin which detoured the exit ports converge, weld lines are generated, which causes uneven filling of resin and creates distortion on flange walls. More specifically, when a gate position is set in the center on the lower face of the low flange, a resin flow to a flange wall on an extension of an exit port tends to delay in proportion to the resin flow to other sections. This causes dispersion in filing density of resin on the flange wall in circumferential direction, generating waviness and inclination on the flange wall after solidification. The run-out amount on the flange face caused by the waviness and the inclination amounts to maximum 0.292 mm, which has been a major hurdle of achieving high-density and high-speed read/write access to magnetic tapes.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a single reel tape cartridge capable of achieving high-speed read/write access to magnetic tapes at high density by optimizing a flow pattern of resin during molding of lower flanges so as to enhance the molding accuracy of flange walls for ensuring an appropriate winding posture of magnetic tapes wound onto the reel and solving problems such as damages on tape edges.

A tape cartridge in the present invention has a single reel2disposed inside a main case1for taking up a magnetic tape3as shown inFIG. 2. The reel2is a plastic molding formed by integrally molding a lower flange11and a boss12for taking up the magnetic tape3. A reel lock mechanism is formed between a bottom wall of the boss12and an upper case1aof the main case1for keeping the reel2in a locked state so as not to rotate when not in use. As shown inFIG. 3, an unlock tool25is disposed on an inner face of the bottom wall of the boss12for unlock operation of the reel lock mechanism. An exit port18is formed on the bottom wall of the boss in a region close to an outer circumference so as to connect inside and outside. The unlock tool25has an operating nail28facing a lower face of the case from the exit port18.

The unlock tool25may be a component extending three arms27at regular intervals in circumferential direction to the outer circumference from a principal surface wall26in the center and having operating nails28formed downward in extended ends of respective arms27in order to secure stability offered by three-point support as shown inFIG. 2. In this case, three exit ports18corresponding to the respective operating nails28are formed on the boss12. If the circumferential length of respective exit ports18is sufficiently secured, the operating nails28may be moved in and out with their circumferential length being made large enough to allow for mechanical strength of the operating nails28themselves. However, the larger the circumferential length of the respective exit ports18becomes, the more the flowability of the resin during molding of the lower flange11is disturbed. This should be taken into consideration in the present invention.

According to the present invention, in the single reel tape cartridge, as shown inFIG. 1, the boss12is molded integrally with a bridging piece31which seals at least a part of the exit port18, and during molding of the lower flange11and the boss12, a melted molding resin is made to flow between the boss12and the lower flange11through the bridging piece31in radial direction at a region where the exit port is present.

More specifically, as shown inFIG. 1, a gate position G for resin injection during molding of the lower flange11and the boss12is set in the center of a lower face of the bottom wall of the boss12. According to this structure, a melted resin injected into the gate position G during molding of the lower flange11flows from the side of the boss12to the side of the lower flange11through the bridging piece31in the exit port18.

The bridging piece31is removed after the lower flange11is molded so that the exit ports18can be fully opened. In this case, in order to facilitate removal of the bridging piece31, the bridging piece31may be linked to the inner circumferential face of an opening of the exit ports18through a thinned critical sectional portion32.

A plurality of bridging pieces31may be dispersed in circumferential direction in one exit ports18as shown in a second embodiment inFIG. 7andFIG. 8. It is preferable, however, to dispose one bridging piece31in the circumferential center of one exit ports18. In this case, the bridging piece31may be formed on a phantom line P connecting the gate position G and the circumferential central portion of the exit port18.

Moreover, in the present invention, as shown inFIG. 11andFIG. 12, one bridging piece31may be integrally formed in a circumferential central region of one exit port18in such a way that both radial ends of the bridge piece are connected to an inner circumferential face of the exit port18so as to remain. The term “remain” herein indicates that the bridging piece31is not removed but used. In the operating nail28in this case, an undercut for avoiding contact interference with the bridging piece31may be formed so that the operating nail28can get in and out of gaps36formed on both circumferential sides of the exit port18which interpose the bridging piece31.

In the present invention, during molding of the lower flange11, melted molding resin flows in radial direction through the bridging piece31in a region where the exit port18is present. In this case, with a gate position G for resin injection being set in the center of the lower face of the bottom wall of the boss12, the melted resin injected into the gate position G flows from a molded space of the boss12to a molded space of the lower flange11. Therefore, in the lower flange11, the filing density on the flange wall in circumferential direction becomes uniform, which enhances the molding accuracy. As a result, waviness and inclination on the lower flange wall11of the reel2after molding are eliminated, so that considerable reduction in run-out amount on the flange face is achieved, the winding posture of the tape3wound onto the reel2becomes more appropriate than that in the case of conventional reels, and damages on tape edges and the like are cleared away, thereby making it possible to achieve high-speed read/write access of signals to the tape3at high density. Since the flow pattern of the resin can be optimized without drastic change in mold, there is also an advantage that the lower flange11with the boss12can be integrally molded at low costs with use of existing injection molds.

With the bridging piece31being removed after molding of the lower flange11, the exit port18is made to be fully open as desired as in the case with forming the exit port18to have enough circumferential length by casting with use of a mold. Therefore, since it is not necessary to change the shape and the structure of the operating nail28of the unlock tool25which can get in and out of exit port18, an existing unlock tool25may be applied without modification, which allows the costs necessary for manufacturing tape cartridges to be reduced proportionally. More particularly, it becomes possible to form the operating nail28to be long and wide in circumferential direction for securing the strength.

With both the radial ends of the bridging piece31being linked to the inner circumferential face of the exit ports18through the critical sectional portion32, the bridging piece31can easily be removed with use of the critical sectional portion32. Therefore, the bridging piece31can be removed without troubles.

When the gate position G is set in the center of the lower face of the bottom wall of the boss12, and one bridging piece31is formed on a phantom line P connecting the gate position G and the circumferential central portion of the exit port18, melted resin injected from the gate G position flows by the most direct way to a flange wall portion radially outside the exit port18through the molded space of the bridging piece31, which makes the filing density of the flange wall in circumferential direction more uniform and makes it possible to secure high molding accuracy of the flange wall.

Leaving the bridging piece31in the exit port18, forming the undercut35on the operating nail28for avoiding contact interference with the bridging piece31, and allowing the operating nail28to get in and out of the exit port18through the gap36between the bridging piece31and the inner circumferential face of the exit port18bring about an advantage that the exit port18can be reinforced by the bridging piece31while labor of removing the bridging piece31is saved to reduce the processing costs of the lower flange11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIGS. 1-6show a single reel tape cartridge of a first embodiment in the present invention. InFIG. 2, the tape cartridge has a box-type main case1and a single reel2housed therein, and a magnetic tape (hereinbelow simply referred to as a tape)3for recording magnetic signals is wound onto the reel2.

A loading pin4used for pulling the tape3out of the case1is connected to a leading end of the tape3. In the state that the loading pin4faces a tape pullout port5on the front right corner of the main case1, the upper and lower ends of the loading pin4are held by and fixed onto a holder formed on the main case1. The tape pullout port5can be opened and closed with a slidable lid6. The lid6is movably biased so as to be freely closed by an unshown spring. The main case1is structured such that an upper case1aand a lower case1brespectively made of plastic are combined in a lid coupling state. A drive port7for driving the reel2is provided on the bottom wall of the lower case1b.

The reel2is a plastic molding including an upper flange10, a lower flange11, and a boss12integrally formed with the lower flange11. The boss12is formed into a cylindrical shape having a bottom face and an opened upper face, and a starting end of the upper flange10is welded afterward to the upper opening circumference of a cylindrical circumferential wall of the boss12. The tape3is wound around the outer circumferential face of the cylindrical circumferential wall of the boss12.

InFIG. 1andFIG. 3, on the lower face of a round bottom wall of the boss12, drive teeth14engaging with a drive shaft D of a tape drive is integrally formed like a ring in an outer circumferential region around the center, and a adsorption plate16to be adsorbed by a magnet15in the drive shaft D is inserted inside the drive teeth14and secured therein.

The drive teeth14are gear teeth with a saw-teeth cross-section along the radial direction formed at regular intervals in circumferential direction, and has toothless portions17without the drive teeth14at three locations in the circumferential direction.

A reel lock mechanism is provided between the bottom wall of the boss12and the upper case1afor keeping the reel2not in use in locked state so as not to rotate. InFIG. 3, the reel lock mechanism is composed of a reel presser19, a helical compression spring20for depressing downward the reel presser19, annular lock teeth21formed on the lower face of the bottom wall of the reel presser19, and annular lock teeth22formed on the upper face of the bottom wall of the boss12for engaging with the lock teeth21.

The reel presser19is formed in a circular plate shape with an opened upper face, and has four L-shaped ribs protruding upward in the center of the inner face. A cross-shaped guide protrusion24formed on the inner face of the upper case1ais guided into a cross-shaped slide groove23enclosed by these ribs, by which the reel presser19is supported slidably in vertical direction but not rotatably around a vertical center of axle. A semicircle socket is formed in the center of the lower face of the reel presser19, and a ball (steel ball)29for minimizing friction resistance with the unlock tool25is embedded in the socket so as to be rotated freely in the state of being exposed to the lower side.

When the tape cartridge is not used, the lock teeth21,22engage with each other as shown inFIG. 3to prevent the reel2from rotating. When the tape cartridge is loaded into the tape drive and the reel presser19is operated to press up against the spring20, the engagement between both the lock teeth21,22is cancelled to put the reel2in a free rotation state.

In order to perform unlocking operation of the reel presser19on the tape drive side, an unlock tool25is disposed between the reel presser19and the bottom wall of the boss12. Three circumferential locations in the lock teeth22formed on the upper face of the bottom wall of the boss12are notched so as to dispose arms27of the unlock tool25.

The unlock tool25is made of a stainless press metal fitting extending three arms27at regular intervals in circumferential direction to an outer circumference from a principal surface wall in the center and having operating nails28formed in the state of being folded downward in extended ends of the respective arms27. If necessary, a part or the entire unlock tool25may be formed from plastic molding materials.

As shown inFIG. 3, a principal surface wall26of the unlock tool25receives the reel presser19through the ball23. Consequently, when the reel lock mechanism is in a locked state, the principal surface wall26and the arms27are pressed toward the bottom wall of the boss12, and the respective operating nails28protrude downward from the exit ports18. As shown inFIG. 4, operating the operating nails28to be pushed up by the drive shaft D allows unlocking operation of the reel lock mechanism.

The aim of the present invention is to have an appropriate flow pattern of resin during molding of the lower flange11so as to enhance the molding accuracy of the flange wall portion of the lower flange11in the thus-structured tape cartridge. More particularly, the lower flange11is injection-molded by injecting melted resin from the gate position G (seeFIG. 5) set in the center of the lower face of the bottom wall of the boss12. In this case, the molding is performed with a bridging piece31being formed on the exit port18, which promotes resin flowability to the flange wall portion radially outside the exit port18, and uniforms the filing density of the flange wall in circumferential direction.

In order to straighten the flow line of the melted resin and to shorten its flow route length, one bridging piece31was disposed in a central circumferential portion in every exit port18, and both radial ends of the bridging piece31were integrally connected to the inner circumferential wall of an opening of the exit port18. More particularly, the bridging piece31was formed on a phantom line P connecting the center of the gate position G, i.e., the center of the lower face of the bottom wall of the boss12, and the circumferential center of the exit port18as shown inFIG. 1.

InFIG. 5andFIG. 6, the vertical thickness size of the bridging piece31was set to be almost identical to the thickness of the bottom wall of the boss12. The circumferential length of the bridging piece31was naturally set to be smaller than that of the exit port18.

More specifically, both the radial ends of the bridging piece31were linked to the inner circumferential face of the exit port18through a critical sectional portion32thinner than the bridging piece31. The bridging piece31including the critical sectional portion32is cut away by utilizing the critical sectional portion32after the lower flange11is molded, so that the exit port18can be formed to have a desired opening area.

Thus, according to the lower flange11molded with the presence of the bridging piece31, it became possible to uniform the filling density of the resin in the flange wall portion radially outside the exit port18and in other flange wall portions and to solve the problem of waviness and inclination generated on the flange wall after solidification. The run-out amount on the flange face could be reduced to 0.082 mm, which was 72% reduction from the run-out amount of the conventional lower flange. Thus, it became possible to provide a tape cartridge allowing high-density read/write access to the tape3at high speed.

Second Embodiment

FIG. 7andFIG. 8show a bridging piece31in a second embodiment in the present invention. In this case, in the single reel tape cartridge in the first embodiment, two bridging pieces31are disposed in every exit port18in a separated state in circumferential direction, so that during molding of the lower flange11, the flowability of melted resin in the exit port18can be promoted. InFIG. 7, each bridging piece31was formed into a cross-sectional square shape, and was disposed across the exit port18in radial direction so that the bridging piece31was positioned in a central portion in vertical thickness direction of the bottom wall of the boss12as shown inFIG. 8. In this case, the critical sectional portion32was omitted as it was not necessary. Since other structures are identical to those in the first embodiment, like component members are designated by like reference numerals and description thereof is omitted. This applies to following embodiments.

Third Embodiment

FIG. 9andFIG. 10show a bridging piece31in a third embodiment in the present invention. The bridging piece31was made to seal the entire exit port18so as to promote the flowability of melted resin during molding of the lower flange11. The critical sectional portion32was formed along and around the inner circumferential face of the exit port18on both upper and lower faces of the bridging piece31. The vertical thickness size of the bridging piece31in the third embodiment was set to be slightly smaller than the thickness of the bottom wall of the boss12as shown inFIG. 10. This is to facilitate cutting removal of the bridging piece31.

Fourth Embodiment

FIG. 11andFIG. 12show a bridging piece31in a fourth embodiment in the present invention. This embodiment is different from the previous embodiments in the point that each exit port18is formed into an almost square shape long in circumferential direction, a bridging piece31with an oval cross section is integrally formed in the circumferential center of each exit port18in such a way that radial both ends of the bridging piece31are linked to the inner circumferential face of the opening of the exit port18, and the lower flange11is used without removing the bridging piece31. Accordingly, the operating nail28of the unlock tool25is formed in a yoked state having an undercut35for avoiding contact interference with the bridging piece31, and the operating nail28is made to be able to get in and out of the exit port18through two gaps36generated between the bridging piece31and the circumferential opening face of the exit port18.

Although in those embodiments, the bridging piece31was formed in the inner space of the exit port18, the bridging piece31may be formed, if necessary, to have a part protruding from the exit port18, and further the bridging piece31may be formed over the inner face or the outer face of the opening of the exit port18. The gate position G may be set in a plurality of locations closer to the radial center than the exit port18.