(12) United States Patent
`(10) Patent N0.:
`US 6,462,905 B1
`
`Takahashi et al.
`(45) Date of Patent:
`Oct. 8, 2002
`
`US006462905B1
`
`(54) MAGNETIC TAPE CARTRIDGE
`
`(75)
`
`Inventors: Daisuke Takahashi; Hideaki Shiga;
`Seiji Tsuyuki, all of Kanagawa-ken (JP)
`
`EP
`EP
`
`EP
`W0
`WO
`
`0 926 676 A1
`1 054 403 A1
`
`1 058 259 A2
`97/15925
`99/65032
`
`6/1999
`11/2000
`
`12/2000
`5/1997
`12/1999
`
`(73) Assignee: Fuji Photo Film 0)., Ltd.,
`Kanagawa-Ken (JP)
`
`* cited by examiner
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U-S-C- 154(1)) by 132 days,
`
`Primary Examiner—Robert S. Tupper
`(74) Attorney, Agent, or Firm—Sughrue Mion, PLLC
`
`(21) Appl. N0.: 09/707,774
`
`(57)
`
`ABSTRACT
`
`(22)
`
`Filed:
`
`Nov. 8, 2000
`_
`_
`_
`.
`_
`Forelgn Applicatlon Prlorlty Data
`(30)
`Nov. 8, 1999
`(JP)
`........................................... 11—317166
`Nov. 9, 1999
`(JP)
`........................................... 11—318464
`(51)
`Int. C1.7 .............................................. GllB 23/027
`52
`U S Cl
`360/132
`(
`)
`_'
`'
`' """"""""""""""""""""""""""""0
`I
`(58) Fleld of Search ....................... 360/132, 242/338.1,
`242/3382
`
`(56)
`
`.
`References Clted
`Us. PATENT DOCUMENTS
`
`2:33:63: 2
`121333 kin/:3?“ fit “‘1 """" 24224333814;
`6,113,020 A ,5 92000 Nae aklsm et a ‘ """"242/3/38 1
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`6:234:416 B1 *
`5/2001 Na§ak
`242/3381
`
`6,318,657 B1 * 11/2001 Nayak ...........
`242/3381
`2/2002 Stabfle et a1.
`............... 242/336
`6,344,944 132 *
`FOREIGN PATENT DOCUMENTS
`
`A magnetic tape cartridge includes a magnetic tape wound
`around a single reel, a cartridge casing in which the reel is
`housed for rotation and a reel stopper which locks the reel
`not to rotate when the magnetic tape cartridge is not being
`used and releases the reel
`to permit to rotate when the
`magnet“: tape ‘Farmdge 15 to be “.Sed' The reel “Opp“
`1nc1udes a braklng member wh1ch IS movable between a
`locking position where it is in contact with the reel to restrict
`rotation of the reel and a releasing position Where it is away
`from the reel
`to permit rotation of the same, an urging
`member which urges the braking member toward the lock-
`ing position, and a releasing member which is rotated
`integrally with the reel and moves the braking member
`toward the releasing position in response to a reel chucking
`action of the reel drive means of a tape drive. The braking
`member is provided with a braking gear which is adapted to
`be engaged, to restrict rotation of the reel, with an engage—
`mem g6?“ IOOIh on film engégememprofiqlm formed on Fhe
`reel while the reel IS prov1ded wnh a gulde member wh1ch
`centers the braking member with respect to the reel.
`
`EP
`
`0 284 687 A2
`
`10/1988
`
`4 Claims, 4 Drawing Sheets
`
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`SONY V. FUJI
`
`

`

`US. Patent
`
`Oct. 8, 2002
`
`Sheet 1 0f 4
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`US 6,462,905 B1
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`US. Patent
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`Oct. 8, 2002
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`US 6,462,905 B1
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`US. Patent
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`Oct. 8, 2002
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`Sheet 3 0f4
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`US 6,462,905 B1
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`US. Patent
`
`Oct. 8, 2002
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`Sheet 4 0f4
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`US 6,462,905 B1
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`PRIOR ART
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`I'll,
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`

`

`US 6,462,905 Bl
`
`1
`MAGNETIC TAPE CARTRIDGE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to a magnetic tape cartridge com-
`prising a cartridge casing and a single reel which is housed
`in thc cartridgc casing for rotation and around which a
`magnetic tape is wound, and more particularly to a structure
`of a reel stopper means for preventing rotation of the reel
`when the magnetic tape cartridge is not being used.
`2. Description of the Related Art
`As a recording medium for use in an external memory of
`a computer or the like, there has been known a magnetic tape
`cartridge comprising a magnetic tape wound around a single
`reel and a cartridge casing in which the reel is housed for
`rotation. Since the magnetic tape is used for storing data in
`a computer or the like and important information is stored on
`the magnetic tape, the magnetic tape cartridge is provided
`with a reel stopper means which prevents rotation of the reel
`when the magnetic tape cartridge is not being used, e.g.,
`when the magnetic tape cartridge is being stored, so that
`trouble such as tape jam does not occur and the magnetic
`tape is not accidentally drawn out.
`The reel stopper means is provided with a brake member
`which is adapted to be engaged with the reel to prevent
`rotation of the reel and is disengaged from the reel to permit
`rotation of the reel in response to a reel chucking action of
`the reel drive means of a tape drive such as an external
`memory when the magnetic tape cartridge is loaded in the
`tape drive.
`In order to improve reliability of the action of the reel
`stoppcr means and to prcvcnt dust from cntcring thc car-
`tridge casing, the reel stopper means may be, for instance, of
`a structure comprising a brake member which restricts
`rotation of the reel, an urging member which urges the brake
`member toward a locking position in which the brake
`member restricts rotation of the reel, and a release member
`which is moved in response to a reel chucking action of the
`reel drive means of a tape drive to move the brake member
`toward a release position in which the brake member
`releases the reel to permit rotation of the same.
`That is, when the magnetic tape cartridge is not being
`used, the brake member locks the reel so that the reel is not
`accidcntally rotatcd and thc magnctic tape is not accidcntally
`drawn out, and when the magnetic tape cartridge is loaded
`in a tape drive, the release member drives the brake member
`to release the reel in response to a reel chucking action of the
`reel drive means of the tape drive. In this state, the reel can
`be rotated and loading/unloading of the magnetic tape is
`permitted.
`In such a structure, it is advantageous in simplifying the
`structure that the release member is adapted to be brought
`into abutment against a part of the reel drive means of the
`tape drive and the reel drive means pushes a part of the
`release member to drive the brake member to release the reel
`whcn thc rccl drivc mcans chucks thc rccl. However, in this
`case, when the release member drives the brake member to
`release the reel, the brake member can be inclined as shown
`in FIG. 5 and the gear teeth on the brake member can be
`brought into contact with the rear teeth on the reel while the
`reel is rotated, which results in generation of noise, obstruc-
`tion of rotation of the reel and unstable magnetic tape
`loading/unloading action.
`As a cause of the brake member being inclined, that the
`brake member becomes off-centered and comes to be
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`inclined when the brake member is moved to the locking
`position where the braking gear thereon is brought into
`engagement with an engagement gear on the reel and the
`brake member is moved to the release position in this state
`can be conceived. Further,
`that
`the brake member was
`incorporated in the magnetic tape cartridge inclined relative
`to thc rccl whcn thc magnctic tapc cartridgc was asscmblcd
`can be conceived.
`
`When the braking gear teeth on the brake member are like
`sawteeth in shape and the surface of each tooth facing
`against the tape-unwinding direction of the reel is substan-
`tially normal,
`though rotation of the reel
`in the tape—
`unwinding direction can be surely prevented, there is fear
`that the magnetic tape is cut when the reel is rotated in the
`tape-winding direction due to drop impact when the mag-
`netic tape cartridge drops.
`That is, when the braking gear and the engagement gear
`are engaged with each other at a substantially normal surface
`facing against the tape-unwinding direction, the reel cannot
`be rotated in the tape-unwinding direction. Further, a leader
`mcmbcr such as a lcadcr pin is fixcd to the end of thc
`magnetic tape wound around the reel, and the leader member
`is held near the tape draw-out opening of the cartridge casing
`when the magnetic tape cartridge is not being used. When
`the brake member is moved and the braking gear is disen-
`gaged from the engagement gear due to drop impact with the
`reel rotated in the tape—winding direction under inertia, a
`tape winding force acts on the magnetic tape whose end is
`fixed by the leader member. Since the reel cannot be rotated
`in the tape-unwinding direction or the direction in which the
`tension on the magnetic is released, the tape winding force
`acting on the magnetic tape can stretch the tape to deteriorate
`the magnetic recording and reproducing characteristics,
`remove the leader member from the magnetic tape, cut the
`magnetic tape, or displace the leader member from the
`predetermined position to disable the regular tape draw-out
`action, thereby deteriorating the reliability of the magnetic
`tape cartridge.
`
`SUMMARY OF THE INVENTION
`
`In view of the foregoing observations and description, the
`primary object of the present invention is to provide a
`magnetic tape cartridge in which the braking gear of the reel
`stopper means is suppressed from being brought into contact
`with thc rccl whcn thc rccl stoppcr mcans is in thc rclcasc
`position.
`Another object of the present invention is to provide a
`magnetic tape cartridge in which the reel can be surely
`prevented from being rotated while occurrence of the mag-
`netic tape being cut can be prevented when the magnetic
`tape cartridge is not being used.
`In accordance with a first aspect of the present invention,
`there is provided a magnetic tape cartridge comprising a
`magnetic tape wound around a single reel, a cartridge casing
`in which the reel is housed for rotation and a reel stopper
`means which locks the reel not to rotate when the magnetic
`tape cartridge is not being used and releases the reel to
`permit rotation thereof when the magnetic tape cartridge is
`to be used, wherein the improvement comprises that the reel
`stopper means comprises a braking member which is mov-
`able between a locking position where it is in contact with
`the reel to restrict rotation of the reel and a releasing position
`where it is away from the reel to permit rotation of the same,
`an urging member which urges the braking member toward
`the locking position, and a releasing member which is
`rotated integrally with the reel and moves the braking
`
`

`

`US 6,462,905 B]
`
`3
`member toward the releasing position in response to a reel
`chucking action of the reel drive means of a tape drive, and
`the braking member is provided with a braking gear which
`is adapted to be engaged, to restrict rotation of the reel, with
`an engagement gear tooth on an engagement projection
`formed on the reel while the reel is provided with a guide
`member which centers the braking member with respect to
`the reel.
`
`It is preferred that the guide member comprises guide ribs
`which are formed on the inner surface of the reel hub at at
`
`10
`
`least three places, each having an inclined surface which
`inclines downward from the upper portion of the inner
`surface of the reel hub toward the center of the reel.
`
`In the magnetic tape cartridge in accordance with the first
`aspect of the present invention, when the braking member is
`moved downward from the releasing position to the locking
`position,
`the braking member is centered by the guide
`members so that the braking gear is brought into mesh with
`the engagement gear teeth with the braking member held
`horizontal, whereby the braking member is prevented from
`being inclined in the locking position. When the braking
`member is subsequently moved to the releasing position by
`the releasing member, the braking member is held horizontal
`up to the releasing position. Accordingly, the phenomenon
`that the braking member is inclined can be suppressed,
`whereby the braking gear is prevented from contacting the
`engagement gear teeth to generate noise or to obstruct
`rotation of the reel.
`
`Further, during assembly of the magnetic tape cartridge,
`the braking member is automatically centered in the reel hub
`by the guide members and is incorporated in place in the
`reel, whereby assembly of the magnetic tape cartridge is
`facilitated.
`
`In accordance with a second aspect of the present
`invention, there is provided a magnetic tape cartridge com-
`prising a magnetic tape wound around a single reel, a
`cartridge casing in which the reel is housed for rotation and
`a reel stopper means which locks the reel not to rotate when
`the magnetic tape cartridge is not being used and releases the
`reel
`to permit rotation thereof when the magnetic tape
`cartridge is to be used, wherein the improvement comprises
`that the reel stopper means comprises a braking member
`which is movable between a locking position where it is in
`contact with the reel to restrict rotation of the reel and a
`
`releasing position where it is away from the reel to permit
`rotation of the same, an urging member which urges the
`braking member toward the locking position, and a releasing
`member which is rotated integrally with the reel and moves
`the braking member toward the releasing position in
`response to a reel chucking action of the reel drive means of
`a tape drive, and the braking member is provided with a
`braking gear which is adapted to be engaged,
`to restrict
`rotation of the reel, with an engagement gear on an engage-
`ment projection formed on the reel, the outer diameter of the
`engagement gear being larger than that of the braking gear.
`In the magnetic tape cartridge in accordance with the
`second aspect of the present invention, when the braking
`member is moved downward from the releasing position to
`the locking position, the braking member is centered by the
`dillerence between the outer diameters of the engagement
`gear and the braking gear so that the braking gear is brought
`into mesh with the engagement gear teeth with the braking
`member held horizontal, whereby the braking member is
`prevented from being inclined in the locking position. When
`the braking member is subsequently moved to the releasing
`position by the releasing member, the braking member is
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`held horizontal up to the releasing position. Accordingly, the
`phenomenon that the braking member is inclined can be
`suppressed, whereby the braking gear is prevented from
`contacting the engagement gear teeth to generate noise or to
`obstruct rotation of the reel.
`
`In accordance with a third aspect of the present invention,
`there is provided a magnetic tape cartridge comprising a
`magnetic tape wound around a single reel, a cartridge casing
`in which the reel is housed for rotation and a reel stopper
`means which locks the reel not to rotate when the magnetic
`tape cartridge is not being used and releases the reel to
`permit rotation thereof when the magnetic tape cartridge is
`to be used, wherein the improvement comprises that the reel
`stopper means comprises a braking member which is mov-
`able between a locking position where it is in contact with
`the reel to restrict rotation of the reel and a releasing position
`where it is away from the reel to permit rotation of the same,
`an urging member which urges the braking member toward
`the locking position, and a releasing member which is
`rotated integrally with the reel and moves the braking
`member toward the releasing position in response to a reel
`chucking action of the reel drive means of a tape drive, the
`braking member is provided with a braking gear which is
`adapted to be engaged, to restrict rotation of the reel, with an
`engagement gear tooth on an engagement projection formed
`on the reel, and each of the gear teeth of the braking gear has
`a first
`inclined surface which is brought
`into abutment
`against the engagement gear teeth when the reel is rotated in
`the tape-unwinding direction with the braking gear and the
`engagement gear tooth in mesh with each other and a second
`inclined surface which is brought into abutment against the
`engagement gear teeth when the reel
`is rotated in the
`tape-winding direction with the braking gear and the
`engagement gear tooth in mesh with each other, the first and
`second inclined surfaces forming therebetween an apical
`angle not larger than 90°, and the interior angle between the
`first inclined surface and the vertical being not larger than
`the interior angle between the second inclined surface and
`the vertical.
`
`In the magnetic tape cartridge in accordance with the third
`aspect of the present invention, since the apical angle of the
`braking gear tooth is not larger than 90° and the interior
`angle for the first inclined surface of the braking gear tooth
`which is brought into abutment against the engagement gear
`teeth when the reel is rotated in the unwinding direction and
`the interior angle for the second inclined surface which is
`brought into abutment against the engagement gear teeth
`when the reel is rotated in the winding direction are not
`smaller than 30° with the former smaller than the latter,
`rotation of the reel can be surely prevented and when the reel
`is rotated in the winding direction due to drop impact or the
`like and an excessive winding force acts on the magnetic
`tape, the braking member is moved toward the releasing
`position along the first inclined surface and the braking gear
`is disengaged from the engagement gear teeth, whereby the
`reel
`is rotated in the unwinding direction to reduce the
`tension on the magnetic tape, and the magnetic tape can be
`prevented from being stretched or cut.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective view showing a state of a magnetic
`tape cartridge in accordance with an embodiment of the
`present invention when the magnetic tape cartridge is not
`being used,
`FIG. 2 is a fragmentary cross-sectional View of the
`magnetic tape cartridge shown in FIG. 1 when the magnetic
`tape cartridge is being used,
`
`

`

`US 6,462,905 B]
`
`5
`FIG. 3 is a cross-sectional View taken along line A—A in
`FIG. 2,
`FIG. 4 is a cross—sectional View taken along line B7B in
`FIG. 2, and
`FIG. 5 is a fragmentary cross-sectional View showing a
`state of a magnetic tape cartridge where the braking member
`is inclined.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`A magnetic tape cartridge 1 in accordance with an
`embodiment of the present invention will be described with
`reference to the drawings, hereinbelow.
`The magnetic tape cartridge 1 comprises a cartridge
`casing 3 formed by fastening together upper and lower
`casing halves 31 and 32 by screws or the like. A single reel
`2 around which a magnetic tape (not shown) is wound is
`housed for rotation in the cartridge casing 3. The lower
`casing half 32 is provided with a central opening 32a. The
`magnetic tape cartridge 1 is further provided with a reel
`stopper means 10 which permits rotation of the reel 2 when
`the magnetic tape cartridge 1 is being used and restricts
`rotation of the reel 2 when the magnetic tape cartridge 1 is
`not being used.
`The reel 2 comprises a reel hub 21 which is a cylindrical
`member having a closed bottom and around which the
`magnetic tape is wound, and lower and upper flanges 22 and
`23. The reel hub 21 and the lower flange 22 are integrally
`formed by synthetic resin molding. The upper flange 23 is
`bonded to the reel hub 21, for instance, by ultrasonic
`welding. The reel hub 21 is provided with a bottom wall 21a
`at the lower end portion thereof and a reel gear 24 for
`rotating the reel 2 is annularly formed on the lower surface
`of the bottom wall 21a, and annular reel plate 25 which is
`magnetically attracted by a reel drive means 11 of a record-
`ing and reproducing apparatus is mounted on the lower
`surface of the bottom wall 21a inside the reel gear 24. The
`reel 2 is urged downward by an urging means 5 to be
`described later.
`
`The reel drive means 11 is provided with an annular drive
`gear 13 and a magnet (not shown) disposed on the top
`surface of a rotary shaft 12. When the magnetic tape
`cartridge 1 loaded in a bucket of the tape drive is moved
`downward toward the rotary shaft 12, the drive gear 13 is
`brought into mesh with the reel gear 24 and the reel plate 25
`is magnetically attracted against the magnet to hold the drive
`gear 13 and the reel gear 24 in mesh with each other. In this
`manner, the reel drive means 11 chucks the reel 2.
`The mechanism of the reel stopper means 10 will be
`described, hereinbelow. The reel stopper means 10 com-
`prises a braking member 4 which is movable up and down
`between a locking position where it is in contact with the
`reel 2 to restrict rotation of the reel 2 and a releasing position
`where it is away from the reel 2 to permit rotation of the
`same, an urging member 5 which urges the braking member
`4 toward the locking position, and a releasing member 6
`which moves the braking member 4 toward the releasing
`position.
`As shown in FIG. 3, three through holes 26 are formed in
`the bottom wall 21a of the reel 2 at regular angular intervals
`in the circumferential direction to extend through the portion
`at which the reel gear 24 is formed. On the upper surface of
`the bottom wall 21a, there are erected three pairs of (six)
`engagement projections 27 at regular angular intervals in the
`circumferential direction among the through holes 26. The
`upper end of each engagement projection 27 is formed into
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`an engagement gear teeth 29 as shown in FIG. 4. The
`through holes 26 may be larger than three in number and the
`engagement projections 27 may be larger three pairs in
`number. Further, the upper end of each engagement projec—
`tion 27 may be formed into a single gear tooth.
`The braking member 4 has a disc portion 41 which is
`disposed in the reel hub 21 opposed to the bottom wall 21a,
`and an annular braking gcar 42 is formed on thc lowcr
`surface of the disc portion 41 along the outer peripheral edge
`thereof. The braking gear 42 is adapted to be engaged with
`the engagement gear 29 on the engagement projections 27.
`The central part of the lower surface of the disc portion 41
`is convex downward and forms a sliding portion 41a which
`is pressed against a sliding portion 61a on the upper surface
`of a body portion 61 of a releasing member 6 to be described
`later.
`
`The outer diameter D of the engagement gear formed by
`the engagement gear teeth 29 on the engagement projections
`27 on the reel 2 (FIG. 3) is larger than the outer diameter d
`(FIG. 2) of the braking gear 42 on the braking member 4.
`The braking gear 42 and the engagement gear 29 are conical
`in shape and the height of each tooth is higher at the outer
`periphery thereof. Accordingly,
`the braking gear 42 is
`engaged with the engagement gear 42 at their outer periph-
`eries first.
`
`When the braking gear 42 on the braking member 4 is
`brought into mesh with the engagement gear 29 on the
`engagement projections 27, the outer periphery of the brak-
`ing member 4 is guided by guide members 39 formed on the
`inner surface of the reel hub 21 of the reel 2. The guide
`members 39 are respectively provided between each pair of
`engagement projections 27, and accordingly three guide
`members 39 are provided on the inner surface of the reel hub
`21. Each guide member 39 is in the form of a rib having an
`inclined surface which gradually inclines downward from
`the upper portion of the inner surface of the reel hub 21
`toward the engagement projections 27, and the guide mem-
`bers 39 center the braking gear 42 when the outer periphery
`of the braking gear 42 is brought into contact with the
`inclined surfaces.
`
`As shown in FIG. 4, each gear tooth of the braking gear
`42 of the braking member 4 and each engagement gear tooth
`29 on the engagement projection 27 are triangular in cross-
`section. The gear tooth of the braking gear 42 has a first
`inclined surface 4211 which faces against the tape-unwinding
`direction U and abuts against a first inclined surface 29a of
`the engagement gear tooth 29 on the engagement projection
`27 which faces toward the tape-unwinding direction U, and
`a second inclined surface 42b which faces against
`the
`tape-winding direction W and abuts against
`a second
`inclincd surfacc 29b of thc cngagcmcnt gcar tooth 29 on thc
`engagement projection 27 which faces toward the tape-
`winding direction W. When the reel 2 is rotated in the
`tape—unwinding direction U with the braking gear 42 in
`mesh with the engagement gear teeth 29 on the engagement
`projection 27, the first inclined surfaces 42a of the gear teeth
`of the braking gear 42 are brought into abutment against the
`first inclined surfaces 29a of the engagement gear teeth 29,
`and when the reel 2 is rotated in the tape-winding direction
`W with the braking gear 42 in mesh with the engagement
`gear teeth 29 on the engagement projection 27, the second
`inclined surfaces 42b of the gear teeth of the braking gear 42
`are brought into abutment against the second inclined sur-
`faces 29b of the engagement gear teeth 29. Each of the gear
`tooth 42 and the gear tooth 29 is not larger than 90° in apical
`angle y, and the interior angle a between the first inclined
`surface 42a (or 29a) and the vertical S and the interior angle
`
`

`

`US 6,462,905 B]
`
`7
`
`[3 between the second inclined surface 42]) (or 291)) and the
`vertical [3 are not smaller than 30°. Further, the interior angle
`a for the first inclined surface 42a (29a) is not larger than the
`interior angle [3 for the second inclined surface 42]) (291)).
`That is, 60° Ev 2‘ 90°, 30°§ a§45°, and 30° 2‘ [3% 60°.
`Aprojection 44 extends upward from the upper surface of
`the disc portion 41 of the braking member 4, and a cross-
`shaped engagement groove 45 is formed in the projection 44
`to extend in the vertical direction. An engagement projection
`33 extending downward from the inner surface of the upper
`casing half 31 of the cartridge casing 3 is in engagement
`with the engagement groove 45 of the braking member 4,
`whereby the braking member 4 is held in the cartridge casing
`3 to be movable up and down but not to be rotatable.
`Acoiled spring (urging member) 5 is compressed between
`a portion of the upper surface of the disc portion 41 around
`the projection 44 and a spring retainer portion 34 formed on
`the upper casing half 31 around the engagement projection
`33, whereby the braking member 4 is urged toward the
`locking position where the braking gear 42 is engaged with
`the engagement gear teeth 29 on the engagement projections
`27.
`
`The releasing member 6 is disposed to be movable up and
`down between the braking member 4 and the bottom wall
`21a of the reel hub 21 and comprises a substantially trian-
`gular plate-like body portion 61. Acylindrical leg portion 63
`extends downward from the lower surface of the body
`portion 61 at each corner thereof. The leg portions 63 are
`passed through the through holes 26 in the bottom wall 21a
`of the reel 2 to be movable up and down. The engagement
`projections 27 are positioned between the leg portions 63
`outside the body portion 61 of the releasing member 6. The
`leg portions 63 may also be rectangular or ellipsoidal in
`cross-section.
`
`When the releasing member 6 is in its lowermost position
`shown in FIG. 1,
`the lower ends of the leg portions 63
`project downward form the lower surface of the reel 2
`through the portion at which the reel gear 24 is formed, and
`when the drive gear 13 is brought into engagement with the
`reel gear 24 in response to a chucking action of the reel drive
`means 11,
`the leg portions 63 are pushed upward by a
`predetermined stroke as shown in FIG. 2, whereby the
`braking gear 42 of the braking member 4 is disengaged from
`the engagement gear teeth 29 ofthe engagement projections
`27 and rotation of the reel 2 is permitted. Since the leg
`portions 63 are passed through the through holes 26 the
`releasing member 6 is rotated together with the reel 2.
`The reel 2 is provided with guide members 28 (FIG. 3)
`which guide the releasing member 6 when the leg portions
`63 are inserted into the through holes 26. Each of the guide
`members 28 guides a corner of the body portion 61 of the
`releasing member 6 and comprises a pair of guide ribs
`formed on the inner surface of the reel hub 21 to extend in
`
`the vertical direction near one of the through holes 26.
`Reinforcing ribs like the guide ribs are provided on the entire
`inner surface of the reel hub 21.
`
`Operation of the reel stopper means 10 will be described,
`hereinbelow. FIG. 1 shows a state of the magnetic tape
`cartridge 1 when it is not being used (e.g., when it is stored).
`In the state shown in FIG. 1,
`the braking member 4,
`the
`releasing member 6 and the reel 2 are held in the lower
`casing half 32 of the cartridge casing 3 under the force of the
`urging member 5 and the central opening 32a of the lower
`casing half 32 is closed by the reel 2. The releasing member
`6 is in its lowermost position where its lower surface is in
`abutment against the upper surface of the bottom wall 21a
`
`5
`
`20
`
`30
`
`35
`
`40
`
`45
`
`50
`
`60
`
`65
`
`8
`of the reel hub 21 and the lower end portions of the leg
`portions 63 project downward beyond the tips of the teeth of
`the reel gear 24. The braking member 4 is in abutment
`against the releasing member 6 and in its locking position
`where the braking gear 42 is in mesh with the engagement
`gear teeth 29 of the engagement projections 27 on the reel
`2, whereby rotation of the reel 2 is restricted and the
`magnetic tape is prevented from being drawn out.
`As shown in FIG. 2, when the magnetic tape cartridge 1
`is loaded in a tape drive, the rotary shaft 12 of the reel drive
`means 11 of the tape drive is moved toward the lower
`surface of the reel 2 and the drive gear 13 is brought into
`mesh with the reel gear 24 with the reel 2 slightly pushed
`upward, whereby the leg portions 63 of the releasing mem-
`ber 6 are pushed upward by the tips of the teeth of the drive
`gear 13. Thus, the releasing member 6 is moved upward
`overcoming the force of the urging member 5 and the
`braking member 4 is moved upward together with the
`releasing member 6, whereby the braldng gear 42 is disen-
`gaged from the engagement gear teeth 29 of the engagement
`projections 27 and rotation of the reel 2 is permitted. In this
`state, the braking member 4 in its upper position is away
`from the guide members 39 and does not restrict rotation of
`the reel 2 when the magnetic tape is loaded/unloaded.
`When the braking member 4 is moved downward from
`the releasing position to the locking position, the braking
`member 4 is centered by the guide members 39 on the reel
`2 so that the braking gear 42 is brought into mesh with the
`engagement gear teeth 29 with the braking member 4 held
`horizontal, whereby the braking member 4 is prevented from
`being inclined in the locking position. When the braking
`member 4 is subsequently moved upward to the releasing
`position by the releasing member 6, the braking member 4
`is held horizontal up to the releasing position. Accordingly,
`the phenomenon that the braking member 4 is inclined as
`shown in FIG. 5 can be suppressed, whereby the braking
`gear 42 is prevented from contacting the engagement gear
`teeth 29 to generate noise or to obstruct rotation of the reel
`2. Further, during assembly of the magnetic tape cartridge 1,
`the braking member 4 is automatically centered in the reel
`hub 2 by the guide members 39 and is incorporated in place
`in the reel 2, whereby assembly of the magnetic tape
`cartridge 1 is facilitated.
`Even if the guide members 39 are not provided, since the
`outer diameter D of the engagement gear formed by the
`engagement gear teeth 29 on the engagement projections 27
`on the reel 2 is larger than the outer diameter d of the braking
`gear 42 on the braking member 4, the braking member 4 is
`centered with respect to the reel hub 2 when it is moved from
`the releasing position to the locking position by Virtue of the
`difference in diameter so that the braking gear 42 is brought
`into mesh with the engagement gear teeth 29 with the
`braking member 4 held horizontal, whereby the braking
`member 4 is prevented from being inclined in the locking
`position.
`Further, when the reel 2 is rotated in the winding direction
`W due to drop impact or the like and an excessive winding
`force acts on the magnetic tape, the braking member 4 is
`moved upward along the first inclined surfaces 42a and 29a
`since the int