CA1077619A - Magnetic tape cassette - Google Patents

Abstract

MAGNETIC TAPE CASSETTE

ABSTRACT OF THE DISCLOSURE
A magnetic tape cassette is adapted to be used in a magnetic recording and/or reproducing apparatus provided with detecting means for detecting the ends of a magnetic tape in the magnetic tape cassette. The detecting means comprises a single light-emitting means and first and second light-receiving means respectively disposed opposite said light-emitting means. The magnetic tape cassette comprises first reel having a first hub and a second reel having second hub, an opaque magnetic tape having first and second transparent leader tapes provided at the opposite ends thereof and being connected at the opposite ends of the leader tapes to the first and second hubs, a cassette case for receiving and accomodating the first and second reels, and a lid hinged on the cassette case. The cassette case has first and second side walls respectively having a first and second windows formed therein, the first and second reels being interposed between said first and second side walls, a front face terminated at opposite ends by the spaced side walls, and a bottom face having a hole for receiving the light-emitting means. The lid swings between a closed position where the lid covers the front face and the first and second windows and an opened position where the lid exposes the first face and the first and second windows. The first window is formed in the first side at a position where the first window permits light passed through the first leader tape from the light-emitting means to reach the first light-receiving means when the lid is in the opened position. The second window is formed in

Description

~ 10~7619 ,' 1 1I BACKGROUND OF THE ~ENTION
This application is a divisional application of the I copending Canadian Patent Application Serial NoO 267,564, ¦ "DETECTION DE~ICE FOR DETECTING ENDS OF A CASSETTE TAPE~o The present invention relates generally to magnetic tape cassettes, and more particularly to a magnetic tape . cassette adapted to be used in a magnetic recording and/or l reproducing apparatus provided with detecting means for detecting the ends of a magnetic tape in the magnetic tape l cassette when the entire magnetic tape has been wound on a takeup reel or when the magnetic tape on ~ supply reel I cannot travel furtherO
There have been tape-end detection devices for detecting the completely wound state of a magnetic tape. In ,l a magnetic tape cassette adapted to be used in the tape-end detection device known heretofore, respective hubs of reels are formed from a transparent material and adapted to hold a I photocell. The tape end detection depends upon whether or :~ I not light is received fro~ a lamp positioned within the 1I cassetteO However, the constructions of the reels and cassette become complicated, since the photocell mounted on the side ! ~ of the recording and/or reproducing apparatus must be fitted ~ relatively into the cassette together with means for driving .1 1 the reelsO Moreover, since light must be detected after it ~ has been transmitted through a relatively thick reel hub, the tape end detection is inaccurate and unreliableO
In another known tape-~nd detection device, a photocell is disposed outside of the reel in a magnetic tape ¦ cassetteO The light from a lamp is shut off by the magnetic tape roll wo md up on the hub of the reelO ~ en the magnetic .~ ~ - 4 - ~
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1 tape hls been completely unwound and paid out, the light from the lamp reaches the photocell. However, since the magnetic tape is very thin, there is difficulty of positively detecting whether or not the magnetic tape has been wound around the hub of the reelO
Furthermore, the magnetic tape cassette used in this known detection device is provided in the vicinity of the central part of its side walls with openings (windows) for ~ permitting light from a lamp to reach a photocellO These windows are always open, even when the cassette is not being used, and the magnetic tape within the cassette is exposed through these windows to the outside. This is a disadvantageous feature of this cassette since dust can readily enter into Il the cassette through these windows and adhere to the magnetic tapeO Adhesion of dust on the magnetic tape gives rise to signal drop-out at the time of recording and reproducing, leading to a serious condition wherein good recording and reproducing cannot be accomplished.
I In addition, there are cases wherein these windows ~¦ become clogged by dust, grime, or like foreign matterO In other instances, labels with the recorded contents of the ¦ cassettes printed or written thereon have been stuck on the ¦ side walls of the cassette cases, thereby closing the windows, either because of carelessness of the users or because users, ~ in general, do not fully understand the construction of the cassette. In such a case, the passage of the light from the lamp is obstructed, and this gives rise to a serious disadvantage in that tape-end detection becomes impossibleO
In still another known tape-end detection device, 3~ j s so-cslled ompsct type cassette, wherelr an audio sitnal . -.
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1~r765~3 1 is recorded on or reproduced from a magnetic tape in a state in which it is accommodated within the cassette, is used, and light from light-emitting means inserted in the cassette passes through a transparent leader tape fixed to the tape end part when the tape end is reached and is projected onto light-receiving means provided on the outside of the front . face of the cassette in a position to confront the light-emitting me~nsO
l This magnetic tape cassette, however, is adapted - 10 ~ to carry out recording and reproducing only an audio signal I with the magnetic tape always in a state wherein it is I accommodated within the cassette. For this reason, this magnetic tape cassette cannot be applied to ~n apparatus for ll recording and/or reproducing a video signal b~ drawing the 15 ll magnetic tape out through the front face of the cassette and passing it in wrapping contact around a guide drum having rotating headsO The reason for this is that, in an apparatus of this character for recording/reproducing video signals, l~ means for drawing the magnetic tape out of the cassette through 1 the front face thereof is provided, and, for this reason, ~ if light-receiving means were to be provided to confront the I ~ cassette front face~ this light-receiving means would interfere with the operation of the tape dr~wing out means. Furthermore, ~ sin~e it is necessary to provide a pair of light-emitting 25 ~ means respectively in separate positions to confront a ~ `
~ pair of light-receiving means, the construction becomes :: complicated O

¦ SUMM Y OF THE INVENTION
: 30 Accordingly, it is a general object of the present 1 invention to provide a novel and useful magnetic tape cassette adapted to be used in a magnetic recording and/or reproducing apparatus provided with a device for detecting the ends of a magnetic tape, which overcomes the above described difficulties.
Another and specific object of the invention is to provide a magnetic tape cassette adapted to be used in a magnetic recording and/or reproducing apparatus provided with a~device for detecting the ends of a magnetic tape by ; 10 1 detecting light transmitted through transparent leader tapes.
The magnetic tape cassette has a cassette case provided with I windows in side walls thereof and a lid hinged on the side wallsO The lid covers the magnetic tape exposed on the Il front face of the cassette case and the windows provided in ~ the side walls in its closed positionO In the magnetic tape cassette according to the invention, since the windows provided in the side walls of the cassette case are closed by a lid when the cassette is not being used, infiltration of dust and other foreign matter through the windows into the ~ cassette interior is prevented. Therefore, there is no possibility of dust adhering to the magnetic tape to cause ¦ signal drop-out at the time of recording and reproducing, and ; ¦ other undesirable effects such as generation of noise and deterioration of image quality do not occur. Furthermore, ~ clogging or shutting of the windows by other objects is also p~e~e~, and positive detection of the tape end can always be ~ a~complished.
I ¦ Still another object of the invention is to provide a 1 magnetic tape cassette which is suitable for use in conjunction with the above mentioned detection device, in which positions ~ - 7 -: :~

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.. .. .. : ., . . .. - -" I 1077~ 9 ll 1 ~ and configurations such as the hole for acco~nodating the light-emitting means and the above mentioned windows for passing light are optimally selected, and which as a whole has been miniaturized.
Further objects and features of the invention will be apparent from the following detailed description with respect to preferred embodiments of the invention when read in con~iunction with the accompanying drawings, briefly described belowO
10 1l RIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. l is a perspective view of the bottom of one l embodiment of a magnetic tape cassette according to the I present invention;
FIGo 2 is a plan view of the magnetic tape cassette illustrated in FIGo l, which is shown with a part cut away, in I a state wherein it has been loaded in an example of a magnetic l -; ll tape recording and/or reproducing apparatus provided with 1 a tape-end detection device;
FIGSo 3A and 3B are fragmentary plan views respectively showing the manner in which the cover of the magnetic tape cassette is locked and unlocked; and FIGS. 4A and 4B are plan views of the magnetic tape ~ cassette, with the upper half of its case removed, respectively showing the magnetic tape end upon completidn of the fast-iorward and ewind modes oi operation.

~ DETAILE~ DESCRIPTION
One embodiment of a magnetic tape cassette of the I
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~ 10776~9 1 present invention for cooperating with a device for detecting an end of a magnetic tape has a construction as shown in 1i FIGS. 1 and 2. The magnetic tape cassette 10 has an outer housing structure comprising a cassette case 11 and a lid 120 The lid 12 is freely openable and closable on the front face of the case 11. The cassette case 11 has side walls lla and llb, spaced apart front and rear face parts llc and lld respectively terminated at opposite ends thereof by the side walls, and upper and bottom parts lle and llf covering the upper and lower portions of a spa~e enclosed within and by the side walls and the front and rear face partsO The cassette case 11 accommodates therewithin, a freely rotatable tape supply reel 14 and a tape takeup reel 15 each for winding an opaque magnetic tape 13, side by side between 1I the side wallsO The bottom part llf of the cassette case 11 has ll two shaft holes 17 and 18 for receiving reel drive spindles ~ll or shafts on the recording and/or reproducing apparatus 16 0 : These shafts fit into the hubs of the respective reels 14 ! ~l and lS when the cassette 10 is inserted into its loaded l position in the recording and/or reproduc~ng apparatusO
¦~ As shown in FIGSo 4A and 4B, one end of the magnetic tape 13 is connected to the outer end of a transparent leader tape 20 which if fixed at its inner and to a.hub 19 of the ~ supply reel 14. The other end of the magnetic tape 13 is ~ connected to the outer end of a transparent leader tape 22 which is fi~ed at its inner end to a hub 21 of the take~p reel 150 The magnetic tape 13 is guided by guide poles 23, ¦ 24, and 25, from the supply reel 14 to the takeup reel 15 during normal recording, reproducing, or fast-forwarding mode operetions, d from the tekeup reel 15 to the aupply reel :' ,; _ g_ ~:~ ~
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lo776,~9 n~ o.~e ~-p e ra f/ o r~ j l 14 during rewinding~
Within the cassette case 11, a hole 26 for receiving a lamp is formed in the bottom part llf at a substantially inter- j mediate position between the two reels 14 and 15 and near the front face side of the caseO This position is advantageous in that it is in a relatively clear and ample space within the cassette case. For this reason, there is no necessity of providing an additidna~ space especially for the provision , of the lamp fitting hole 26, and the cassette case need not be made large merely for this purposeO This lamp fitting hole 26 is defined and bordered by a cylindrical wall 27, in which openings 27a and 27b are formed. Furthermore, at specific positions of wall structures within the case ll, l, cutouts or openings 28, 29, 30 and 31 are formed.
1~ Windows 32 and 33 are respectively provided in the side walls lla and llb of the cassette case 11 at positions ¦! near the front face, that is, at the front parts of the side walls near their parts adjacent the front face.
The above mentioned openings 27a and 27b are provided ~ at positions where straight lines joining the space (chamber) ; ~ within the cylindrical wall 27 and the windows 32 and 33, respectively, intersect the cylindrical wall 27. The configura-tions of the part of the cassette interi~rrare so designed that the a~ove mentioned straight lines (i.e., the light paths they represent) do not touch or intersect the hubs 19 and 21 of the reels 14 and 15. A light-emitting element described here-inafter is fitted into the interior space of the cylindrical wall 27. The light emitted by this light-emitting element ~ is directed toward the windows 32 and 33 only upon passing through the penings 27a aDd 27b in the cylindrical wall 27, I
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,,,, ,, ` ~ 1077619 1 1 and emission of light in unnecessary directions is prevented.
Therefore, there is no possibility of light scattering and being reflected in unnecessary directions and, without beingl blocked by the magnetic tape, passing through the windows to cause erroneous detection operation.
In the recording and/or reproducing apparatus 16, a light-emitting element, eOg., a lamp 34, fi~s into the hole 26 when the magnetic tape cassette 10 is inserted into its l loading positionO In the recording and/or reproducing apparatus ; 10 j 16, a light receiving element, eOgO, a photocell 35, is positioned to receive light emitted by the lamp 34 which passes through the openings 27a and 28 and the window 32.
In addition, a photocell 36 receives the light emitted by ¦I the lamp 34 which passes through the openings 27b, 29, 30, 1 and 31 and the window 33.
Il The lid 12 comprises a main lid structure of plate 'I I form facing the front face part of the cassette case 11 and side I face flanges or side parts 12aaand 12b formed integrally with this main lid structure by ~b~nding at its opposite ends. The lid 12, i at its side parts 12a and 12b, is pivotally supported by hinge pins 40 and 41 on the side walls of the cassette case 11 near the front face part. The lid 12 is continually urged to swing toward a closed position by a torsion spring 42 around the pivot pin 41. When the magnetic tape cassette 10 is not loaded in the apparatus 16, the lid 12 is closed as, l indicated by broken lines in FIG. l,to cover the magnetic '; ~ tape 13 which is exposed at the front face of the cassette case 11. When the lid 12 is closed, the windows 32 and 33 are covered by the side parts 12a and 12b of the lid 12, to prevent infiltration of dust into the cassette case and :
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107 7~i9 1 adherence of ~ust to the magnetic tape. Furthermore, there is almost no possibility of closure of the windows 32 and 33 by dust or grime or by labels stuck thereover because of a reason such as carelessness on the part of the user.
Here, the windows 32 and 33 are provided in the side walls of the cassette case 11 near the front face part thereof,ta~d since the side parts 12a and 12b of the lid 12 need to be of a size which is sufficient merely to cover the windows 32 and 33 when the lid 12 is closed, the lid l 12 can be made small.
Within the case 11, a lock ~ee 43 is rotatably supported by pivot pins 44a and 44b and urged byda torsion spring 45 to press against the inner surface of the case side 1 wall. The lock plate 43 has an opening 46. Projections 47 and 1l 48 on the side surface of the lock plate 43 project through openings in the side wall of the case. The projections 47 engages¦
a recess 49 in the side part 12b of the lid 12, when it is closed "I
thereby locking the lid 12 against opening~ The projection 48 is disposed within a groove formed between the side part 12b ¦ of the lid 12 and the outermost surface of the case 11 when the lid 12 is closed.
The magnetic tape cassette 10~ with its lid 12 closed, is inserted horizontally in the arrow direction A
onto and along a loading platform 50 of the ~ecording and/or l reproducing app~ratus 16, as indicated in FIG. 3A. A leaf ¦ spring 51 has a projection 52 at its free end and is fixed ¦ at its root end to the side of the loading platform 50. As ~ ¦ the magnetic tape cassette 10 is inserted,dthe projection 52 j~ ~ slides ald~ the side part 12b of the lid 120 When the ; ! magnetic tape cassette 10 is fully inserted as shown in .

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~ 77619 1 ~I FIG 3B, the projection 52 fits into the groove between the side part 12b of the lid 12 and the outermost surface of l.
the case 11 and presses the projection 48 toward the left as viewed in the same figureO As a consequence, the lock . ~ I
plate 43 rotates, overcoming the force of the spring 45. The projection 47 is also displaced left~rd and is disengaged fromtthe recess 49 of the side part 12b of the lid 12, thereby ii . ~ unlocking the lid 12.
1 Then, when the loading platform 50 is thereafter lowered, a lug 53 for opening the lid fixedly provided in p the recording/reproducing apparatus fits relatively into a groove part 63 provided vertically from the lower surface at a position near the side wall llb in the front face part ¦ of the cassette case 11 and abuts against the ~wer edge of 1I the lid 12. Together with the downward movement of the 1 I cassette 10, the lid 12 engages the lug 53 and opens against : Il the force of the spring 42, as indicated by full lines in FIG. 1. Consequently, the front of the magnetic tape 13 is ~ revealed, and the windows 32 and 33 open?

- 20 ~ On the downward movement of the cassette 10, the ¦ lamp 34 is fitted into the hole 26, and the reel drive shafts (not shown) are fitted into shaft holes 17 and 18. At the same time, a capstan 55 fits into a recess 54 on the front side and lower side of the case 11~ Magnetic tape drawing out and loading ~embers 58 and 59 fit into recesses 56 and 57~
When the recording and/or reproducing apparatus 16 ¦ . is placed in the recording or reproducing mode of operation, ¦ -; the upper drum of a guide drum 60 having video heads begins to rotate. At the same time, the magnetic tape drawing out and -.13 -; .~ ll ~ I
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10~7619 loading members 58 and 59 move to the positions indicated by broken lines. The magnetic tape 13 wraps around part of the guide drum 600 A pinch roller 61 presses the magnetic ~ tape 13 against the capstan 55.
The magnetic tape 13 thus clamped by the capstan 55 and the pinch roller 61 is driven by the rotation thereof.
The tape on the supply reel 14 is unwound and paid out to be wound up on the takeup reel 15. At the same time, video signals are recorded on or reproduced from the magnetic tape 13 10 ;~ by the video heads of the guide drum 600 An audio signal is recorded or reproduced by an audio head 62.
During the recording or reproducing operation, the light from the lamp 34 is shut off by the magnetic tape 13 paid out or supplied from the supply reel 14 and wound or 15 I taken up by the takeup reel 15. Thus, light does not reach f ~I the photocells 35 and 36.
~hen the magnetic tape 13 has been completely paid out from the supply reel 14, and the recording or ~ reproducing has been completed, the transparent leader tape 1 20 is paid out into the tape travel path between the reel hub 19 and the guide pole 240 Consequently, the light from the lamp 34, which until now has been shut off by the opaque ¦ magnetic tape 13, passes through the leader tape 20 and the ¦ window 32, reaching the photocell 35. This reception of the ¦ light by the photocell 35 means the detection of the end of the tapeO The resulting output detection signal of the photocell 35 ~tops the recording or reproducing operation.
The fast forwarding mode operation is carried out , I with the tape 13 accommodated within the case 11. Upon I completion of this fast forwarding mode operation, as indicated ; - 14 -, "
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~077~19 1 ¦~ in FIG. 4A, the light from the lamp 34 passes through the leader tape 20 and the window 32 and is received by the photocell 35O The fast forwardi~g mode of operation is thus stopped. The length of the leader tape 20 is selected at a length, for example, such that the leader tape 20 cut across the path of the light from the lamp 34 to the photocell 35, but it does not reach a position which cuts across the path of the light from the lamp 34 to the photocell 36.
~. ' The rewinding of the magnetic tape 13 is also carried out with the tape accommodated within the case 11.
As shown in FIGo 4B, upon completion of the rewinding operation, the transparent leader tape 22 is paid out into the tape travel path between the reel hub 21 and the guide pole 250 As l, a consequence, the light from the lamp 34, which until now I has been shut off by the opaque magnetic tape 13, passes through the leader tape 22, the openings 30, 31 and 46, and the window 33 and reaches the photocell 36. This reception of the light by the photocell 36 means the detection of the end of the tape which has completed its rewindingO The ¦ resulting output detection signal of the photocell 36 stops ¦ the rewinding operation. The length of the leader tape 22 is selected at a length, for ~ample, such that the leader tape 22 cuts across the path of the light from the lamp 34 to the photocell 36, but not to cut across the light path of the lamp 34 to the ~ photocell 35O In FIGS. 4A and 4B, parts of the magnetic tape 13 and the leader t~apes 20 and 22 are shown twisted, but only for ex~lanation purpose For the light-emitting means, an arrangement wherein light-emitting elements such as a pair of photodiodes ~ respectively with their light emitting surfaces facing the ,..

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1~776~9 .
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1 ~ photocell 35 and 36 are provided at the position of the lamp 34 may also be used instead of using a single lamp.
In each of the a~ove described embodiments of the invention, the light-emitting elements are not limited to lamps but may take other forms that emit light. Fur?thermore, the light-receiving elements are not limited to photocells, , but may be other elements which receive light and convert it into electric signalsO
The tape-end detection signal can be used not only l as a signal for stopping the recording and/or reproducing ; apparatus but also for changing the operational mode thereof, such as from the recording or reproducing mode to the rewinding mode or from the rewinding mode to the recording or reproducing modeO
15 I Further, this invention is not limited to these embodiments thereof. Variations and modifications may be made without departing from the scope and spirit of the ~¦ invention.
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Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A magnetic tape cassette for use in a magnetic recording and/or reproducing apparatus, said cassette compris-ing: case means having spaced parallel side walls, a front face, a back wall, and upper and lower panels; first and second reel means respectively having first and second hubs, said first and second reel means being accommodated in a side-by-side rela-tionship within said case means and between the side walls; an opaque magnetic tape extending along a tape travel path between the first and second reel means, and having first and second transparent leaders connected from the opposite ends of said opaque tape to the first and second hubs, respectively, to be wound around the first and second reel means; lid means for covering a part of the magnetic tape on the front face of said case means and for covering the front end portions of the side walls in the vicinity of the front face of said case means;
hinge means mounted respectively on the front end portions of the side walls for enabling said lid means to swing between closed and opened positions to cover or expose the front end portions of the side walls and to cover or expose the part of the magnetic tape on the front face; means forming a light inlet hole in the lower panel of said case means at a position near the front face and substantially intermediate the first and second reel means; and first and second window means forming outlets of light paths extending from said light inlet hole across the tape travel path to said first and second outlet window means, said first and second window means being formed in the front portions of the side walls at positions near said hinge means, and said first and second window means being exposed or covered by said lid means when said lid means is in its opened and closed positions respectively.

2. A magnetic tape cassette as claimed in claim 1 in which said light inlet hole is positioned so that straight lines passing through the centers of the first and second window means to said light inlet hole do not intersect said first and second hubs.

3. A magnetic tape cassette as claimed in claim 1 and a hollow cylindrical wall, the light inlet hole formed in the lower panel of the case means being encompassed by said hollow cylindrical wall extending upwardly from the rim of the hole in the lower panel and into the interior of the case means, the cylindrical wall having first and second openings forming light inlets for directing light along first and second straight lines extending from the interior space within said cylindrical wall to the first and second window means respectively.

4. A magnetic tape cassette as claimed in claim 3 in which the lengths of the leaders are such that said first leader tape reaches a position which cuts across said first straight line but does not reach a position which cuts across said second straight line, and, moreover, the second leader tape reaches a position which cuts across said second straight line but does not reach a position which cuts across said first straight line.

5. A magnetic tape cassette as claimed in claim 1 in which the cassette case has a slot for insertion therethrough of a lide opening lug provided in said apparatus thereby to open said lid, and said slot is formed perpendicularly at the front face part in the vicinity of one side wall of the cassette case.

6. A magnetic tape cassette as claimed in claim 1 in which the case means has two recessed parts formed in positions which are near each other and extend from the lower panel to the front face of the case means to enable the magnetic tape to be drawn through said recessed parts and out of the case means when said lid means is in the opened position.

7. A magnetic tape cassette as claimed in claim 1 in which said lid means comprises a main lid part which covers the front face of the case means when said lid means is in said closed position, said lid means further comprising opposed side parts angularly formed integrally with the main lid part at the opposite ends thereof, said opposed side parts covering the front end portions of the side walls of the case means to shut off the first and second window means when the lid means is in said closed position.

8. A magnetic tape cassette as claimed in claim 1 further comprising means for guiding the magnetic tape with the attached leaders along a tape travel path which passes said first and second window means so that the magnetic tape is exposed through said first and second window means when said lid means is in the opened position and is shut off from said first and second window means when said lid means is in the closed position.