NZ211054A - Flexible magnetic disk:preventing radial displacement during rotation - Google Patents

Description

211054 Priority Date{s): Complete Specification Filed: 7.3.7%i. Class: . .0.1 IK> Publication Date: .-IAN, P.O. Journal, No: .J.Q IS.

Wder lation 23 (I) the CpnnpWle • Specification sss been ante-data to .3 Ag.^uS.1 |9^t. fiX^ % // " f/'V .'"Y e n yr<\ % -A T'l V, $WCTi^' NEW ZEALAND Divided out of: PATENTS ACT, 1953 No.: 197 ,970 Date: 7th August 1981 COMPLETE SPECIFICATION "FLEXIBLE MAGNETIC DISK CASSETTE" EVWe, SONY CORPORATION, a corporation of Japan, of 7-35 Kitashinagawa, 6-chome, Shinagawa-ku, Tokyo, Japan, hereby declare the invention for which £%/ we pray that a patent may be granted to ncae/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - (followed by page la) 2 1 1054 BACKGROUND OF THE INVENTION Field of the Invention: This invention relates to a flexible magnetic disk cassette in which a flexible magnetic disk is rotatably accommodated, and relates to a recording and/or reproducing apparatus for the same Description of the Prior Art: As a positioning (centering) unit for a magnetic disk having concentric or spiral recording track, there has heretofore been known such a positioning unit as shown in Fig. 1. Referring to Fig. 1 for illustration of a conventional positioning unit of this sort, a disk cassette 1 comprises a ' ■ cassette cover 4 in the form of a rectangular parallelopiped composed of upper and lower halves 2 and 3, and a flexible sheet-like magnetic disk (magnetic sheet) 5 rotatably accommodated within a space 4a of the cassette cover 4.

The magnetic disk 5, for example, has magnetic surfaces formed on both upper and lower surfaces thereof and also has a disk mounting aperture 6 formed in its central part. On the other hand, in an upper plate2a and a lower plate 3a of the disk cassette 1 there are formed a pair of upper and lower air inflow apertures 7 and 8 in corresponding relation to the disk mounting aperture 6, and air outflow apetures 9 and 10 in four points of the circumferential part of the 'space 4a, and further a pair of upper and lower head insertion apertures 11 and 12 constituted of apertures extending radially of the space 4a, respectively.

The disk cassette 1 is installed (loaded) by a I - 1 Or 2 1 1054 guide member 14 onto a predetermined position of a magnetic recording and reproducing apparatus, and the magnetic disk is fixed to a disk rotating shaft 17 by being chucked between a driving shaft 15 and a presser member 16 at the portion of the disk mounting aperture 6, whereby the magnetic disk 5 is positioned with respect to the-(driving shaft .

On the other hand, into the head insertion aperture 12 below the disk cassette 1 there is inserted a magnetic head 18, which is brought into contact with the lower magnetic surface of the magnetic disk 5.

In such a cassette loaded state, the disk rotating shaft 17 is rotated by. a motor 19 whereby the magnetic disk 5 in the disk cassette 1 is rotated, and in association therewith the magnetic head 18 is moved in a radial direction of the magnetic disk 5 to perform a desired recording or reproducing operation.

However, in case the magnetic, disk 5 is a flexible sheet-like disk, the disk mounting aperture 6 in the magnetic disk 5 may partially be torn up and deformed as shown in Fig. 2, or the peripheral edge portion of the aperture 6 may be damaged by the driving shaft 15, when mounting the magnetic disk 5 on the driving shaft 15. Once the aperture 6 is so deformed or damaged, it becomes impossible to effect positioning, namely centering, of the magnetic disk 5 with respect to the driving shaft 15 with high accuracy. As a result, at every installation (loading) of the magnetic disk 5, its position with respect to the driving shaft 15 varies, and this impedes a high accuracy reproduction. The conventional positioning mechanism shown has involved such an 2 1 10 54 inconvenience.

Though not shown, moreover, there also is known a positioning unit wherein a reinforcing ring formed of a metal or synthetic resin is attached to the center aperture of a magnetic disk. Also in this case, however, it is very difficult to avoid a positional .shift .of the magnetic disk when installed, namely an amount of deviation of the center of the magnetic disk with respect to the axis of the driving shaft, within the tolerance of the diameter of the driving shaft and that of the above center aperture.

Consequently, the conventional positioning system just mentioned above has involved an inconvenience such that every time the magnetic disk is installed there occur vaxiations in its installed position, so it is impossible to install "the magnetic disk always in the same state with respect to the driving shaft, and that the positional shift of the recording track on the magnetic disk with respect to the.(driving shaft is too large. So there oGC-ua tracking error noticeably, which impedes the attainment of a high density recording track.

OBJECTS AND SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible magnetic disk cassette and a recording and/or reproducing apparatus for the same, wherein a flexible magnetic disk accommodated in the disk cassette can be driven in highly accurate positioned state.

More specifically, it is an object of the present invention to provide a flexible magnetic disk cassette and a recording and/or reproducing apparatus for the same, by which it is possible to minimize tracking error and thereby 2 t1054 to perform a high density recording and reproducing operation.

Accordingly in one aspect the invention consists in a flexible magnetic disk cassette comprising: (a) a flexible magnetic disk; (b) a pan-shaped one-piece center core disk of magnetic material having a center hollow and raised fringe, said center core disk attached at a center of said flexible magnetic disk by said raised fringe; and (c) a cassette cover having an upper half and lower half containing said flexible magnetic disk with said center core disk, said lower half having a driving aperture larger than an outer diameter of said center hollow of said center core disk.

In another aspect the invention consists in a magnetic disk cassette comprising: a flexible magnetic disk; a center core disk attached and positioned 1n an aperture at a center of the flexible magnetic disk; the center core disk having an annular center hollow; and a cover having an upper wall and lower wall between which the flexible magnetic disk is positioned, the upper wall having a ring-like projection receivable 1n the annular hollow of the center core disk when the magnetic disk is assembled in the cover, the lower wall having a driving hole for access to the center core disk by a driving mechanism.

Preferably a cassette wherein the center core disk at least partially extends Into the driving hole, the driving hole having a diameter slightly larger than an outer diameter of the annular hollow of the center core disk.

Other objects, features and advantages according to the present invention will be apparent from the following detailed description of illustrative embodiments shown In the accompanying drawings. 2 11054 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal sectional view schematically showing an installed state of a conventional disk cassette on a conventional magnetic recording and/or reproducing apparatus; Fig. 2 is an enlarged longitudinal sectional view of a main part showing the relationship among a magnetic disk, a driving shaft and a presser member.

Fig. 3 is an exploded perspective view of a disk cassette according to the embodiment of this invention; Fig. 4 is a perspective view of an upper half of a cassette cover viewed from below; Fig. 5 is a plan view of a center core .'.disk viewed from a recessed side thereof; Fig. 6 is a perspective view of the disk cassette viewed from below; Fig. 7 is a longitudinal sectional view of a main part of the disk cassette showing its central portion, partly omitted; Fig. 8 is a longitudinal sectional view of a main part of the disk cassette showing a guide means comprising a guide groove formed in the cassette cover and a pawllike projection formed on a shutter; Fig. 9 and Fig. 10 are each a longitudinal sectional view of. .a main part of the disk cassette showing a modification of the guide means; Fig. 11 is.a longitudinal sectional view of a main part of the disk cassette showing an erroneous erase preventing detent formed on :the cassette cover; Fig. 12 is am exploded perspective view showing 2 1 t 0 54 the disk cassette and a main part of a recording and/or reproducing apparatus according to the embodiment of this invention, onto which is to be installed the disk cassette; Fig. 13 is a plan view of the above apparatus with a cassette presser member removed; Fig. 14 is a plan view of the apparatus with the cassette presser member; Fig. 15 is a sectional view taken on line XV - Xv of Fig. 14; Fig. 16 is a sectional view taken on line XVI - XVI of Fig. 14; Fig. 17 is a sectional view taken on line XVII - XVII of Fig. 14; Fig. 18 is an exploded perspective view showing a mounting state of a rotor of a motor, a spacer, a leaf spring to which is attached a spring-biased driving pin, a yoke and a motor cover; Fig. 19 is a sectional view taken on line XIX -XIX of Fig. 13; Fig. 20 and Fig. 21 are sectional views similar to Fig. 19 illustrating the operation of the spring-biased driving pin; Fig. 22 is an exploded perspective view of a main part of a bead moving mechanism; Fig. 23 is a perspective view of a rotational position detecting mechanism for the motor shaft of a step motor; Fig. 24 is a sectional view taken on line XXIV -XXIV of Fig. 22; Fig. 25 is a sectional view taken on line XXV - 2 1 10 54 XXV of Fig. 24; Fig. 26 is a longitudinal sectional view of a main part illustrating a correlative operation between the erroneous erase preventing detent of the disk cassette and an erroneous erase preventing detent detection member; Fig. 27 is a schematic side view illustrating the principle of a correcting operation against an inward warp of upper and lower plates of the cassette cover; Fig. 28 is a plan view of the center core disk in a positioned state with the motor shaft and the spring-biased driving pin respectively inserted in the motor shaft insertion opening and the spring-biased driving pin insertion opening both formed in the center core disk.

Fig. 29 .and Fig. 30 are plan views similar to Fig. 28 each showing a modification of the center core disk; Fig. 31 is a plan view similar to Fig. 29 illustrating a modification-of the positioning mechanism of the center core disk; Fig. 32 is a plan view of a yoke illustrating another modification of the positioning mechanism of the center core disk; and Fig. 33 is a longitudinal sectional view of a part of a driving mechanism illustrating still another modification of the positioning mechanism of the .center core disk. ; 2 1 10 54 DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this invention will be described with reference to Fig. J to Fig. .

In this embodiment, a flexible magnetic disk cassette containing a sheet-like flexible magnetic disk is installed onto a recording and/or reproducing apparatus and .recording and/or reproducing operation is performed.

First, an explanation is here given to a disk cassette 26 comprising a flexible magnetic disk 21 and a cassette cover 22. As shown .in Fig.3, the flexible magnetic disk 21 t \ V I - to be continued. - 2 2 1 10 54 is formed of, for example, a thin disk-like high polymer film having a thickness of 0.4 mm, and a magnetic layer is uniformly formed on both surf aces" to which a recording/reproducing magnetic head is to be brought into contact.

At the center of the flexible magnetic diski/ there, is formed a circular center opening i/a (see Fig. ?) at which there is attached a center core disk made of a ferromagnetic material such as iron. The center core disk i3 is iorme.i ^by pressj from a .flat disk and, as shown in Fig. ^ and Fig. on one side thereof there is formed a center hollow^3a and on the other side thereof there is formed a disk-like convexed portioni3b, while a-t -the peripehral edge portion of the center core disk-*3 there is formed a ring-like raised 15 fringe23c. Thus the center core disk ^3 is constituted in the form of a pan. As shown in Fig. 7/ a ring-like double-sided adhesive sheet 2J is bonded to y Y~±he raised fringe.^ c of the center core disk , and the peripheral edge portion of the center opening x/a of the magnetic disk is bonded to the double-sided adhesive sheet XJ, whereby the center core disk ^3 and the flexible magnetic disk i/ are joined together integrally.

At a nearly central part of the center core disk , a square center aperture formed as a motor shaft insertion aperture, and at a position which is distant by a predetermined distance from the ' center aperture a rectangular driving and positioning aperture is formed as a positioning-pin insertion aperture. As clearly shown in Fig. the • center 0^ of the center aperture Xtyis off the center 02 9 of the center core disk ^3 and the flexible magnetic disk. and is slightly distant by a predetermined distance toward the driving and positioning apeatureif". The center aperture X1/ and the drivng and positioning apeature are formed so that a pair of diagonal lines d^ and d^ of the center aperture are each parallel with short and long side portions i£b and zta of the driving and positioning aperture if, respectively- Furthermore, the length of one side of the center aperture X1/- is slightly larger than the diameter of the motor shaft I ^ On the other hand, the cassette cover22. for ; accommodating the flexible magnetic disk.2/, as shown in Fig. 3 , is composed of an upper halfj&a and a lower half « I 2ib which are made of, for example, an injection molded k 25 WJ article from ABS resin containing an antistatic agent. i . The outer peripheral portions of the upper and lower j halves^a and22b are welded to each other to form a flat j rectangular cassette. At a nearly central part of lower I half 22b there is formed a circular center opening 28 as a driving hole, and at the peripheral edge portion of the driving hole 28 and on the inner in 3 2 1 10 54 surface of the lower half ,22b there is integrally formed a ring-like projection^. As shown in Figs. 6 and 7, the convexed portion23b °f center core disk 23 is inserted in the driving hole ^ in a state having-a slight looseness.

On the inner surface of the central part of the upper \Figs.4 and?7 half22a, as shown irvei^r^T^there is integrally formed a ring-like projection , and also around the projection there is integrally formed a ring-like projection .?/ which is concentric with the projection^. The projecting length of the projection 3(? is longer than that of the projection £/ and hence, as shown in Fig. 7# t*10 projection $0 extends beyond the projection .)/ and projects on -.the inner surface side of the lower half22b. The ring-like projection. $C> is inserted in the center ±=>llow23i of the center core disk 23 in a state haivng a i ght looseness.

Now, the cassette case.22, the upper and lower halves^ a and22b, the center core disk .23 and the ring-like projection of the upper half22a are, for example, in the following diemnsional relation. The thickness of the cassette case22 is 3.4 mm, the thickness L2 of an upper plate^2c and that of a lower plate2ic of the upper and lower halves22a and22b are each 0. 8 mra respectively, the thickness L, of the upper plate22.£ of the upper half22a of the portion surrounded with the projection 3# is 1.0 nun, the projecting leng-th of the projection $0 is 1.5 mm, the thickness of the center core disk .13 is 0. 3 mm, the thickness Lg of the lower plate22& of the lower halfiib adjacent to the center opening i^is 1.3 mm, and the height of the center core 11 2 110 54 W • ( disk -23 is 1.8 mm (see Fig. 'J) .

When the disk cassette is installed onto the recording and/or reproducing apparatus as will be described later, the flexible magnetic disk 2/ is diposed nearly centrally in the direction of the thickness of the cassette cover as shown by the solid line in Fig. and then is rotated. In this case, the distance L0 O between the fringe2Bc °f the center core disk23 and the inner surface of the upper half22a and the distance L0 between the flexible magentic disk 2/ and the projection 2^ of the lower half .22b are each 0.4 mm. The distance L^0 between the-.tip end of the projection $0 of the upper half22a and a lower surface23d of the center disk 23 is 0.4 mm, and the distance between the outer surface of the lower half22b and the lower surface i^d of the center core diskJ3 is 0.2 mm (see Fig.^ ).

When the disk cassette is .not in use, the center core 0(1; disk 23 and the flexible magnetic disk2/\ts'placed cn the lower half2ib by virtue of their, own weights, for example, as shown by dot-dash line in Fig. 7. In this case, the tip end portion of the projection of the upper half 22a. and the projection 2^ of the lower half 22b overlap with each other by 0.4 mmCdistance so even if the center core disk-^3 is moved, a part of the center hollow J$a of the center core disk 23 is sure to « k \ (J lA ^ engage the projection . Thereby the Wioutn- of looseness in a planar direction of the center core disk23 and hence the flexible magnetic disk2/ is kept within a predetermined range, and therefore the projection $0 and the center . hollow2^3 of the center core disk 23 are not disengaged ( * from each other along with the displacement of the center core disk 23- In case the disk cassette 2^ is turned upside down from the state shown in Fig. 7 and consequently the center core disk .23 is placed on the upper half22a by virtue of its own weight, the projection comes into a completely fitted state within the center hollow^?a of the center core disk.23/ so that, as in the aforesaid case, the amount of displacementof the center core disk ^3 and hence of the magnetic disk _}/ is kept within a predetermined range.

In the disk cassette^ having the above const-tuction, the amount of displacement of the center core disk 23 and of the flexible magnetic disk xj can be regulated exactly by the projection until gap between the upper and lower plates^c and22d becomes wider by 2.2 mm (the sum of the overlapping length of 0.4 mm and the center core disk height of 1.8 mm) while the upper and lower halves22^ and22b are moved from the state shown in Fig. 7 toward the .exterior, namely in the direction in which the upper plate 22c and the lower plate iid go a^way from each other.

On the inside surfaces of the upper and lower halves22a and 22b there are integrally formed, four arcuate ribs and respectively extending concentrically with the driving hole 2$ at regular intervals.

When the cassette cover 22. is assembled^ * - - >fthe "ribs 33 of the upper half25a and the ribs of the lower half22b are disposed on the same circumference, and at the same time the .ribs 33 and 3ft. are positioned adjacent to each, other at • I I 13 the four corners •'the-.caasettE-cover 22 whereby there is \ pair of J formed substantially one' rib at each corner. The flexible magnetic disk 2.1 is disposed so as to be surrounded with these ribs .53 and )$. . The ribs 33 abut the inner surface of the lower plateiid of the lower halfiib and the ribs abut the inner surface of the upper plate22c Df the upper halfZJa. Thereby the cassette cover22, which is flat and easy to be deformed even by a small external force, is mechanically reinforced. Furthermore, in order to avoid possible damage or wear of the flexible magnetic disk2/, a magnetic disk protecting non-woven fabric is attached by heat-weld or a like means between the projection 3/ and the ribs 33 and also between the projection 2^ and the xibs j"/- inrthe .upper and lower halves22.a andiib.

The distance from the center of the driving hole of the lower half 21b to the ribs 33 and somewhat longer the radius of the flexible magnetic disk 2/ so that even if the flexible magnetic disk^/.is displaced within the cassette cover 22-by the looseness of the center core disk^J in the driving hole2%, the peripheral edge portion of the flexible magnetic disk Xf does not abut the ribs &3 . and .

In the upper and lower halves 22a and S^b of the cassette cover and the non-woven fabric if" , there are J4 2110 54 respectively formed opening j/ , 3^ and of the same shape extending in a radial direction of the flexible magnetic disk 2// the opening! ?/, and «?(P being overlapped in opposed relation.. And as will be described 5 later, a magnetic head is inserted from the opening &y formed in the lower half22b through the opening formed in the lower non-woven fabric while a head pressing pad is inserted from the opening 3/ formed in the upper half22a through the opening formed in the TO upper non-woven fabric 3jr. In Fig.^ , the reference numerals 3^ a and b are positioning projections for mutual engagement when assembling the tipper and lower halves 2ia and lib.

As shown in Figs.3 and 6,. there is formed a recess 15 on each of the outer surfaces of the upper and lower ha Ives 22 ei and 2^b in the respective portions where there are formed the pad insertion opening and the head insertion opening , and in the recess there is mounted a. shutter £/. having a tJ—shaped cross-section made 20 from aluminum, stainless steel, a synthetic resin, or the like so as to be slidable in a predetermined direction. • In the recess UO of the lower halfiib, as shown in Fig.^ , there is formed a rectilinear guide groove U-l. extending along a side edge portion of the cassette cover while 25 in relation to the guide groove there is formed in the shutter' V-/ , as shown'in Fig.j*., a pawl-like projection , for example in three places, formed by inwardly bending a part of the shutter by means of press or the like. The pawl-like projection ^ of the shutter UJ 30 is inserted in the guide groove (P- of the lower half22.b J5 2 1 1054 bo that the shutter <*/ is guided by the guide groove slidably in the direction of arrows A and B in Fig.<^ r The shutter sliding mechanism is not limited to what has just been mentioned. For examples, as shown in Fig. ^ , a part of the shutter ty-f may "be sujbected to half-blanking by means of press or. the like to form a projection C/Y a which projects inwardly of the shutter £/ , and the projection ■ In the .side edge portion of the lower half 22b where the guide groove is formed, as shown in Fig. 4 , there is formed a shutter mounting and demounting recess commnunication with the guide groove (fj. , for exarple in• three places. When the shutter is slided, for example, in the direction of arrow B in Fig. ^ to the position indicated with a dot-dash line, the recess and the pawl-like projection (ej of the shutter < In each of opposed plate portions <£/a and V/b of the shutter U-t there • is formed an opening having the substantially same shape as the pad and head insertion openings 3l and . By sliding the shutter U-j along the guide groove 9~2~, the pad and head insertion openings and S"7 can be opened or closed selectively.

I I in 2 1 10 54 r't * T In case the shutter $*/ is disposed in such a position as indicated with a solid line, in Fig.^ , the opening in the shutter £/ and the openings ;?/ and if in the cassette cover become overlapped with one another, that is, the openings and 3"/ are opened. On the other hand, in case the shutter is elided to the position shown with .a dot-dash line in Fig. b , the openings',^ and are covered "and closed with the shutter £/.

In the side portion of the cassette covert where the shutter W is mounted, there is formed a> "^cutout portion £3 as shown in Fig.^? and Fig. £ , and the cutout portion is opened or closed along with the above-described sliding movement of the shutter V/.

That is, when the opening in the shutter W,) . ~~ ~ yand the opening 38 of the fabric 3 openings «?& and in the cassette cover ££ overlap each other, the cutout portion S3 is opened, while when the openings 31,33 and. 38 are covered with the shutter 4-/, \_also j the cutcrut portion j(3 is^closed. Jtn .case the cutout portion &3 is opened, as will be described later, the \up to the right position of y cassette cover XL can be instalieSNsi* the recording and/or reproducing apparatus, and there can Le performed recoridng and reproducing operation. But, in case the cutout portion is closed by the shutter^/, as will be described later, disk cassette 26 can not be installed in the normal operating position on the apparatus and therefore misoperation is prevented. - Further in order to prevent the cassette cover-ii from being installed in an erroneous direction, there is formed a triangular cutout portion £2. at one ' predetermined corner iiu ju- of the 17 211054 cassette coverXi.

In this embodiment, moreover, there is provided an erroneous erase preventing mechanism at one corner of the cassette cover ^ bo that the information recorded on the flexible magnetic disk.2/ may not be erased by mistake. That is, as shown in -Fig. J and Fig.//, a channel-shaped cutout portion is provided at a predetermined corner of the lower half -^b of the cassette cover 22, and within the cutout portion an erroneous erase preventing detent is connected integrally with the lower half izt through a thin portion formed by a V-shaped groove . On the inner surface on the tip end side (free end side) of the detent there is integrally formed an abutment extending toward the upper plate22c oftthe upper half22a and the tip end of the abutment is in contact with the inner surface of the upper plate2^£. Accordingly, even when there is exerted an urging force in the direction of arrow c in Fig.nj _ the erroneous erase preventing detent is not separated from the lower half22J?. If it is desired to separate the detent from the lower half 22 b for the prevention of an erroneous erase, there may be applied a pivotal force in the -direction of arrow D in Fig. //to the tip end of the detent "whereby the thin portion ^ can be cut easily to remove the detent kv folding. ^he reason for such a construction is that in the thin cassette cover-21 it is restricted, in point of thickness, to push and fold off the detent I i IS 211054 inwardly. The construction as in this embodiment permits the detent ^ to be folded off surely and easily.

• At the two corner portions on the side of the opening of the lower ha If 22b and in positions outwardly deviated from the ribs 3ft, there are "formed a pair of positioning holes f~/ for positioning the cassette cover 2X when the disk cassette is installed onto the recording and/or reproducing apparatus. In this embodiment, moreover, auto loading cutout portions and having a semicircular section are formed in both side portions of the cassette cover^i. Within the cutout portions Sty and £$~ there are inserted a pair of supporting rods (not shown) of a predetermined moving mechanism for holding the cassette cover ,22., and moving the latter automatically to a predetermined position as necessary. Consequently, by utilizing the auto loading cutout portions J~¥- and it is made possible to constitute the apparatus so that there can be performed an .auto change of the disk cassette and an automatic cassette take—out operation at the time of quality inspection.

The following description is now provided with reference to Fig. /-i. to Fig. 2^ about the structure of the recording and/or reproducing apparatus onto which I r. 1 if ; 1 n" the disk cassetted is installed.

As shown in Fig. /J) to Fig. /$£> on a chassis &/ of a recording and/or reproducing apparatus (hereinafter referred simply to as the "apparatus") &0 there are mounted four cassette receiving pins , £L for receiving the disk cassette-2^. Among these pins, •' on the upper ends of the two pins and &V- there are integrally formed cassette positioning projections i7 and $ respectively adapted to fit in the/ pair of positioning 39 2 holes i"/ formed in the cassette coverJi. The cassett receiving pins , l Onto the chassis If there are fixed a pair of L-shaped supporting members and , to which a cassette presser member is attached by pivots 7-? and 7^ respectively.' The cassette presser member fx. has a plate body ^2.a, four cassette pressing pins ?S~, Jb , 77 and are mounted on the- lower surface of the plate body That is, as shown in Fig. ./jr to Fig./^ < these pins to Jfr are slidably supported in the vertical direction by a sleeve 7f provided in the plate body Jl a and at the same time are normally biased resiliently downwards by a compression coiled spring .?/ interposed .between the sleeve and a spring shoe«f^. Accordingly, -the disk cassette i/ is pressed for holding towards the cassette receiving pins 13 , &¥■ , and &£> -by the cassette pressing pins 7Sr, yl; 77 and 7^..

In this embodiment, as is apparent from Fig. ftf. , the disk cassette l£> is received at its four corners by the cassette receiving pins 13 , and £6. On the other hand, the positions wherein the cassette pressing pins 7-i~» / 77 t*16 cassette presser member hold down the disk cassette are each offset by a predetermined length from the positions of the pins i~i , and toward the central side of the disk cassette-^. That is, the cassette pressing pins pS~-aaid 77 disposed nearly on a line joining the cassette receiving pins £3 and /.£" and are disposed, between these pins l>3 and /iT, and are so constructed as to be in corresponding relation to the ribs $3 and of the disk cassette.)/. The cassette pressing pins 7^ and 7^ and t I 2 1 1054 the cassette receiving pins and il are disposed also in the same relation as above.

On the chassis L/ there also is mounted a driving mechanism for rotating the flexible magnetic diski/ in the disk cassette-2/. At a nearly central position of the portion surrounded with the cassette receiving pins ^3 , iH- , (Jr and Ij, , there is mounted a flat-type brushless motor 2S for rotating the flexible magnetic disk i/ in the disk cassette 26. As shown in Fig./J* , on the upper surface of a rotor a of the motor , a spacer ^ in the form of a partially cutout ring-like disk, a leaf spring member to which a spring-biased driving pin OLST for positioning (centering) the flexible magnetic disk 2jj ^in the cassette cover 22, and a disk-like yoke fo having a ring-like recess formed in the upper surface thereof are tightened together with a pair of setscrews f/. The leaf spring member ^ is interposed .between- the spacer ^ and the yoke , and the spacer the leaf spring member && and the yoke fo are further tightened together with a setscrew J2 , so that these components are rotated together with a motor shaft Pj.b of the motor a * In a nearly central part of the leaf spring member H, as shown in Fig. / being supported from both sides by the pair of arm portions And the driving pin I 21 211054 ' < < 1 is fixed to the pin mounting portion f(> . The spring-biased driving pin as shown in Fig. / f to Fig. xf , is constituted of a stem portion having a nearly centrally located flange a, a bearing portion fitted and fixed over the upper end portion of the stem portion J8., and a cylindrical portion /o/ mounted rotatably with respect to the stem portion by means of a ball bearing fov disposed between the bearing portion and the cylindrical portion (of. The stem portion extends throuah the pin mounting portion , and onto the lower end portion of that extending portion of the stem portion there is fixed a cylindrical mounting member /c2. By the flange a of the stem portion fP and the mounting member fc2, .the-pin mounting portion of the leaf spring member fi is held in place whereby the spring-biased driving pin S£ is secured to the pin mounting portion And the pin is disposed in such a state that the cylindrical portion /of of .the pin , the top portion c engages the inner surface of the upper plateiic to correct the inward warp of the latter.

On the other hand, in the recess of the yoke Jo four pairs of magnets /p^are fixed with an adhesive or the like at nearly egual intervals in the circumferential direction. On the upper surfaces of inner and outer flanges Jpa, /ta*b of the yoke Jt? there are respectively sticked lubricant" sheets (ft, /oi consisting of a Teflon sheet or the like incorporating carbon. As shown in Fig. to Fig. 2-^/, the upper surf aces .:of the lubricant sheets /£ .

In Fig. fX and Fig./}, the reference numeral- /oJ is a motor cover having an opening /o7a formed in the upper surface thereof. Within the opening A"/a the yoke fc is rotatably disposed within the opening and the lubricant sheets (o£ -and sticked on the yoke fo is projecting upwards from the upper surface of the motor cover/Of.

Next, an explanation will be given hereinunder ■ about a head moving unit in the apparatus l>0 .

The head moving unit includes a head support HQ 23 i / 2 1 10 54 onto which J a magnetic head fo? is secured on a mounting plate toj, and a feed screw 1(2 which is driven by a step motor/// about the axis thereof. As shown in Fig./i to Fig. /^/ the step motor /II is screwed to a vertical piece //J of the chassis if, and a motor shaft///a of the step motor /// is directly connected to the feed screw 112.. The other end of the feed screw f/1 is rotatably attached to a cutup piece//7 of the chassis (,} , and the feed screw /12. is disposed horizontally with respect to the chassis if .

In this embodiment, the head support I/O is so constructed as to be movable along the axis of the feed screw 111. That is, a pair of guide shaft mounting portions Iff r //J" are provided on the chassis .if., and both end portions of a guide shaft Hi having a circular section are fixed to the mounting portions //{£and//.£\ The guide shaft (tl, , which is disposed in parallel with the feed screw //X, extends through the head .support 110 .and in this state it is borne by a sleeve US' -fixed to the head support HQ. .'Consegutently, the head support JtO is slidable while being guided by the guide shaft f/t in the direction of arrows S and T in Fig. 12. and Fig.-i^- With the head support//", as shown in Fig. and Fig.-2-2, there is integrally formed a-pair of needle-like member mounting portions fXo which are opposed' to each other in spaced relation. The feed screw extends-through an opening /i/ formed in the vertical piece /!} of the -head support HO, and is disposed between the pair of needle-like mounting portions /2-0 . In the upper surfaces of the pair of mounting portions /Xo there are formed V—shaped grooves /22.'.a and /22-'.b respectively, the V-shaped grooves /ila and /XJLh I 24 having an inclination corresponding to the pitch angle of the threaded portion of the feed screw /IX in the direction orthogonal to the axis of the feed screw fix and extending on the same straight line. And a needle-like member fXtf. is spanned between the pair of mounting portions fXo with its end portions inserted in the V-shaped grooves (XI a and /■21b. Furthermore, as shown in Fig.2^, it is inserted without looseness, between and along adjacent threads (i.e. root) of the feed screw //X. Above the needle-like member ll*f- there is disposed a keep plate />£" which is fixed onto the upper surfaces of the mounting portions /Xo with a pair of setscrews /l/p whereby the needle-like member /s secured to the mounting portions /Xo in the aforesaid state of arrangement. ' Furthermore, as shown in Fig.if", a leaf spring /xj is fixed to the lower surface of one mounting portion fio "with the setscrew [X& , and by virtue of a resilient restoring force of the free end of the leaf spring the -feed screw IJ2 is normally urged to the needle-like member /Xif. and the keep plate /^£". Consequently, the needlelike member /*-(£ and the threaded portion of the feed screw //2 never become disengaged from each other, and the needlelike member /X On the head support HO, as shown in Fig. /iand Fig.2£ When the disk cassette xL is not installed on the apparatus lo , the head support tto is urged in the direction of arrow I in Fig. IX against the urging force of the compression coiled spring /JJ by vsuch as plunger solenoid j means of a predetermined urging mechanism (not shown), so that the pad /3-$. is spaced from the magnetic head/'j*. That is, the state of the apparatus &o shown in Fig. /X. is the vgr.inot . in operation J 15 . state in the case that the disk cassette xi is not installed. \or in operation J When the disk cassette Xl has been installed', the head support /'to is pivotally moved in the direction of arrow H by virtue of the urging force of the compression coiled spring /J3 . As a result, as shown in Fig-iJ^, the magnetic diski./ exposed 20 to the openings anfl in the cassette cover xx is held between the pad fi} and the raagnetic head (<$.

Referring now to Fig.-2?, a disk /if" made of a synthetic resin or the like is coaxially fixed onto the other end of the motor shaft ///£ of the step motor ///, "and 25 a reflector f){> is mounted on a part of the peripheral surface of the disk On the other hand, a detector /3? consist ing of a light emitting element and a light receiving element (photo-sensor) is disposed in opposed relation to the outer peripheral surface of the disk /)£ ■ & rotational position 30 of .the motor shaft ///.a of the step motor /// is detected I 2G 2 1 1 0 54 by the function of the detector /ij and the reflector /i/.

And a detection mechanism 13.7.a for -detecting a movement position of the head support t(o with respect to the feed screw //2. is mounted near both ends of the feed screw //2. On the basis of detection signals from this Vj37a^ detection mechanism and the detector {3J, there are decided rotation start and stop positions of the motor shaft///a as will be described later. As a result, the magnetic head (C% can be moved by only an amount of movement required for the magnetic disk 2/ to be recorded or reproduced by the magnetic head (02 (namely within a predetermined range of movement) . The reference numeral /3P in Fig.7.2. is an optical pulse generator for detecting a rotational phase of the flat-type brushless .motor .' On the cassette receiving pin , as shown in Fig./2 and Fig. .2^, there is mounted an erroneous erase preventing detent detecting member / When the detector portion of the detecting member fV-P has been forced down by the erroneous erase preventing detent of the cassette cover.22, the other end portion of the detecting member lU-0 gets in between the light emitting and receiving elements against the urging force of the compression coiled spring /y.f , whereby the recording operation y is prevented. v is . performed in the above case. And otherwise the recording operation1' In this embodiment, in order to prevent an erroneous installation (loading) of the disk cassette onto the apparatus there.are formed .erroneous installation preventing projection tf side in 1 5 opposed relation to the channel—shaped cutput portion and the triangular cutout portion & bgth formed in the disk cassetted, respectively.

Next, the following description is now provided about the operation of the apparatus £& having the above 20 construction.

First, the shutter of the disk cassette to be installed onto the apparatus £,& is sliaed in the direction of arrow A in Fig.^ until the openings and of the disk cassette and the opening of the shutter • are 25 overlapped with each other, whereby the openings H and are opened and at the same time the channel—shaped cutout portion S3 of the disk cassette is opened. Thereafter, the disk cassette is installed onto the apparatus Ct> by means of a cassette loading mechanism not shown. In this 30 case, as shown in Fig./^Z, the erroneous installation preventing 23 projection and /V~7 of the chassis £/ can get in the channel-shaped cutout portion J3 and the triangular cutout portion £2 of the disk cassetted, respectivelyso that the V_be ; •cassette oover 22 can .• disposed in the normal loading position, and the disk cassette is placed on the cassette receiving pins and by means of the cassette loading mechanism. In this, case, the projections &7and of the cassette receiving pins and tv- are respectively fitted into the positioning holes and £"2 formed in the cassette cover 22, whereby the positioning of the disk cassette is effectdd in its planar direction, i.e. longitudinal and transverse presses, direction. At the same time, the cassette pressure member Jz. moves pivotally about the.pivots and JV- in interlock with the cassette loading mechanisr;, thus allowing the pins ?S~, iL r 77 and 78" of the cassette presser member 7-^ to force down the disk cassette elastically downwards.by virtue of the urging force of the compression coiled springs 8i.. Accordingly, the disk cassette is held resiliently between the pins ^3 , £<£, 6S~ and IL and the pins 7f~, 7^ «■ and pS* of the presser member whereby the positioning of the disk cassette ^ in the direction of the height is effected.

When installing the disk cassetted, in case the cutout portion £3 is covered with the shutter w. or in case the triangular cutout portion $2- is not disposed in the normal position (that is, in case the loading direction of the .disk cassette .is not correct), since corner portions of the shutter and the disk cassette V will strike against the projections and /<# , the disk cassette is not disposed in the foregoing normal loading position. Consequently, the foregoing loading operation is not performed and hence I 29 2 110 54 i > recording and reproducing operation are not carried out. It is therefore not possible at all that the magnetic head will be damaged upon its abutment with the shutter which covers the opening of the disk cassette.^.

On the other hand, the portion of the disk cassette lL where the openings and 57 are formed is inserted between the magnetic head {(>$ and the pad (7$ . In interlock with the loading operation of the disk cassette 2l by means of the loading mechanism not shown, the pad supporting member /if is pivotally moved in the direction of arrow H in Fig. f2-and Fig.2-^-by virtue of the urging force of the compression coiled spring • thus resulting in that a part of the flexible .magnetic disk exposed through the opening fcf~.in the shutter In this case if the erroneous erase preventing detent of the disk cassette .3^ has not been folded off, the detector portion ,/(/3 of the detecting member IfO , as indicated with a dot-dash line in Fig..l/, is forced down against the urging force of the compression coiled spring /yt/ by the detent U-J, thereby allowing the gap between the light emitting and receiving elements of the detector (Ulf. to be interrupted. As a result, the apparatus &0 is ready to perform recording and reproducing operation on the basis of a predetermined signal from the detector /*+({-. On the other band, in case the detent has been folded off, the tip end of the detector portion of the detecting member /fco can get into the cutout portion ^ of the cassette coverIX. .Therefore, the detecting member [(±0 is left to be disposed in the upper position by t I 2 1 10 54 r • virtue of the compression coiled spring /V-/ , so that the gap between the light emitting and receiving elements of the detector /W is not interrupted and hence the apparatus £,o is maintained in a state not performing a reproducing operation on the basis of a predetermined signal from the detector Along with such a loading operation of the disk cassette, the motor shaft ^3b is inserted in the center aperture If of the center core disk 23 fitted in the driving hole of the lower half22b of the disk cassette^. In this case, if the upper plate22c of the loaded disk cassette is warped (bent) toward the lower plate22d as indicated with a dot-dash line in Fig. the hemispherical top }c of the motor shaft <£?b comes into contact with the nearly central part of the inner surface of the upper plate 21c". Consequently, a force in the direction of arrows J and \K in Fig .2j is exerted on the upper plate2Lc'by the pins ?J~« , and ^ . As a .result, when the loading of the disk cassette il is over, the • deformation (inward warp) of the upper plate ii.a is already corrected and the upper plate 22_a is flat as indicated with a solid line in Fig.2^.

On the other hand, when the disk cassette has been installed the pressing position of the pins ")£ , 77 and 7f* of the presser member 72- are on the diagonal lines of the pins £3 , CV-., 6f~ and £6 as previously noted and they are the positions corresponding to the xibs 3$ and ?$£ of the disk cassette2/. Therefore, if the lower plateild of the disk cassette 2.1 to be installed is deformed inwards, namely toward the upper plateas indicated with a dot-dash line in Fig.27/ the lower plate^ld undergoes a force in the 1 31 2 110 54 t j direction of arrows L and M through the ribs $3 of the upper halfiia and the ribs of the lower half 22,h, thus resulting in that the deformation of the lower plate22d is corrected and the lower plate22d becomes flat as indicated with a solid line in Fig.-*^.

In this embodiment, as set forth above, even if the upper and lower plates^c and-^d both are .warped (deformed) inwards, this warp (deformation) can be corrected to a satisfactory extent. As a result, the space within the cassette cover when installed can always be maintained constant, there is no fear of an obstacle to the rotation of the .magnetic disk Z/, and the flexible magnetic diski/ can be rotated with a relatively small driving torque.

Along.with the aforesaid installation (loading) of the disk cassette 4. the center core diskis attracted by the magnets fo(f of the yoke fv and is disposed on the lubricant sheets />& and /<>£> sticked respectively on the upper surfaces ^ of the flanges fo a and fbh of the yoke fP.. In this case, if the position of the driving- and positioning aperture i^Tin the center core disk 23 that of the spring-biased pin are shifted from each other, the pin Jfcf" is forced down by the center core disk by virtue of the attractive force exerted between the center core disk.i? and the magnets /of. As a result, as shown with a solid line in Fig.iO, the pin is forced dcwn against the resilient restoring force of the leaf spring , particularly the arm portion In such a state, when the apparatus £o is changed to the recording or reproducing mode and the motor shaft b cf the motor is rotated, the pin fiT rotates together with the leaf spring an(^ t'ie y°ke *jo with respect to the center core I I «- 32 2 disk .23. At this time the flexible magnetic disk is held between the magnetic head (°% and the pad as previously noted whereby load torque is exerted on the magnetic diskJS/. Consequently, even if a frictional force is exerted between the lubricant sheets /"t and fob sticked on the yoke Jo and the center core disk-23/ -and between the latter and the pin , the center core disk is not rotated and the pin moves round relatively to the' stationary center core disk Thereafter, when the driving and positioning aperture .if" in the center core disk is reached as indicated with a dot-dash line in Fig.^?-, the cylindrical portion .(°f of the pin gets in the aperture if~by virtue of the resilient Vesotring'' force of the leaf spring . Then, as tne motor shaft ^3 b rotates in the direction TDf arrow N, the pin is further moved round and the cylindrical portion (of of the pin comes into engagement first with a positioning edge ja located farther from the motor shaft $.b out of a pair of longer edges of the apertmr alt. Then the pin is further moved round and comes irrto engagement with a driving edgeifb of the aperture ^"while the cylindrical portion /eJ of the pin is rotated with the ball bearing ftto since a holding force induced by the magnetic head fof ana the pad and an inertia force caused by the difference in revolution between the yoke fo and the center core disk are exerted as a load torque on the magnetic disk and.the center core disk^J. In this case, as previously noted, since the distance SI shown in Fig.{f is set slightly longer than the distance S2 shown in Fig. the pin is brought into an inclined state by a torsional deformation of the ana portion ft of the leaf spring as illustrated in Fig.*/. 33 / 4 3 X TO 2 1 1054 As a result, the axis of the pin now has a slight inclination with respect to the vertical direction in Fig.-V, so that on the center core disk ^3 there normally is exerted ar^irging force in the direction of arrow P in Fig. xf and Fig. through the cylindrical portion /»/of the pin &Tby virtue of the resilient restoring force of the arm portion of the leaf spring .

-Although the load torque applied to the flexible magnetic disk i-j by the magnetic head and the pad is small, the provision in this embodiment of the ball bearing (a-Q between the stem portion and the cylindrical portion {*( allows the pin to be sure to move to the predetermined position indicated with a solid line in Fig. ■even if the forming accuracy of the insertion apertures J-^and 2^" in the center core disk is not so high.

As the center core disk is moved in the direction of arrow P, two sides l^a andj^b of a V-shaped corner located farther from the driving and positioning aperture .l^out of the four sides of the motor shaft insertion aperture 2}f- are brought into pressure contact at two points with the motor shaft and the center core disk.j£ is positioned.

Accordingly, the center of the flexible magnetic disk xf ! . } sticked on the center core disk .23 is disposed nearly on the ! axis of the motor shaft J*3 b- this state, as the motor L shaft $ b rotates and the pin is moved round in the i direction of arrow N in Fig.^P", the cylindrical portion /of j of the pin pushes the driving edge ifb of the aperture \ f it so that the center core disk .23 and hence the magnetic disk i/is rotated in the direction of arrow N. In this case, since the flexible magnetic disk 3-j is disposed concentrically 34 2 1 10 54 i < with the motor shaft fob as previously noted, it is rotated in an almost centered state.

Next, an explanation is here given about the operation of the head moving mechanism. First, when the apparatus is changed, for example, to the reproducing mode in a loaded state of the disk cassette in the manner as set forth hereinbefore, the flexible magnetic disk x/ rotates in the previously described manner. Along with this rotation, a recorded information is read-out by the magnetic head fof which is in sliding contact wiht the recording surface of the flexible magnetic diskJt/, and a . '. synchronizing signal contained in the read-out information is supplied to a step motor driving circuit (not shown).

Every time such , a .. ... - synchronizing signal is supplied, a predetermined driving current is provided from the above driving circuit to the step motor /// whereby the motor shaft Q ///a is rotated in the direction of arrowW in Fig. /2-and Fig-i-V^ in steps by a predetermined rotational angle (e.g. 15 degrees). Along with this rotation of the motor shaft ///a, the needlelike member inserted without looseness between adjacent threads of the feed screw //J. is moved in the direction arrow S by the feed screw //i. Thereby the head support ft&, together with the needle-like member/2y., is guided by the guide shaft ffb and moves stepwise to the next circular recording track intermittently, namely at every rotation of flexible magnetic disk ij, in the direction of arrow S. Consequently, the magnetic head (o$ and the pad supporting member tl-J both mounted on the head support HO slide integrally with each other and with the flexible magnetic disk 2{held therebetween, and move intermittently in the longitudinal direction I I . 2 110 54 r j . . within the head and pad insertion openings H and 3/ in the disk cassette, namely along a radial direction of the flexible magnetic disk-V- •; In this embodiment, as the pitch of the feed screw //I is relatively small and the" step motor/// has a relatively large rotational angle (e.g. about /i" degrees) per one step, even if the recording track pitch on the • flexible magnetic disk 2-f is small, it is possible to effect positioning of the magnetic head fofr with high accuracy with respect to the recording track to be reproduced. This is because even if step motors have the same mechanical accuracy in a single step rotation, the ratio of this mechanical accuracy to the one step rotational angle is smaller, in a step motor having a wider rotational angle, and therefore the magnetic head can be moved with high accuracy.

During the above movement, the feed screw //JL undergoes a downward force in Fig. and Fig. through the needle-like member But since an urging force toward the needle-like member /Uf. is excerted at all times on the feed screw //Z by means of the leaf spring fxj , the threads of the feed screw /Ai and the needle-like member /Zy. will never become disengaged.

In this may, the magnetic head /o^in sliding contact with the flexible magnetic disk 2/ moves stepwise and radially from the outer peripheral side toward the center of the magnetic disk if at every rotation of the motor shaft b, namely every time there is fed a synchronizing signal recorded on each circular recording track. When the head support Ho has been moved to a predetermined position and I 2 the magnetic head ($ has reached near the inside terminal edge portion of the magnetic surface of the flexible magnetic disk-2/, the position of the head support //P is detected by a detection mechanism 137a. Then, when the detector and the reflector L have become opposed to each other along with the rotation of the motor shaft ///a of the step motor !U, the rotation of the motor shaft///a in the direction of arrow N is stopped on the basis of detection 1137a ) signals from the above detection mechanisn? and the detector 10 l&J . Conversely, in case the feed screw //2 has been rotated in the direciton of arrow R in Fig. /X. and Fig.by means of the step motor ///, the magnetic head (°S is moved from the radially central side of the flexible magnetic disk i/ toward the outer peripheral side (in the direction of arrow T in 15 Fig. /2- and Fig.i}'-) . And when it has reached the outside terminal edge portion of the magnetic surface, the rotation of the motor shaft///a in the direction opposite to the previous arrow N direction is stopped.

Along with the above, operation the information 20 recorded on the recording^surface of the flexible magnetic disk X]is reproduced. Also in the recording operation, the same operation is performed as.set forth hereinbefore. - to be continued. - \ 37 According to the flexible magnetic disk cassette 26 and the recording and/or reproducing apparatus 60 each constituted as above, the spring-biased driving pin 85 pushes against the positioning edge 25a of the driving and positioning aperture 25 in the center core disk 23 to urge and bias the center core disk 23 radially outwards (in the direction of P in Fig. 28). Thereby, the motor shaft 83b comes into pressure contact with the two sides 24;a and 24b of a V-shaped corner of the center aperture 24 in the center core disk 23 to effect positioning (i.e. centering) of the center core disk 23 and hence of the magnetic disk 21, so that the motor shaft 83b and the center^core disk 23 are always brought into a constant positional..relationship when installing the magnetic disk 21. Accordingly, even if the positional accuracy of the insertion apeture 2 4 is poor, each center core disk 23 comes to have an intrinsic eccentricity. Therefore, if only the diameter of the motor shaft 83b.is finished with high accuracy, each center core disk 23 can be positioned at the same eccentricity every time the disk cassette is installed. As a result, tracking error can be ■largely suppressed since the magnetic disk 21 can be centered in just the same position at the time of recording and reproducing operation. For example, if the diameter of the motor shaft 83b is finished with an accuracy of ± 0.002 mm, tracking error is - suppressed also within the range of ± 0.002 mm. As a result, it becomes possible to perform a high density recording and reproducing operation.

In a conventional disk cassette, an index hole is formed in the upper plate of the cassette cover and a detector is disposed in opposed relation to the index hole » to detect a rotational position of the magnetic disk 21. On the other hand, in this embodiment of the present invention, the positional relation (rotational phase) between the motor shaft 83b and the magnetic disk 21 is always a one-to-one relation even when .the magnetic disk 21 is installed again. Consequently, if there is provided a pulse generator or the like for detecting a rotational position of the motor shaft 83b, it becomes unnecessary to form such an index hole as in the conventional disk cassette, and hence the aforesaid detector becomes unnecessary. In this embodiment, moreover, the installation of the magnetic disk 21 is made not by chucking the magnetic disk from above and below the cassette cover as in the prior art, but by an attractive ^ fixation of the center core disk 23 onto the yoke 90 on the'.lower half 22b side of the cassette cover 22, so that it becomes possible to constitute the flat-type apparatus 60. And even in the case of a relatively small-sized cassette cover, it becomes possible to affix a relatively large label to its surface.

Furthermore, since the magnetic disk 21 and the center core disk 23 are rotated by a rotational force of the pin 85, the magnetic attractive force of the magnets 104 may be relatively weak, and consequently there is no fear of recorded signals on the magnetic disk 21 being erased by this magnetic flux.

Although the illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiments, ''and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope and spirit of the invention as defined in the appended claims.

For example, the shape and position of the apertures 24 and 25 in the center core disk 23 may be changed; for example, for effective transmission of the rotational torque of the center core disk 23 by the motor shaft 83b and the pin 85, the center aperture 24 (motor shaft insertion aperture) in the center core disk 23 may be formed in a position shown in Fig. 29 slightly rotated in the rotational direction .(in .the direction shown by the arrow N) :of :±he..m<£itor shaft 83b from the position shown in Fig. 28. As shown in Fig. 30, moreover, the positioning edge 25a of the driving and positioning aperture 25 may be inclined and the driving pin 85 along with its pivotal movement, may be brought into the position shown while allowing it to abut, the inclined positioning edge 25a. In this case, the pin 85 is inclined more largely than that shown in Fig. 21 by the elasticity of the arm portion 95 of the leaf spring member 86, so that the center core disk 23 is biased in the direction of arrow P with a stronger urging force (elastic force).

In this embodiment the center core disk 23 is urged radially outwards (in the direction of arrow P) by the pin 85. But, in contrast therewith, the center core disk 23 may be urged radially inwards by the pin 85, as shown in Fig. 31. Furthermore, the shape of the apertures 24 and 25 are not limited to quadrilateral, they may be a polygon such as pentagon or hexagon.

In this embodiment, moreover, in order to have .'the pin 85 moved pivotally to the position capable of getting in the aperture 25, the required load torque is obtained by the holding force produced by the magnetic head 108 and the pad 128; however, the revolution of the motor 83 may be increased only during centering of the magnetic 5 disk 21 and the resulting inertia force may be utilized positively. It is also possible to bias the center core disk 23 without utilization of such a load torque. For example, as shown in Fig. 32, a leaf spring 150 having a weight 1S1 secured to its tip end portion and the pin 85 10 secured to its intermediate portion, may be pivotably mounted on a pivot 152 which is mounted on the back portion of the yoke 90 and in a position biased from its axis.

The pin 85 may be urged radially outwards (in the direction of arrow P) of the center core disk 23 and thereby the latter 15 may be biased. Furthermore, as shown in Fig. 33, the construction may be such that a positioning pin 15 3 provided on its tip end side with a tapered portion 15 3a is mounted on the rotor 83a of the motor 83 through a spring 154 the tapered portion 153a being capable of getting in the 20 aperture 25 formed in the center core disk 23, and the center core disk 23 is urged in the direction of arrow P by virtue of the urging force of the spring 154 which is transmitted to the positioning edge 25a of the apeture 25 via the tapered portion 15 3a. in this embodiment, moreover, the magnets 104 are used for fixing the center core disk 23 onto the yoke 90> but there may be used another mechanical mounting mechanism for the same purpose, and in this case it is not necessary to use a magnetic material as the center core disk 23.

The readers attention is drawn to our New Zealand Patent Specification Nos. 197970, 197971 and 210968.

V/ ■' ' .211.054'

Claims (5)

WHAT WE CLAIM IS:

1. A flexible magnetic disk cassette comprising: (a) a flexible magnetic disk; x. (b) irrelatively rigid central core for said disk, said core having a hollow central part and an : annular fringe part extending therefrom, said core being connected to said disk by said annular fringe part; and (c) a cover comprising an upper part and a lower part, said upper part covering one face of said disk and said lower part covering the other face of said disk, said upper part having a centrally located projection received in the hollow central part of said core and said lower part having an opening in which the hollow central part of said core is received, the construction being such that rotational drive to said disk can be effected by engaging said hollow central part with drive means engageable from the lower part side of said core and wherein radial displacement of said disk is inhibited by said central hollow part engaging with either or both, the side walls of the opening in said lower part, or said projection.

2. A flexible magnetic disk cassette as claimed in claim 1 wherein said core is of metal.

3. A flexible magnetic disk cassette as claimed in claim 1 or claim 2 wherein said core is made from sheet metal and has a generally top-hat longitudinal cross-sectional shape.

4. A flexible magnetic disk cassette as claimed in any one of the preceding claims wherein said centrally located projection of the upper part is an annular projection.

5. A flexible magnetic disk cassette substantially as herein described with reference to Figures 3 to 7 of the accompanying drawings. „ t . „ DATED THIS^ PAY OfOcfet^ A. J- FA?iK •& CON