Magnetic tape cassette drive system

A magnetic tape drive system for a video cassette recorder comprises a flip-over magnetic tape cassette having side-by-side reel hubs, each hub having a disc-shaped centering and drive member in the center of the hub with a central centering aperture and one or more drive apertures at some radial distance from the centering aperture, and a drive arrangement with drive spindles having a centering pin for the centering aperture in the reel hub, and at least one resiliently depressable drive pin which engages a drive aperture. To ensure correct positioning and drive of the spools and an excellent lace-up, and prevent undesired variations in the tensile stress in the magnetic tape and thus variations of the stretch of the magnetic tape, the reel hubs are resiliently urged onto stop surface which rotate with the drive spindles. The resilient urging devices and drive apertures are arranged to prevent disturbing forces on the reel hub.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a magnetic tape drive system for passing a thin 
flexible magnetic tape along a plurality of magnetic heads and comprising: 
(A) a "flip-over" reversible magnetic tape cassette, which is adapted to be 
supported on a magnetic tape cassette recording and/or playback apparatus 
(hereinafter called a cassette apparatus) in a first and in turned over or 
reversed second position, in either of these positions the magnetic tape 
being disposed to permit cooperation with the magnetic heads. Such a 
cassette has first and second adjacent reel hubs which are rotatable about 
parallel axes of rotation, each hub having a substantially tubular reel 
winding member which has an at least substantially cylindrical inner wall 
(as used herein "cylindrical" is to be understood as meaning circular 
cylindrical) and two annular end walls which are disposed in planes at 
some axial distance from each other perpendicular to the axis of rotation, 
as well as a disc-shaped centering and drive member midway between and 
parallel to the two end walls of the reel winding member and provided with 
parts which define a central centering aperture as well as at least one 
drive aperture at some radial distance from the centering aperture; first 
and second plane-parallel main walls which axially enclose the two reel 
hubs with play, each provided with a first aperture coaxial with the first 
reel hub and a second aperture coaxial with the second reel hub; and a 
length of magnetic tape having a first end connection to the first reel 
hub and having a second end connected to the second reel hub, so as to 
enable it to be wound back and forth between the reels, with a straight 
tape portion along the front of the magnetic tape cassette. 
(B) a cassette apparatus having a frame a drive arrangement comprising 
first and second drive spindles which are rotatable about parallel axes of 
rotation, each provided with a centering in with a free end adapted to 
cooperate with the centering apertures in the reel hubs of the magnetic 
tape cassette; each drive spindle having at least one drive pin with a 
free end, disposed at some radial distance from the centering pin, 
resiliently depressable in a direction parallel to the axis of rotation of 
the drive spindle, and adapted to cooperate with a drive aperture in the 
reel hubs of the magnetic tape cassettes during operation; and cassette 
supporting means connected to the frame for cooperation, in the cassette 
first or second position, with the first or the second main wall 
respectively and thus supporting the magnetic tape cassette on the drive 
arrangement in an operating position in which the two reel hubs cooperate 
with the centering pins and the drive pins of the two drive spindles. 
2. Description of the Prior Art 
Such a magnetic tape drive system is known from U.S. Pat. 3,027,110. In 
this magnetic tape drive system a plurality of drive apertures are formed 
in the disc-shaped centering and drive member of each reel hub at equal 
radial distances from the axis of rotation of the reel hub and at equal 
distances from each other. If two separate winding motors for the two reel 
hubs were used, the spindles of the winding motors could also be used as 
centering pins for centering the reel hubs. The height positions of the 
reels in the magnetic tape cassette are determined by the location of the 
cassette on the cassette supporting means. 
The known magnetic tape drive system is intended for recording and/or 
reproducing audio signals on magnetic tape. For video applications, where 
signals of substantially larger bandwidth than in audio applications 
should be recorded and reproduced, such a magnetic tape drive system is 
less suitable. In the currently used magnetic video tape recorders which 
have been designed for the consumer market the signals are written on the 
magnetic tape with the aid of rotary video heads as obliquely oriented 
elongate and closely adjoining tracks. The oblique tracks are 
approximately 18 to 23 microns wide at a length of approximately 100 mm, 
while in some magnetic tape recorders, employing two magnetic video heads 
with different azimuth alignments the tracks directly adjoin each other 
without intermediate spacing. In order to ensure that with such magnetic 
tape drive systems a video cassette which has been recorded on one 
specific video recorder can be played back on another video recorder 
without loss of quality, a high accuracy of the tape transport and the 
tape guidance is essential, so that variations in the stretch of the 
magnetic tape and thus variations in the tension in the magnetic tape are 
minimized. In addition, the one video recorder should be capable of 
reading the tracks which have been written on the magnetic tape by another 
video recorder, and time errors should also be avoided because of their 
adverse effect on the picture quality. In view of the stringent 
compatibility requirements thus imposed undefined frictional forces should 
not be exerted on the magnetic tape reels, while other sources of tape 
tension variations should be eliminated as far as possible. 
Conventional video recorders employ several servo systems so as to obtain 
an accurate tape transport speed and minimal tape tension variations. As 
an example, the speed of rotation of the capstan is automatically 
controlled by means of one servo system, while other servo systems drive 
the rotary magnetic heads, the magnetic head control and the drive 
spindles. As a result of the variations in tension which occur in the 
magnetic tape, frictional forces which act an the magnetic tape reels 
represent errors for the last-mentioned servo systems and also for the 
other servo systems. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a magnetic tape drive system 
which reduces friction forces on and uneven motion of the tape reels, and 
therefore is more suitable for use in video recorders. 
According to the invention, the drive arrangement includes resilient 
loading means for resiliently urging the reel hubs against axial 
positioning means on the drive spindles during operation; and that in the 
operating position the reel hubs, the reels wound thereon, and the loading 
means in contact with the hubs run entirely clear of the walls of the 
magnetic tape cassette. Thus variations in tension in the magnetic tape, 
which could result from a less satisfactory centering and alignment of the 
reels relative to the drive spindles, are avoided. 
In many magnetic video tape recorders the drive arrangement is provided 
with a cassette holder which is movable between an open and a closed 
position for inserting or removing the magnetic tape cassette when in the 
open position, and for keeping the magnetic tape cassette in the operating 
position when in the closed position. In a preferred embodiment of the 
invention of advantage for video cassette recorders provided with such a 
cassette holder the resilient loading means for resiliently urging the 
reel hubs against the reel hub positioning means during operation comprise 
first and second reel hub loaders, which are journalled with play in the 
cassette holder, which loaders are each provided with a centering portion 
for centering relative to the tubular reel winding member of a reel hub, 
and which furthermore comprise first and second pressure springs, which 
engage the reel hub loaders by a point contact at a central location 
opposite the centring portions. A first advantage of this embodiment is 
that minimal axial forces are exerted on the drive spindles, and tensile 
forces will never act on the drive spindle. A second advantage is that the 
loading means are rotation-symmetrical and consequently will not give rise 
to any unbalance of the reels, which is of special importance during rapid 
transport of the magnetic tape during fast forward or reversal winding. 
Speeds up to roughly 2,500 revolutions per minute may then occur. Such a 
speed corresponds to a tape speed of approximately 3 meters per second 
during fast winding. Other advantages are that the construction is simple 
and that removal of the magnetic tape cassette is not hampered by the 
drive spindles. 
In a further embodiment the cassette holder is provided with a partly open 
bottom which faces the cassette supporting means of the drive arrangement 
and a member with bearing apertures for the two reel hub loaders, which 
member faces away from the cassette supporting means, the reel hub loaders 
being rotatable and axially movable with play in the apertures in the 
bearing member and each reel hub loader having a stop collar for limiting 
the axial movement in the direction of said bottom, and the cassette 
holder having resilient means for urging an inserted cassette in the 
direction of the bottom. The distance between the reel hub loaders and the 
bottom of the cassette holder, the dimensions of the magnetic tape 
cassette and the reel hubs, as well as the dimensions of the cassette 
holder and the cassette supporting means on the drive arrangement are all 
adapted to each other in such a way that in the open position of the 
cassette holder a magnetic tape cassette is movable over the bottom of the 
cassette holder without touching the reel hub loaders, and that in the 
closed position of the cassette holder the magnetic tape cassette is 
supported by the cassette supporting means at such a distance from the 
bottom of the cassette holder that the reel hub loaders cooperate with the 
reel hubs so as to be freely movable in the apertures of the bearing 
member. In this embodiment the reel hub loaders do not hamper insertion of 
the magnetic tape cassette into the cassette holder. Furthermore, no 
separate aids are necessary for applying the reel hub loaders to the reel 
hubs, because this is effected automatically when the cassette holder is 
moved from its open to its closed position. 
According to another preferred embodiment the parts of the discshaped 
centering and drive members of the reel hubs which define the drive 
apertures have flat wall portions for cooperation with the drive pins of 
the drive spindles, which flat wall portions extend substantially in a 
radial direction relative to the axis of rotation of the reel hub, so as 
to prevent the drive pins from transmitting nontangentially directed 
forces to the reel hubs. In this embodiment only minimal play is required 
between a drive pin and the wall of a drive aperture, because tolerances 
in the radial position of the drive pin are taken up by the elongate shape 
of the drive aperture. Thus, the impact between a drive pin and the wall 
of the drive aperture when the movement of the reel is reversed or during 
starting or braking of the reel will be minimized, which is favorable for 
the life expectancy of the magnetic tape drive and for the accuracy of the 
drive. Another advantage is that the bearing arrangement of the drive 
spindle is prevented from being loaded unnecessarily by non-tangential 
forces, which obviously do not contribute to the torque to be exerted. 
In order to obtain a well-defined position of the magnetic tape reels 
relative to the drive spindles in yet another preferred embodiment each of 
the annular end walls of the reel hubs is provided with three axially 
extending projections which are disposed at equal radial distances from 
the axis of rotation of the relevant reel hub and equidistant from each 
other. Each of the stop means which rotate along with the drive spindles 
for cooperation with the annular end walls of the reel hubs has an annular 
stop surface which is disposed in a plane perpendicular to the axis of 
rotation of the relevant drive spindle, so that the reel hubs and the said 
stop means cooperate with each other by means of a three-point contact. As 
the reel hubs are generally manufactured from a thermoplastic material by 
an injection-molding process, the provision of the axial projections will 
present no practical technical problems. The stop means which rotate along 
with the drive spindles may comprise accurately machined faces of metal 
stop rings. 
Within the scope of the invention an embodiment is also possible which 
ensures an entirely play-free centering of the reel hub on the drive 
spindles. This embodiment the centering apertures of the reel hubs have a 
transverse dimension which is smaller than the transverse dimension of the 
centering pins of the drive arrangement, and the disc-shaped centering and 
drive members comprise portions which relative to the axis of rotation of 
the reel hub, define slots which extend radially and which terminate in 
the centering aperture, so as to enable the disc-shaped centering and 
drive member to be slid onto a centering pin of a drive spindle so as to 
be clamped thereon, the portions which are separated from each other by 
the slots being slightly bent. 
Furthermore, other embodiments are possible within the scope of the 
invention, which do not require the use of reel hub loaders which are 
connected to a cassette holder. For example be characterized the resilient 
loading means for resiliently urging the reel hubs against the reel hub 
positioning means during operation may comprise a plurality of pressure 
members, mounted on each drive spindle and movable to a limited extent 
between a first position and a second position nearer the axis of rotation 
of the relevant drive spindle, as well as resilient means for loading the 
pressure members towards their first position, and the inner wall of the 
tubular reel winding member of each reel hub maybe provided with an 
internal annular stop for the pressure members, the pressure members 
bearing on the annular stops of the reel hub during operation and the said 
resilient means exerting a force thereon, of which at least a component is 
directed towards the reel hub positioning means. To avoid abrupt pushing 
or pulling of the drive spindles during placement onto or removal of the 
magnetic tape cassette from the drive spindle the inner wall of each of 
the tubular reel winding members near each of the two end walls has a 
diameter which decreases gradually down to the annular stop for gradually 
moving the pressure members from their first position towards their second 
position until the annular stop is reached, when the magnetic tape 
cassette is placed onto the drive arrangement. Thus the required force 
increases uniformly. 
According to still a further embodiment of the invention, in which the 
resilient loading means for resiliently urging the reel hubs against the 
reel hub positioning means during operation are disposed at the location 
of the drive spindles but which comprise no movable parts, each of the 
reel hubs, near each of the end walls of the tubular reel winding member, 
is provided with an armature ring of a magnetizable material, and each of 
the drive spindles is provided with magnetic means for magnetically 
drawing a reel hub against the reel hub positioning means in conjunction 
with an armature ring. When the magnetic means for pulling the reel hubs 
against the reel hub positioning means in conjunction with the armature 
rings comprise electro-magnets, this embodiment even enables, by switching 
the electric current to the electro-magnets, placement and removal of the 
magnetic tape cassette without the exertion of axial forces on the drive 
spindles. Moreover, use can be made of an embodiment in which the magnetic 
means on the drive spindles comprise annular permanent magnets whose an 
outer wall has the shape of a truncated cone whose portion having the 
smallest diameter is directed towards the free end of the centering pin, 
and the armature rings have an inner wall with a conical shape 
corresponding to the shape of the outer wall of the permanent magnets on 
the drive spindles, an air gap of substantially uniform thickness being 
formed in the operating position between the outer wall of each permanent 
magnet and the inner wall of the armature ring which magnetically 
cooperates therewith. With this shape of the magnet and the armature ring, 
when putting on the magnetic tape cassette initially a large air gap is 
present between the permanent magnet and the armature ring of every reel 
hub, so that the centering of the reel hub on the centring pin of the 
drive spindle is not adversely affected by magnetic forces exerted on the 
reel hub during centering. The shape of the permanent magnet and the 
corresponding wall of the armature ring may be selected in such a way that 
an optimum force-path characteristic is obtained. During operation the 
permanent magnets on the drive spindles are surrounded by the armature 
rings of the reel hubs, so that magnetic stray fields can be shielded in a 
satisfactory manner. 
The invention will now be described in more detail with reference to the 
drawing which schematically shows some embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following description of the embodiments shown in the drawing, the 
various parts are designated by different reference numerals, that when 
two identical parts are used these bear the same reference numeral and are 
only distinguished by the addition of "a" or "b" when this is of 
importance for a correct understanding of the drawing. 
The video cassette 1 (FIGS. 1 to 4 as well as FIGS. 7 to 9) is a so-called 
flip-over or reversible magnetic tape cassette which is adapted to 
cooperate with rotary magnetic heads of a video recorder when supported on 
the apparatus in a first position or in a reversed (turned over) second 
position. The cassette is provided with first and second adjacently 
disposed reel hubs 3 which are rotatable about parallel axes of rotation 
2, each with a substantially tubular reel winding member 4 having an at 
least substantially cylindrical inner wall 5, a substantially cylindrical 
outer wall 6 and two annular end walls 7 which are disposed in planes 
spaced axially from each other perpendicular to the axis of rotation 2. A 
disc-shaped centering and drive member 8 is located midway between and 
parallel to the two end walls 7 of the reel winding member and is provided 
with parts which define a central centering aperture 9 and six drive 
apertures 10 at some radial distance from the centering aperture 9. To 
both sides of the reel hub 3 transparent flanges 11 are secured, so that 
the assembly comprising the reel hub 3 and the two flanges 11 constitute a 
spool 12. For attaching a magnetic tape to the reel hub the hub has a 
recess 13 on its circumference. The end of a magnetic tape is pressed into 
this recess and retained therein by means of a resilient clamping member, 
not shown. 
In the video cassette the two spools 12 are axially enclosed with play by 
two plane-parallel main walls 14 each having a first aperture 15a which is 
coaxial with the first reel hub 3a as well as a second aperture 15b which 
is coaxial with the second reel hub 3b. The main walls 14 are 
interconnected by said walls 16, a rear wall 17 and a partly open front 
wall 18 which is disposed at a front side opposite the rear wall 17. The 
cassette contains a length of magnetic tape 19, which is connected to the 
first reel hub 3a at a first end and to the second reel hub 3b at a second 
end, so as to enable it to be wound from the first reel hub 3a to a reel 
20b on the second reel hub 3b and back from the second reel hub 3b to a 
reel 20a on the first reel hub 3a. A straight tape portion passes along 
the front of the cassette. A slide 21 is movably guided on the cassette 
housing, which slide in its retracted position releases a guard 22, 
alowing this guard to be pivoted open in a first direction (see FIG. 3), 
or in a second direction (see FIG. 4). Although the cassette is 
reversible, the straight portion of the magnetic tape 19 at the front of 
the cassette is always accessible to elements of the video recorder from 
the same side, independently of the position of the cassette on the drive 
arrangement. The slide 21 is resiliently loaded towards the front by means 
of a pressure spring 23 which bears on a spring cup 24. On each side the 
cassette has an aperture 122, and an aperture 123 which is slightly 
elongated in a direction parallel to the connecting line between the 
centers of the two reel hubs 3. These apertures accept locating pins for a 
drive arrangement as is explained hereinafter. 
For further information about the video cassette shown in the drawing, 
reference is made to previous non-published Netherlands patent application 
No. 78 04 936 to which U.S. Pat. application Ser. No. 974,296, filed Dec. 
29, 1978 and assigned to the assignee of the instant application, 
corresponds, hereby incorporated by reference. 
The drive arrangement comprises a frame 25 and two drive spindles 27 which 
are rotatable about parallel axes of rotation 26, which spindles are each 
provided with a centering pin 28 having a conical free end 29 and which 
are each adapted to cooperate with a centering aperture 9 in a reel hub 3 
of the magnetic tape cassette 1. Each of the centering pins 28 is integral 
with a motor spindle 30 of an electric drive motor 31. 
At some radial distance from the centering pin 28, there is provided a 
drive pin 32 with a rounded free end 33 on each drive spindle 27, which 
drive pin is resiliently depressable in a direction parallel to the axis 
of rotation 26 of the drive spindle 27 against the force of a pressure 
spring 117. The drive pins are adapted to cooperate with a drive aperture 
10 in a reel hub 3 of the video cassette 1. 
For supporting the video cassette in its first position or in its second 
position there are provided cassette supporting means 34 and 35 on the 
frame 25, which means cooperate with a main wall 14 of an inserted 
cassette for thus supporting the cassette on the drive arrangement in an 
operating position, see FIG. 8, in which the two reel hubs 3 cooperate 
with the centering pins 28 and with the drive pins 32. The supporting 
means 34 and 35 comprise projections which are integral with the frame 25, 
metal locating pins 36 for the tape guide elements 40 being secured in the 
projections 35. They have a conical end 37 and engage with the recess 39 
of tape guide members 40 of the video cassette with cylindrical portions 
38 and 111. These tape guide members extend beyond the main walls 14 of 
the cassette, so that when the cassette is in its operating position the 
tape guide members 40 are positioned directly on the cassette supporting 
means 35. Thus it is ensured that the correct position of the tape guide 
members relative to the parts of the video recorder which cooperate with 
the magnetic tape is not affected by dimensional tolerances of the video 
cassette housing. The tape guide members have some radial and axial play 
in the main walls 14; the locating pins 36 do not serve for locating the 
cassette housing on the drive arrangement. For this purpose further 
locating pins 124 are provided on the frame 25, also see FIG. 10. 
For axially positioning the reel hub 3 each drive spindle 27 is provided 
with reel hub positioning means comprising stop means in the form of 
planar annular surface on stops 41 which rotate along with the drive 
spindle for cooperation with the annular end walls 7 of the reel hubs 3. 
During operation each of the reel hubs 3 is resiliently urged against a 
stop 41 by means of resilient loading means, to be discussed hereinafter, 
which comprise a leaf spring 42 as well as hub loader member 43. The reel 
hubs 3 are then supported at such a height in the cassette 1 that the 
spools 12 run completely clear of the walls of the video cassette. 
The video recorder is provided with a cassette holder 44 which is movable 
between an open position, see FIG. 7, and a closed position, see FIG. 8, 
for inserting or removing the video cassette 1 in an open position and for 
retaining the video cassette in the operating position in the closed 
position. The cassette holder comprises two side plates 45 which are 
spaced from each other and which are connected by a rear plate 46, in 
which a torsion leaf spring 47 is mounted with the aid of which the 
cassette holder is pivotably mounted on supports 48 of the frame 25. 
Furthermore, the cassette holder comprises a bottom plate 49 and a 
connecting member 50, which interconnects the two side plates 45. The 
resilient loading means for urging the reel hubs 3 against the stops 41 
during operation comprise reel hub loaders 43 which are journalled with 
play, in the connecting member 50 of the cassette holder 44. Each of the 
reel hub loaders is provided with a centering portion 51 for centering the 
reel hub loader relative to a tubular reel winding member of a reel hub 3. 
The reel hub loaders are each loaded by the pressure springs 42, which 
cooperate with the reel hub loaders 43 at a central location opposite the 
centering portions 51 substantially by a point contact, namely with a 
rounded projection 52, which in the operating position is disposed on the 
axis of rotation 26 of the drive spindle 27. 
On the side which faces away from the cassette supporting means 34 and 35 
the cassette holder 44 is provided with bearing members 53 which are 
connected to the connecting member 50, which bearing members take the form 
of bent metal strips which are connected to the connecting member 50. In 
the bearing members 53 apertures 54 are formed for the reel hub loaders 
43, which apertures have such a diameter that the reel hub loaders are 
rotatable and are axially movable with play in the apertures. Each reel 
hub loader is provided with a stop collar 55 for limiting the axial 
movement in the direction of the bottom 49 of the cassette holder. A 
cassette which is placed in the cassette holder is urged against the 
bottom 49 with the aid of levers 56, which are journalled on the side 
plates 45, and tension springs 57. For this purpose the levers 56 comprise 
a pin 58, which pins 58 pass through slots 59 of the side plates 45 and on 
which the springs 57 act. On its other side each lever is mounted on a 
bearing pin 112 and is retained on that pin by means of a retaining ring 
113. The distance between the reel hub loader 43 and the bottom 49, the 
dimensions of the magnetic tape cassette 1 and the reel hubs 3, the 
dimensions of the cassette holder 44 and the cassette supporting means 34 
and 35 are all adapted to each other in such a way that in the open 
position of the cassette holder, see FIG. 7, the video cassette is movable 
over the bottom 49 of the cassette holder without contacting the reel hub 
loaders, and that in the closed position, see FIG. 8, the video cassette 
is supported by the cassette supporting means 34 and 35 at such a distance 
from the bottom 49 of the cassette holder 44, that the reel hub loaders 43 
can cooperate with the reel hubs 3 so as to be freely movable in the 
apertures 54 of the bearing members 53. Thus no undesired frictional 
forces or torques which have an adverse effect on the uniformity of the 
tape transport and the tension in the magnetic tape are exerted on the 
spool 12 during operation. 
FIG. 5 shows that the drive apertures 10 in the reel hubs 3 are not round 
but have more or less an oval shape. In order to prevent that during 
operation the drive pins 32 of the drive spindles 29 transmit 
non-tangentially directed forces to the reel hubs 3 the drive apertures 10 
are locally bounded by flat wall portions 60, which extend substantially 
radially relative to the axis of rotation 2 of the reel hub. The more or 
less oval shape moreover serves to take up tolerances in the radial 
distance of a drive pin 33 relative to an axis of rotation 26 of a drive 
spindle, while requiring only minimal play between the drive pin and the 
flat walls. 
Each of the annular end walls 7 of the reel hubs 3 comprise three axially 
directed projections 61 which are disposed at equal radial distances from 
the axis of rotation 2 of the reel hub and at equal distances from each 
other. The annular stops 41 which rotate along with the drive spindles 27 
each have an annular stop surface 62 which is disposed in a plane 
perpendicular to the axis of rotation 26 of a drive spindle 27. Thus the 
reel hubs 3 and the stops 41 cooperate with each other by means of a 
three-point contact, in such a way that an unambiguously defined position 
of each spool on its stop is guaranteed. 
FIG. 9 shows the method of positioning the video cassette on the cassette 
supporting means 34 and 35. At the location of the cross-section X--X in 
FIG. 9 a locating pin 124, having a conical end 125, engages an aperture 
122 of the cassette, the cylindrical portion of the locating pin having a 
slight play in the aperture. A second locating pin 124 engages an aperture 
123 of the video cassette (see FIG. 4 and FIG. 9). 
FIG. 11 relates to a slightly different spool 114, the transverse dimension 
of the centering aperture 63 of the reel hub 64 having a diameter which is 
smaller than the diameter of the centering pins 28 of the drive means and 
a disc-shaped centering and drive member 65 being provided with slots 66 
which extend radially relative to the axis of rotation of the spool and 
which terminate at their inner ends in the centering aperture 63 and at 
their outer ends in respective transverse slots 67 on the side opposite 
the centering aperture 63. By means of these slots it is possible to clamp 
the disc-shaped centering and drive member 65 onto a centering pin 28 of a 
drive spindle, the portions which are separated from each other by the 
slots 66 and 67 being slightly bent. This enables excellent centering of 
the spool, because there is no play at all between the spool and the 
centering pins in the drive arrangement. Obviously, for arranging such a 
spool on a centering pin, a specific axial force is required, while 
removal of the spool also demands a certain axial force. 
This is also the case with two other embodiments, namely those in 
accordance with FIGS. 12 and 13. FIG. 12 illustrates the cooperation 
between a centering pin 115 and a reel hub 68, which only differs from the 
previously described reel hubs 3 in respect of details. The reel hub 68 
also has a centering aperture 69 as well as six drive apertures 70 in a 
disc-shaped centering and drive member 71. The tubular reel winding member 
72 has reel flanges 73 on both sides, one of which is shown in the 
drawing, partly in cross-section. On the cylindrical outer wall 74 of the 
reel winding member 72 a reel 75 is wound. A member 76 is clamped onto the 
centering pin 115 and forms a part of a drive spindle 116. A flange-shaped 
portion 77 of the member 76 comprises an annular stop surface 82 on its 
upper side, which surface is disposed in a plane perpendicular to the axis 
of rotation 79 of the centring pin 115. In this embodiment the resilient 
loading means for resiliently urging the reel hubs 68 against the stop 77 
during operation comprise a plurality of loading members in the form of 
balls 80, which are mounted on each drive spindle and which are movable to 
a limited extent between a first or outer position, and a second or inner 
position, nearer the axis of rotation 79. These members are loaded towards 
their outer position by pressure springs 81. The tubular reel winding 
member 72 of the reel hub 68 is provided with an internal annular stop 83 
for the balls 80 near its end walls 82. As is shown in FIG. 11 the balls 
80 bear on the annular stop 83 during operation. They exert on the annular 
stop 83 a force having a component which is directed towards the stop 77. 
The stop 83 has a conical shape, each ball 80 bearing on the conical 
surface at a point which is disposed below the ball center. 
Near the end walls 82 of the reel hub 68 the tubular reel winding member 72 
has a conical inner wall 84, whose diameter decreases down to the annular 
stop 83. This inner wall serves to move the balls 80 gradually from their 
outer to their inner position until the annular stop 83 is reached during 
positioning of the magnetic tape cassette on the drive arrangement. The 
inner wall 84 belongs to a metal ring 85 which forms part of the tubular 
reel winding member 72 of the reel hub 68. On the member 76 which belongs 
to the drive spindle 116 a cylindrical metal sleeve 86 is fitted which 
retains the balls 80. At the location of the balls 80 round apertures 87 
are formed in the sleeve which have a diameter which is slightly smaller 
than the largest diameter of the balls 80, so that the balls can project 
from the sleeve but cannot be pressed out of the aperture by the springs 
81. A drive pin 88 is secured to a ring 89 inside the member 76. A 
pressure spring 90 urges the ring 89 upwards and bears on a stop ring 91 
with its other end. As a result of this construction the drive pin 88 is 
resiliently depressable to a limited extent in an axial direction. 
In FIG. 13 the reel hub 92 is substantially identical to that of FIG. 11, 
except that instead of the metal ring 85 a differently shaped metal ring 
92 is employed. This ring functions as an armature ring and is made of a 
magnetizable material which cooperates with magnetic means in the form of 
a permanent magnet 94, which forms part of a drive spindle 95 and by means 
of which the metal armature ring 93 is drawn against a stop 96 which 
functions as reel hub positioning means. This stop forms part of an 
element 98 which is secured to a motor spindle 100, which functions as 
centering pin, with the aid of a screw 99. The permanent magnet 94 is 
glued onto a plastic support 101, which by means of screws, not shown, is 
connected to the stop 96. The member 98 is provided with a threaded 
portion 102 onto which a cap 103 is fitted. Underneath this cap a ring 104 
is located to which the drive spindle 105 is secured. A pressure spring 
106 urges the ring 104 upwards and is supported by plastic support 101. 
The permanent magnet 94 on the drive spindle 95 is annular and has an outer 
wall 107 in the form of a truncated cone, of which the part with the 
smallest diameter is situated nearer the free end 108 of the centering pin 
100. The armature ring 93 has an inner wall 109 with a conical shape which 
corresponds to that of the outer wall 107 of the permanent magnet 94 on 
the drive spindle 95. In the operating position, see FIG. 12, an air gap 
110 of substantially uniform thickness is formed between the outer wall 
107 of the permanent magnet 94 and the inner wall 109 of the armature ring 
93. On its surface 107 the permanent magnet is provided with a large 
number of alternate north poles and south poles, so that in the operating 
condition the magnetic field lines are correctly shielded by the armature 
ring 93, which ensures that no problems can arise as a result of undesired 
stray fields. Moreover, the cap 103 and the stop 96 also consist of a 
magnetizable metal.