Limited play tape cassette system

An assembly added to a conventional VHS cassette provides a wheel for counting the number of plays, or replays of segments of more than a predetermined length, and preventing further replay after the last authorized play by either releasing a spring biased arm to carry an erase head against the tape, or locking the cassette brakes in the engaged position once the cassette is removed form the tape deck.

BACKGROUND OF THE INVENTION 
This invention relates to a system for limiting the plays of tape 
cassettes, such as video cassettes, and more particularly to a system for 
counting the number of times the tape is played, or partially played, and 
to stop any further playing after a predetermined number of plays. 
Mechanisms have been proposed for counting the number of times a video 
cassette has been used or played, and displaying the count for the purpose 
of computing a rental charge. See U.S. Pat. Nos. 3,995,319, 4,475,222, 
4,575,778 and 4,586,101. A mechanism has also been proposed in U.S. Pat. 
No. 4,466,584, which will limit the total number of plays. The system in 
that patent uses an escapement to count the number of plays. A tape feeler 
assembly provides the escapement with the necessary cyclic motion as the 
tape is played and rewound. Once a predetermined number of plays have been 
counted, the mechanism locks to prevent further playing by providing a 
wheel locked to the escapement with an abutment. 
A major disadvantage of that escapement system is inherent in the nature of 
an escapement; the mass of the base to which tape feelers are connected 
may be caused to oscillate, and thus advance the count wheel, if the 
cassette is jarred. It is for that reason that escapements are generally 
used only in systems that are handled with care, such as a clock, or that 
are so installed as to not be subject to being jarred. Another 
disadvantage is that locking the escapement, or a wheel connected to it, 
will not prevent further play; it will simply increase the drag on the 
reels. Such drag, if sufficient to prevent normal speed of the tape, may 
cause damage to the playback mechanism. 
Advantages of an arrangement for counting and limiting the maximum number 
of times a video cassette may be played are that the rental charge of a 
video cassette may be based upon the number of times it is played, and the 
distributor of the rental video cassette may limit the number of times it 
is played to protect the proprietor of copyrighted material recorded on 
the tape. However, such an arrangement has many problems to be considered. 
If the mechanism is set to advance the count only at either extreme of 
play and rewind, the intent of the mechanism is easily defeated by 
avoiding the beginning and end during successive replays. To set it to 
advance at some intermediate point is not the solution either, for that 
prevents the viewer from enjoying a legitimate replay of a scene spanning 
that point. 
Another problem is concerned with how easily the system may be defeated, 
such as by inserting a probe into the cassette to release the lock 
mechanism, or resetting the counter, after which the cassette will replay 
at least one other time, or replay the entire predetermined number of the 
authorized times. 
OBJECTS AND SUMMARY OF THE INVENTION 
A major objective of this invention is to provide a means of counting whole 
and partial play-rewind cycles of a video cassette (or similar magnetic 
tape or optical film cartridge). Such a mechanism will allow limited 
viewing of copyrighted material contained in any selected portion of the 
tape. This overcomes the limitations of the prior art which is 
nonselective in registering counts for partial use, and cannot register 
for repeated plays of small segments between the ends of the tape. Preview 
and trailer information could still be viewed repeatedly without penalty 
by adjusting a span of uncounted play-rewind cycles at the beginning and 
end of the tape to encompass the length of previews and trailers recorded. 
Another major objective is to limit the number of times the cassette may be 
played, by erasing the tape or by securing locks of the reels after the 
last authorized play. Optical warning of last use and/or locked condition 
may be incorporated in the design. 
In accordance with the present invention, a reel follower arm between the 
tape reels of a cassette pivots back and forth through an angle greater 
than or equal to a small defined angle as the cassette tape is played and 
rewound. During the play mode, a clutch (friction or detent) couples the 
motion of the follower arm to a count wheel comprised of a ratchet wheel 
and pawl. The counting action starts as the count wheel begins to rotate. 
When it has rotated sufficiently for the count to have been advanced by 
one, a clutch stop prevents further rotation of the clutch and count 
wheel, the ratchet pawl engages the next tooth of the ratchet wheel, and 
the clutch allows the drive motion between the follower arm and count 
wheel to slip. On rewind, the motion of the follower arm is again engaged 
by the clutch but the ratchet pawl prevents the ratchet wheel from 
rotating in reverse. 
Hysteresis inherent in the follower arm manifests itself upon changing 
direction of rotation, and will permit a predetermined amount of rewind 
without arming the counter for uncounted replays of small segments 
anywhere along the length of the tape. The minimum length of an uncounted 
segment replay is controlled in part by the gap between the follower arm 
and the tape being wound on a reel when the direction of the tape is 
reversed. The greater the gap, the greater the hysteresis, and therefore 
the longer the segment that may be replayed without penalty. If a detent 
clutch is used, the clutch coupling will slip until the next detent notch 
is reached. By programming the spacing of the notches, it is possible to 
pre-define particular segments within which replay is permitted without 
penalty. 
In the case of a detent clutch, a reciprocating arm coupled to the reel 
follower arm by the detent clutch carries a driving pawl which advances 
the ratchet wheel by one tooth for each play motion of the reel follower 
arm through an angle equal to or greater than the angle defined by the 
clutch stops. The detent then rides over notches until the end of the 
tape. When the tape is rewound, the detent engages the first notch 
encountered and the follower arm drives the reciprocating arm to drag the 
driving pawl over one tooth of the ratchet wheel for the next count. 
Clutch stops again prevent the ratchet arm from rotating further, and the 
detent rides over notches until rewind is stopped and play is again 
started. The first notch encountered by the detent will then cause the 
reciprocating arm to rotate and advance the count. If the rewind is not 
sufficient for the detent to engage another notch, and thus drag the 
driving pawl over the next tooth, the count will not be advanced when play 
is resumed. In that manner, the last segment played, or any portion of it, 
may be replayed without penalty. However, since the segments are 
predetermined by the spacing between notches, the detent clutch embodiment 
of the invention is better suited to cassettes on which programs have been 
recorded that consist of defined segments corresponding to the spacing of 
the detent notches. 
A spring loaded magnet is released from the tape follower arm when the last 
authorized play is started so that, as the tape is played, it is erased. 
This severely restricts replay of a segment during the last authorized 
play to just so much of the tape as is between the playback head in the 
tape deck and the erase magnet. That length of tape will take care of 
normal stop and restart actions, during which there is some rewind, and 
also permit a short scene to be viewed again. During the last play, the 
ability to replay programmed time segments would be lost. 
A reel lock or magnet release mechanism is triggered by the ratchet pawl 
dropping into a notch on the ratchet wheel after the tooth of the last 
permitted replay count in the case of locking up the reels, or in the 
position of the last permitted replay count in the case of erasing during 
that last play. The motion of the ratchet pawl dropping into the notch is 
sufficient to lock the reel brakes in the engaged position, once the 
cassette is removed from the tape deck, or to pull a pin holding the 
spring loaded magnet in the follower arm. Once the magnet is released, 
tape passing over it on play or rewind will be erased. 
Other objects and advantages of the invention will become readily apparent 
to those skilled in the art from the following description and the 
accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to the drawings, FIG. 1 illustrates the top and bottom halves 10 
and 11 of a conventional VHS video cassette from which it may be seen that 
there is space in the top half 10 over tape guide walls in an area 12, 
once tape guide walls in the top half are removed as necessary to mount a 
ratchet counter as shown in FIG. 2. The ratchet counter is comprised of a 
ratchet wheel 20 pivoted on a pin 21 extending through the cassette wall 
of the top half of the exploded view in FIG. 2. 
Referring again to FIG. 1, the cassette holds a supply reel 14 and a takeup 
reel 15 shown in FIG. 1. A window 16 in the top half permits viewing the 
amount of tape on the supply reel, and a window 17 permits viewing the 
amount of tape on the takeup reel. The tape feeds out past a post 18 from 
the supply side, and past a post 19 into the takeup side during play. The 
roles of the reels are, of course, reversed during rewind. 
Referring now to FIG. 2, the ratchet wheel 20 carries a count disc 22 with 
numbers as shown. These numbers are visible through a small window 23 in 
the top half 10 of the cassette housing. This window, shown open, is 
intended to be closed, preferably by a magnifying lens. A Y-shaped 
reciprocating lever 24 is also pivoted on the pin 21. Mounted on one 
branch of the reciprocating lever 24 by a block 24a is a wire pawl 25 
which communicates rotary motion to the ratchet wheel 20. A block 24b is 
also provided on the second branch. Together blocks 24a and 24b assure 
that the reciprocating lever 24 is spaced away from the upper half of the 
cassette housing so as not to jam against the ratchet wheel 20. 
As the reciprocating lever 24 rotates counterclockwise (as viewed in FIG. 
2), the pawl 25 rides over the teeth of the ratchet wheel. It should be 
noted that the count disc 22 is slightly larger than the sprocket wheel 
20. Another thin disc 22a of the same diameter as the count disc 22 
cooperates with the count disc to provide a channel between the discs that 
holds the pawl 25 over the teeth of the ratchet wheel. 
As will be described more fully hereinafter, the pawl 25 rides over one 
tooth of the sprocket wheel during rewind. Mounted on the top half of the 
cassette is a stop pin 27. This pin is positioned between the branches of 
the reciprocating lever 24 to limit the angle through which it pivots. 
Once the lever 24 has been pivoted sufficiently for the ratchet 25 to 
advance over just one tooth of the ratchet wheel 20, the pin 27 stops the 
lever from pivoting further. Upon playing the tape, the reciprocating 
lever is pivoted clockwise (as viewed in FIG. 2). The pawl 25 then pushes 
on the tooth it has just passed over to advance the ratchet wheel by one 
count which places the next number on the disc 22 under the window 23. 
Thus, the ratchet wheel advances the count only during the initial part of 
a play, and it advances the count by only one during each play, although, 
as will be seen later, replay of limited segments of the tape are 
permitted without penalty, i.e., without advancing the count by one for 
each replay. 
Riding over the ratchet teeth is a pawl 30 pivoted on a pin 31. The pawl is 
shaped with a finger 30a which just fits a slot 20a cut in the ratchet 
wheel 20. A wishbone spring 32 anchored on a pin 33 is so connected to the 
ratchet pawl 30 as to bias it against the ratchet wheel. Once the ratchet 
wheel has advanced the count disc to the number of the last authorized 
play, the pawl finger 30a will move into the slot 20a in the ratchet 
wheel. The spring 32 is provided with a "near center" loading so that the 
spring force is a minimum until the end secured to the pawl 30 begins to 
move. The spring force increases as the finger 30a moves into the slot 20a 
for positive latching. While the pawl 30 is thus rotating clockwise (as 
viewed in FIG. 2), a latch release paddle 30b carried on the underside of 
the leading edge of the pawl 30 will engage an L-shaped latch pin 34 in a 
tape follower arm 35 to release a spring loaded permanent magnet 36 
carried by the tape follower. The permanent magnet is held between pole 
pieces, as shown in FIG. 5, to form an erase head. When the gap of the 
erase head is against the tape during the last authorized play, it erases 
the tape as it passes through the tape deck onto the takeup reel. Since 
the magnet 36 may be released during a replay of a segment within a normal 
play, it is possible that only the last part of the tape will be erased as 
it is wound on the takeup reel. However, when the tape is rewound on the 
supply reel in order to play it again, the entire tape passes over the 
erase head, and is erased. 
As noted above, when the tape is transferred from the supply reel on the 
left to the takeup reel on the right, the follower arm 35 rotates 
clockwise (as viewed in FIG. 2), and vice versa. Thus, power that drives 
the follower arm is the transfer of tape from reel to reel. But as tape is 
transferred, the space between the two reels varies. This space variation 
is approximately 0.3 inches, and the spade is narrowest at the 50% full 
reel point. To accommodate this variation, the follower arm is designed to 
essentially follow the transferring tape reel dimensions with little or no 
gap at either end of a play or rewind cycle. This results in a transfer of 
the point of contact on the reels as the angle of the follower changes. 
Nubs of low friction material are provided on the end (both sides) at one 
extreme of the moving point of contact, and nearer to the pivot point 
(both sides) at the other extreme of the moving point of contact. These 
nubs are identified by reference numerals 37, 38, 39 and 40. When only nub 
37 is in contact with a near empty reel on one side, nub 39 is near 
contact with the full reel on the other side, and when only nub 38 is in 
contact with the other near empty reel, nub 40 is near contact with the 
other reel. 
FIGS. 7A through 7D illustrate the operation of the follower arm with four 
contact points at nubs 37, 38, 39, and 40 in a rewind sequence, starting 
in FIG. 7A with the takeup reel full, and the supply reel empty. Note the 
small gap at nub 38 with the hub of the supply reel, and the fact that the 
takeup reel has contact at only one point (nut 40). In FIG. 7B, the supply 
reel has filled sufficiently to make contact at one point (nub 38) of the 
follower arm, while the emptying takeup reel has lost contact. In FIG. 7C, 
the supply reel has filled sufficiently to transfer contact to a point 
(nut 39) at a shorter radius from the pivot of the follower arm. FIG. 7D 
illustrates the position of the follower arm after complete rewind. The 
process is reversed when transferring tape from the supply reel to the 
takeup reel. The interesting thing to note is that when the direction of 
tape is reversed, and tape is supplied from one reel to the other, the 
follower arm will not move until the receiving reel has received 
sufficient tape to make contact with one or two nubs on the follower arm. 
This hysteresis in the motion of the follower arm when reversing tape 
direction allows some segment of tape to be replayed without penalty. 
The hysteresis just referred to is more important in the second embodiment. 
In that embodiment shown in FIG. 3, the follower arm is designed with 
straight contact segments so that as tape is transferred, there are 
contact points along straight segments of the follower arm, as shown in 
FIGS. 7E through 7H, with tape now being transferred from the supply reel 
to the takeup reel. Note the tap at the takeup reel which provides a 
segment of tape to be transferred before the arm is contacted to pivot the 
arm counterclockwise, as shown in FIG. 7E. Contact on the takeup reel 
begins out on the end of the follower arm and moves along a straight 
segment until well past the 40% full mark shown in FIG. 7F, and then 
transfers to the longer straight segment. FIG. 7G shows this segment in 
contact with a 60% full mark and then in FIG. 7H with a 100% full mark in 
contact. By proper design of this follower arm, the hysteresis can be made 
not only to permit replay of segments, but also for the replay segment to 
be of the same length anywhere in the tape. 
Referring again to FIG. 2, the spring loaded magnet 36 is carried by an arm 
41 pivoted on a pin 42. As shown, the magnet arm 41 is held back against 
the force of a wishbone spring 43 by the tip 34a of the latch pin 34. This 
pin is provided with a sleeve 34b that is press fitted into a groove in 
the underside of the follower arm 35, with the leg of the latch pin 
opposite the tip 34a protruding through a vertical slot 46 in the follower 
arm. When the last authorized play cycle has caused the finger 30a of the 
pawl 30 to drop into the flot 20a of the ratchet wheel 20, the pawl 30 
pivots closkwise (as viewed in FIG. 2) causing the latch release paddle 
30b to engage the end of the latch pin 34 protruding from the slot 46, and 
pull it toward the pivot of the follower arm 35, toward a post 44 
extending between the two halves of the caseette. (Note that a spacer 45 
holds the follower arm up off the bottom half 11 of the cassette 
sufficiently for the follower arm 35 to pivot between the flanges of the 
supply and takeup reels free of any contact with the bottom half of the 
cassette.) Since the last authorized play could occur anywhere in the 
tape, the angular position of the follower arm (and therefore the latch 
pin 34) relative to the pawl paddle 30b could be anywhere between 
extremes. It is for that reason that the pawl paddle has been made 
arcuate; to be sure it engages the latch pin for any possible angular 
position of the follower arm 35. 
The follower arm 35 provides all of the power, and derives its power from 
the transferring tape. A slip clutch is therefore necessary to couple the 
follower arm 35 to the reciprocating lever 24. That clutch consists of a 
tab 47 secured to the Y-shaped lever 24 in the space 26 between the 
branches of the lever. The tap 47 extends downwardly from the lever 24, 
and carries a detent 48 which engages vertical grooves 49 on the end of 
the follower arm 35. As the follower arm moves in one direction, the 
detent slips over the end of the follower arm until it engages a groove 
49, and then forces the lever 24 to rotate with the follower arm over an 
arcuate distance set by the space between the branches of the Y-shaped 
lever arm. Motion is transferred to the ratchet wheel 20 by the wire pawl 
25 to advance the ratchet wheel, and thereby increase the count by one. 
Once the lever 24 has reached its limit of rotation (which is set to be 
just enough to advance the count by one), the pin 27 stops the lever, and 
the flexible tab 47 will allow the detent 48 to ride over grooves 49 on 
the end of the follower arm until the direction of tape motion is 
reversed. 
It should be appreciated that, as tape is transferred to the empty takeup 
reel on the right from the full supply reel on the left, the follower arm 
35 will not rotate at a uniform rate, although tape is fed from one to the 
other at a uniform linear rate. Consequently, it may be desirable to 
program the spacing between grooves 49 so that it increases from one side 
to the other, with the smaller spacing near the supply reel side. In that 
way the amount of rewind before engagement of the next groove may be 
programmed to allow the same length of replay along the entire length of 
the tape without advancing the count. Alternatively, the grooves may be 
programmed to permit replay without penalty only within defined segments 
of arbitrary length of recorded program. In addition, the spacing of the 
first groove from each side of the follower arm 35 allows for a segment of 
tape that may be replayed at the beginning and end of the tape an 
unlimited number of times without penalty to view previews and trailers. 
Although an erasing magnet is preferred as a means of preventing plays 
after the authorized number, it would be feasible to link a pawl 
equivalent to the pawl 30 to a brake locking mechanism. The existing 
brakes in a cassette are spring biased in the "brake set" position. A pin 
in the tape deck pushes a paddle to release the brakes when the cassette 
is inserted. The brake locking mechanism for this invention would consist 
of a spring biased lever pawl biased to lock the existing brakes after the 
cassette is removed from the tape deck following the last authorized play, 
as will be described more fully hereinafter with reference to FIG. 6. 
Again referring to FIG. 2, in order to prevent the ratchet wheel assembly 
from advancing during loading, testing and/or duplication, a plastic 
restraining tab 24c is molded as part of the reciprocating arm 24. This 
restraining tab passes through a notch 24e in the upper half 10 of the 
cassette and prevents reciprocating motion of the arm 24. Once duplication 
and testing has been completed, the restraining tab is removed from the 
outside of the sealed cassette, thereby activating the count wheel 
assembly. This restraining tab is made with a smaller diameter adjacent 
the reciprocating arm so that it will break there when it is removed. 
Still other variations will occur to those skilled in the art. An important 
variation to the embodiment of FIG. 2 is a friction clutch for coupling 
the follower arm to the reciprocating lever in place of a detent clutch. 
Its advantages are detection of a rewind started at any point in the tape, 
instead of at finite points with a detent clutch, and allowing a 
predetermined amount of replay before the start of another play cycle 
which will advance the play counter after a rewind is started. FIG. 3 
illustrates in an exploded view the essential parts of a friction coupled 
system. Note that significantly fewer parts are needed to accomplish the 
same functions as the embodiment of FIG. 2, and that the parts may be 
preassembled as a unit to be added to a conventional cassette over the 
brake area 13. 
A follower arm 50 has a specific shape, with the ends away from a pivot pin 
51 on both sides angled out slightly, as shown more clearly in FIGS. 7F 
through 7H. The shape is designed to vary the contact point as tape on the 
takeup reel builds up so that a proportional relationship between playing 
time and displacement angle of the follower arm is achieved. When the tape 
is rewound for the next play, the follower arm is not contacted by the 
supply reel for a predetermined time, and then as tape builds up on the 
supply reel, the arm is pivoted by the tape build up toward the takeup 
reel. Then when play is started, the arm is held in position by the 
friction clutch until tape builds up enough on the takeup reel to contact 
the arm. This gap between the arm and the tape when rewind is started, and 
again when play is started provides a hysteresis in the system that allows 
for limited rewind-play cycles to take place without advancing the play 
counter. In that way a limited segment may be replayed at any point in the 
tape without penalty. 
Stability of the follower arm 50 during handling and storage is maintained 
by the friction coupling link comprised of a friction disc 52 between the 
follower arm 50 and a counting ratchet wheel 53. In the case of extreme 
shock to the cassette, where the friction may be overcome by inertia 
forces, the free swing range of the follower arm will be less than the 
displacement needed to cause a count to be activated. 
The counting ratchet wheel 53 is comprised of a ratchet wheel with a count 
disc cemented onto it, or with numbers printed directly on it, and a 
ratchet pawl 54 on a pin 55. The pin 55 also serves to limit the rotation 
of the friction disc 52 to the space between two ears 52a and 52b. Note 
that the ratchet wheel is provided with a thick skirt 53a with an opening 
53b. The bottom of the skirt bears against the friction disc 52, which in 
turn bears against the follower arm 50. A base plate 56 secured over the 
tape guide walls around the brake area 13 (FIG. 1) allows the follower arm 
50 to pivot between the flanges of the supply and takeup reels free of any 
contact with the lower half of the cassette. A cap screw 57, a compression 
spring 58, and a nut 59 provide the compression necessary for the desired 
friction between the skirt 53a of the count wheel 53 and the friction disc 
52, and between the follower arm 50 and the friction disc 52. 
Carried by the follower arm 50 in a manner analogous to the embodiment of 
FIG. 2 is a magnet release pin 60, a tip 60a of which protrudes from a 
slot 61 in the follower arm 50. A wishbone spring 62 has the end of one 
branch connected to a magnet arm 63 and has the center pinned by a pivot 
pin 64. The end of the other branch bears against the back of the tip 60a 
of the pin 60. That tip 60a of the pin 60 in turn bears against the skirt 
of the count wheel 53. When the count wheel has advanced through a 
predetermined number of authorized plays, the opening 53b in the skirt 
will be positioned just next to the tip 60a of the pin 60. The next play 
of at least a segment more extensive than an authorized segment replay 
which is a function of the hysteresis of the follower arm 50, will then 
advance the count wheel, and the spring 62 will then force the tip 60a of 
the pin 60 into the opening 53b in the skirt 53a of the count wheel 53. 
This motion of the pin 60 releases the magnet arm 63, and the spring 62 
pivots the magnet arm 63 to place an erase head 63' shown in FIG. 5 
comprised of a permanent magnet and pole pieces with a narrow gap in 
contact with the tape on the takeup side. 
FIG. 5 shows the essential details of the magnet, a permanent magnet 66 
with north (N) and south (S) poles abutting pole pieces 67 and 68. These 
pole pieces are shaped to provide a gap 69 approximately 0.010 inches 
(0.25 mm). A plastic spacer may be used to maintain the gap. The small gap 
contains the magnetic flux within the immediate area. When the gap is 
brought near or against the tape, the flux will concentrate in a path 
through the magnetic material on the tape. In that manner, a high density 
flux in the tape is provided to erase the tape with no measurable field at 
a distance of about 0.10 inches (2.5 mm) or greater. By holding the gap of 
the pole pieces at a distance of more than 0.25 inches (6 mm) from the 
video tape until needed to erase, no unintentional damage can occur to the 
recorded video program. 
A summary of the friction coupled embodiment of FIG. 3 will now be 
presented. The starting conditions are: supply reel full, takeup reel 
empty, and follower in contact with the tape of the supply reel. This is 
the configuration that will occur after a full rewind has been made. 
(a) Play starts. 
1. Build up under the follower arm 50 starts on the takeup side. 
2. The tape unwinds from contact with the supply side of the follower arm 
at a short radius. 
3. Friction holds the follower arm 50 in place at this time. 
4. Tape will build on the takeup reel until contact near the tip of the 
follower arm 50 occurs. (The longer radius.) 
(b) The build up now causes the follower arm to rotate. 
1. The friction disc 52 couples the motion to the counting wheel 53. 
2. Counting action starts, as the wheel moves. 
3. When the next tooth passes under the pawl, the count advance has been 
completed. 
4. The engagement force of the pawl 54 will prevent reverse rotation of the 
counter wheel 53. 
5. The friction disc 52 has ears 52a and 52b to limit its rotation, thus 
preventing motion beyond that needed to register one count to be coupled 
to the count wheel 53. 
6. No further rotation of the counting wheel 53 can occur after the forward 
stop engagement of friction disc 52. 
7. The follower arm 50 now slips under the stopped friction disc 52 and the 
counter wheel 53 until the end of play occurs. Note that the count of the 
wheel 53 is always advanced on play. 
(c) Rewind cycle starts. 
1. As rewinding occurs, the follower arm 50 will remain in a fixed position 
until the build up on the supply reel engages it. 
2. The friction disc 52 now rotates in a reverse direction. 
3. Reverse rotation of the count wheel 53 is prevented by the pawl 54. 
4. Rotation of the friction disc 52 is allowed until the reverse stop ear 
is engaged. 
5. The follower arm 50 now slips under the friction disc 52 and count wheel 
53. This condition is maintained for the remainder of the rewind mode. 
A preferred embodiment of the follower arm 50 for the embodiment of FIG. 3 
is shown in FIG. 4, where the same reference numerals are used for the 
corresponding components. The magnet arm carried a magnet 63' inside pole 
pieces as shown in FIG. 5. The wishbone spring 62 is sandwiched between 
the tape follower arm 50 and the magnet arm 63 with the screw 64. A notch 
65 receives the pin 60 to hold the arm 63 back against the force of the 
spring 62. One end 62a engages the arm 63, and the other end 62b engages a 
notch 60b on the pin 60 which is carried by the arm 50. Blocks 50a and 50b 
on the follower arm provide a channel that helps guide the tip 60a of the 
pin 60 against the skirt 53a (FIG. 3) of the ratchet wheel counter 53. 
As noted hereinbefore, an alternative to erasing the tape, after a 
predetermined number of authorized plays, is to lock the reel brakes when 
the cassette is removed from the tape deck. An example of how this may be 
accomplished will now be briefly described with reference to FIG. 6, and 
the FIGS. 6A through 6F. 
Referring to FIG. 6, brake pawls 81 and 82 normally engage notches on the 
bottom flanges of the cassette reels shown in FIG. 1 when the cassette is 
removed from the tape deck. Springs 83 and 84 provide the force that 
pivots the brake pawls on posts 85 and 86 for engagement of the reel 
notches. These brake pawls are retracted against the force of the springs 
by an L-shaped lever 87 having a "paddle" portion 87a over a hole in the 
bottom half of the cassette, and an upright portion 87b. This lever pivots 
on a pin 88 held by the bottom half of the cassette. 
The lock on these brake pawls is comprised of a pawl 89 pivoted on a in 90, 
also held by the bottom half of the cassette. A spring 91 shown in FIG. 6a 
biases the pawl 89 against the sprocket wheel 92 used to count the 
authorized plays. 
A partially spiral shaped slot 93 in the sprocket wheel allows the pawl 91 
to move forward on the last authorized play, but at that time the brake 
pawls 81 and 82 are retracted by the lever 87 as shown in FIGS. 6B and 6C. 
FIG. 6B shows a pin 94 in the tape deck that pushes the paddle portion 87b 
back against levers 81a and 82a of the back pawls, and FIG. 6c shows the 
retracted position of brake pawls. 
At this time, the tape may be rewound and replayed again, but with added 
drag on the reels, since the sprocket wheel 92 cannot turn as the follower 
arm is pivoted during rewind and replay. Unauthorized plays will not be 
prevented until the cassette is withdrawn from the tape deck. At that 
time, the pin 94, as shown in FIG. 6E, retracts to allow the brake pawls 
to pivot out, as shown in FIG. 6F, into engagement with notches in the 
reels. As the portion 87b of the brake lever 87 pivots forward, the pawl 
89 also pivots forward under the force of the spring 91. As the pawl 89 
moves forward further into the slot 93, it causes the sprocket wheel 92 to 
rotate through a small angle due to the partial spiral shape of the slot. 
That shape is designed to provide an edge behind the pawl 92 when it has 
traveled into the slot 93 to the furthest point possible against its 
curved side of the slot, as shown in FIG. 6D. 
If an attempt is made to reinsert the cassette in a tape deck after the 
brakes have been locked, the pin 94 will not be able to pivot the portion 
87b of the brake lever 87 to release the brakes because of the pawl 89 in 
its forward position shown in FIG. 6E, and the back side of the partially 
spiral shaped slot 93 bearing against the back of the pawl 89. To try to 
force the cassette into the tape deck would only result in the portion 87a 
being bent up. To assure that, the pawl 89 is made of rigid material 
strong enough not to break, such as steel, while the brake lever 94 is 
made of relatively flexible material that is rigid enough to allow it to 
pivot for the normal brake setting purpose, yet flexible enough to bend 
and not break when the pawl 89 is in the locking position shown in FIG. 
6E. 
The locked reel will not only prevent further unauthorized replay of the 
tape, but also prevent removal of the tape from the cassette without 
opening the cassette. To prevent that, the two halves of the cassette are 
preferably welded together wherever there is contact, such as by sonic 
welding techniques. To prevent breaking or cutting the cassette open, the 
cassette may be leased, not sold, for the purpose of renting it out with a 
condition of the lease that the cassette not be opened.