Indexing means for tape cassette

A tape cassette has a springloaded indexing mechanism to urge the cassette reels in a tape winding directions so as to tension the free run of tape between the reels whenever the cassette is removed from the tape transport machine.

BACKGROUND OF THE INVENTION 
This invention relates to tape cassettes, and particularly to means for 
maintaining tape tension when the cassette is removed from the transport 
machine. 
Tape cassettes usually contain two reels with tape coiled thereon so as to 
present a free run of tape between the reels, this run being accessible 
along one side of the cassette that is either open or has a cover door 
that can be opened when the cassette is inserted into a tape transport 
machine (e.g., a magnetic tape recording, playing and rewinding machine). 
Usually also, the sides of the cassette adjacent and orthogonal to the 
open side have smaller openings for the lateral insertion of a capstan, 
play-record and erasing heads, and various guides, all of which are part 
of the transport machine but must engage the tape on the side thereof that 
faces toward the interior of the cassette. If the free run of tape is too 
loose, it may drop too far back into the cassette so that the capstan and 
other such elements fail to pass behind the free tape run and the machine 
cannot function to transport and record or play the tape; conversely, if 
the loose run of tape falls too far out of the cassette while it is being 
loaded, the tape may become tangled in the transport interior mechanism 
and other malfunctions will result. Also, if the reels are loose when the 
cassette is being shipped or handled outside the transport machine, then 
vibrations or other sudden jolts may cause the tape coils to unwind 
somewhat and sag into conical shapes, resulting in immediate or eventual 
tape edge damage and later guiding malfunctions in the transport machine. 
Previously in the art it has been attempted to control this problem by 
arranging springloaded friction brakes or pawl-and-pinion combinations 
within the cassette to lock or restrain the reels in the positions that 
they occupy at the moment the cassette is withdrawn from the transport 
machine; and portions of the transport mechanism are arranged to engage 
the pawls directly or indirectly as the cassette is loaded into the 
transport to cause the pawls to retract and free the reels while the 
cassette remains in the machine-loaded condition. Such an arrangement is 
shown in U.S. Pat. No. 3,900,172, in which the cassette cover door is 
opened automatically by mechanism within the transport as the cassette is 
loaded, and the door in turn retracts the pawls that engage pinion gear 
teeth on the cassette reels. 
Such arrangements are limited, however, to perpetuating the tape tension or 
tape slack conditions that exist at the moment when the cassette is 
removed from the machine, and the run of tape at the open side of the 
cassette may still be too loose for proper functioning at the time of the 
next subsequent insertion. Nothing positive is done to ensure that the 
tape is actually placed under tension if it is not already in tensioned 
condition. 
Therefore it is an object of the present invention to ensure that the tape 
is always under tension when the cassette is removed from the transport 
machine. 
BRIEF DESCRIPTION OF THE INVENTION 
This and other objects are achieved in a cassette having a springloaded 
indexing mechanism to urge the reels in a tape winding direction so as to 
positively tension the free run of tape between the reels whenever the 
cassette is removed frow the transport machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show a generally rectangular cassette 11 having a top 12, 
bottom 13, end walls 14 and 15, a back wall 16, and an open front side 17 
at which a free tape run 18 is presented as by means of guides 19. The 
tape is coiled in opposite directions on a pair of reels 21, 22, the hubs 
and flanges of which show only in phantom in FIG. 2, but each reel has a 
lower concentric extension formed as a pinion gear with gear teeth 23 and 
a central arbor hole 24 for impalement on respective mounting arbors of 
the tape transport machine (not shown); these pinion extensions show in 
cross-section in FIG. 2. 
Whenever the cassette is not in the transport machine, the reels 21, 22 are 
loosely positioned in the cassette by means of the extensions bearing 
pinion teeth 23, portions of the extensions extending downwardly through 
openings 26 in the bottom wall 13 of the cassette; each of the openings 26 
is circumvallated by a raised rib 27, which is arranged to bear against 
and support the bottom flange of the respective reel. Each rib 27 has an 
opening 28 for the insertion of a tooth portion 31 of a rack assembly 32 
comprising a carrier member 33 on which are pivoted two pawls 34 as by 
means of pivot pins 36. The teeth 31 are actually formed on the pawls 34, 
and the pawls are springloaded as by springs 37 to be urged in the 
direction of engagement with the respective pinion teeth 23 of the reels. 
The rack carrier member 33 is mounted for sliding motion in a direction 
perpendicular to the plane joining and containing the two reel axes, and 
along a path that is midway between the reels, and is springloaded as by a 
compression spring 38 to carry the pawls 34 into engagement with the 
pinion teeth 23 and to load each of the reels in a winding direction to 
positively tension the tape run 18. 
Each of the pawls 34 has an arm 41 extending to a position at which 
openings 42 are provided in the bottom wall 13 of the cassette for access 
by a pair of key elements 43 from the transport mechanism, and for 
movement of the keys 43 in a downward direction (i.e., toward the bottom 
of the drawing of FIG. 2) to cause retraction of the pawl teeth 31 from 
the pinion teeth 23 in a radial direction that has at least a directional 
component parallel to the plane of the reel axes. Compounded with this 
motion, the rack carrier member 33 is caused to move upwardly (i.e., 
toward the top of the drawing of FIG. 2) as by means of a pivoting key pin 
44 extending from the transport mechanism and riding in an opening 46 in 
the cassette bottom 13. The carrier member 33 also has a central opening 
47 by which the member rides in sliding motion on a pair of track bolts, 
which also serve to retain a retaining plate 48 that partly overlies and 
guides the member 33 in its sliding motion, and serves also to assist in 
retaining one end of the spring 38. 
For some purposes, the rack and pinion combination may be arranged in 
simpler form, as shown for example in FIG. 3, in which a rack plate 33a is 
arranged for the same springloaded and pin retractable rectilinear motion 
as the member 33 of FIG. 2; and the plate 33a has one more guide 51 
extending from the cassette bottom wall and riding in a slot 52 in the 
plate 33a. A pair of rectilinear arrays of rack gear teeth 31a are formed 
on the sides of the plate 33a to engage the pinion teeth 23 and load the 
reels in the tape winding direction. The advantage of the arrangement of 
FIG. 3 is the simpler structure, without need for the pawls 34 or the 
transport keys 43. However, the arrangement of FIG. 3 does require a much 
longer path of motion for the plate 33a to ensure both adequate loading of 
the reels and tensioning of the tape in one direction, together with 
adequate retraction to completely clear the teeth 23 in the other 
direction; and if the reels fit too loosely in the cassette, there may be 
risk that the teeth of plate 33a may slip out of engagement with the 
pinion teeth 23. For the use contemplated for the actual invention as 
constructed, the arrangement of FIG. 2 has been found to provide more 
security of operation in a more compact form.