Tape guide for guiding magnetic tape in a videotape cassette

A tape guide for use in a magnetic tape cassette for guiding the magnetic tape includes a cylindrical member having a slit extending along its length. The slit defines first and second edge forces that face each other. In one embodiment, a plurality of tabs are connected to the first and second edge faces of the cylindrical member and extend towards the oppositely positioned edge face. The tabs overlap one another and serve to inhibit the tape guide from becoming interlocked with another tape guide. In another embodiment, a plurality of outdented portions extend from both edge faces and each outdented portion is positioned opposite to an indented portion on the opposite edge face.

BACKGROUND AND SUMMARY OF THE PRESENT INVENTION 
The present invention relates to videotape cassettes containing magnetic 
tapes. More particularly, the present invention concerns a tape guide that 
is adapted to be positioned on the interior of the videotape cassette for 
guiding the magnetic tape as it passes from spool to spool. 
Tape guides are a necessary part of every videotape cassette in order to 
ensure that the tape is properly guided and fed to the access opening at 
the front edge of the videotape cassette when the cassette is inserted 
into the tape deck for playing. The number of tape guides produced 
annually in order to meet the needs of the magnetic tape cassette 
manufacturing industry is enormously large. At the very least, the number 
of tape guides produced annually is in the neighborhood of several hundred 
million. Thus, it can be readily seen that any cost reduction that can be 
achieved with respect to the manufacture of a single tape guide can result 
in significant overall cost savings when considered in light of the total 
number of tape guides manufactured. 
Typically, a hollow stand-alone tape guide for use in a videotape cassette 
is manufactured from stainless steel having a thickness of approximately 
0.021-0.022 inches and in some cases, as thin as 0.015 inches. After the 
tape guide has been manufactured from the aforementioned material, it is 
subjected to chemical treatment as well as polishing and finishing 
operations in order to ensure that the exterior finish on the tape guides 
is smooth and free of any burrs or other foreign material and so smooth 
that it does not adversely affect magnetic tape sliding on its surface. 
The magnetic tape contained in the videotape cassette is made of a highly 
sensitive material that can be very easily damaged through contact with 
rough surfaces and the like. Thus, the aforementioned chemical treatment 
and polishing and finishing operations are necessary in order to produce a 
tape guide whose exterior surface has a very high quality finish. In that 
way, the magnetic tape that passes around the tape guide will not become 
damaged as a result of contact with burrs or other types of foreign 
objects located on the exterior surface of the tape guide. 
The finish required on the exterior surface of the tape guide, otherwise 
described as the surface roughness, can be expressed numerically in 
microinches. The numerical designation represents the arithmetic average 
deviation of the exterior surface from the mean line in a profile. The 
desired roughness for the exterior surface of a tape guide for use in 
guiding the magnetic tape in a videotape cassette should preferably be 
about eight microinches. It is rather evident that such a smooth, high 
quality surface finish requires extensive chemical treatment and finishing 
and polishing which can significantly increase the cost associated with 
producing the tape guide. 
From the foregoing discussion, it can be seen that it would be highly 
desirable to manufacture a tape guide for use in a videotape cassette that 
possesses all of the necessary physical properties and structural features 
required of the tape guide but which is thinner. The manufacture of a 
thinner tape guide would permit the realization of substantial cost 
savings. 
The manufacture of a tape guide from thinner material does, however, raise 
a concern that when the tape guide interacts with another tape guide such 
as during chemical treatment, polishing, finishing or handling of the tape 
guide, the two tape guides will become interlocked with one another. When 
a tape guide is manufactured as a one piece unit with a slit extending 
longitudinally along its length, a gap is formed in the unit as a result 
of the slit. In prior art stand-alone tape guides, the thickness of the 
material used to manufacture the tape guides was greater than the width of 
the gap. Hence, it was quite unlikely that one tape guide would become 
interlocked with another tape guide because the tape guide was not thin 
enough to fit into the gap formed by the slit. 
However, the manufacture of a tape guide from much thinner material raises 
the possibility that the tape guide will become interlocked with another 
tape guide during the finishing, chemical treatment and handling of the 
tape guide because the thickness of the material is less than the width of 
the gap in the tape guide formed by the slit. Since the thickness of the 
material used to manufacture the tape guide is less than the width of the 
gap formed by the slit, it is highly probable that while the tape guide is 
interacting with other tape guides, one tape guide will be pushed into the 
slit in another tape guide to thereby result in the two tape guides 
becoming interlocked with one another. 
The problems resulting from interlocked tape guides are readily apparent. 
The time and cost associated with attempting to separate the interlocked 
tape guides are highly undesirable. Further, in light of the smooth and 
high quality exterior finish that is required of the tape guides in order 
to avoid damaging the magnetic tape, there exists the possibility that the 
interlocking of two tape guides will cause damage to the exterior surface 
of the tape guides. Similar damage may result from any attempt to separate 
the tape guides after they have become interlocked. 
It can be seen from the foregoing discussion that there exists a need in 
the art for a tape guide that is manufactured from thinner material so as 
to be less expensive. It is further apparent that there exists a need for 
a thinner, less expensive tape guide that is not susceptible to becoming 
interlocked with other tape guides. 
The aforementioned problems are overcome and the foregoing objectives are 
achieved by the tape guide according to the present invention. The tape 
guide includes a substantially tubular, longitudinally extending member 
having first and second oppositely located ends and having interior and 
exterior surfaces. A slit extends along the entire length of the 
substantially tubular member to define first and second spaced apart and 
facing edge faces. An arrangement is attached to the substantially tubular 
member for inhibiting other tape guides from extending through the slit 
and becoming interlocked with the substantially tubular member. A groove 
can be located in each end of the substantially tubular member for 
properly orienting the tap guide when it is positioned in the magnetic 
tape cassette. 
One embodiment of the arrangement for inhibiting other tape guides from 
extending through the slit in the cylindrical member includes a plurality 
of first tabs connected to the first edge face of the substantially 
tubular member and extending toward the second edge face and a plurality 
of second tabs connected to the second edge face of the substantially 
tubular member and extending towards the first edge face. Each one of the 
first tabs overlaps one of the second tabs and slots are provided adjacent 
the first tabs for slidably receiving the second tabs while slots are 
provided adjacent the second tabs for slidably receiving the first tabs. 
An additional embodiment of the arrangement for inhibiting another tape 
guide from extending through the slit in the cylindrical member includes 
outdented portions extending from the first edge face that are positioned 
opposite to indented portions in the second edge face and outdented 
portions extending from the second edge face that are positioned opposite 
to indented portions in the first edge face.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A videotape cassette includes a lower section 10, a portion of which is 
shown in FIG. 1, as well as an upper section (not shown). Two tape reels 
12, 13 are contained in the lower section 10 and arranged to be rotatable. 
Magnetic videotape 14 is wound on the reels 12, 13. The magnetic video 
tape 14 extends from one reel 12, past a tape guide 16, past an access 
opening located along the front edge of the lower section 10, past another 
tape guide 16 and around the other reel 13. The tape guides 16 are located 
along the front edge of the lower section 10. An upper section of the tape 
cassette (not shown) mates with the lower section 10 of the tape cassette 
to enclose the magnetic tape 14. 
The tape guide 16 includes a one piece, substantially tubular member 18 as 
seen in FIG. 2. The member 18 is circular in cross-section and has an 
inner surface 21 and an outer surface 23. Extending along one side of the 
tubular member 18 is a slit 20. 
The member 18 is substantially cylindrical and has a first end 22 and a 
second oppositely located end 24 as illustrated in more detail in FIG. 3. 
The slit 20 extends longitudinally along the entire length of the 
cylindrical member 18. The slit defines a first edge face 26 and a second 
edge face 28 that is positioned opposite to the first edge face 26. The 
first and second edge faces 26, 28 face each other and are spaced from one 
another so as to define a gap between the two edge faces 26, 28. 
A substantially V-shaped groove 30 extends inwardly from the first end 22 
of the cylindrical member 18 and another substantially identical V-shaped 
groove extends inwardly from the second end 24 of the cylindrical member. 
The two V-shaped grooves are longitudinally aligned with respect to each 
other and the slit 20 extending along the length of the cylindrical member 
18 extends between the base portion 34 of the one V-shaped groove 30 and 
the base portion 36 of the other V-shaped groove 32. The V-shaped grooves 
30, 32 are adapted to mate with corresponding elements (not shown) on the 
lower section 10 and the upper section (not shown) of the videotape 
cassette in order to ensure that the tape guides 16 do not rotate relative 
to the upper and lower sections of the videotape cassette. Further, the 
V-shaped grooves 30, 32 and their relationship with respect to the slit 20 
serves to properly orient the tape guides relative to the magnetic tape 
14. That is to say, the sensitive nature of the magnetic tape 14 is such 
that if the magnetic tape 14 were to slide over the slit 20 in the 
cylindrical member 18, the magnetic tape 14 could become damaged. Thus, 
the slit 20, the V-shaped grooves 30, 32 and the corresponding mating 
elements (not shown) on the upper and lower sections of the video tape 
cassette are positioned so that the slit 20 will be positioned away from 
the portion of the tape guides 16 over which the magnetic tape 14 slides. 
In that way, no damage will occur to the magnetic tape 14. 
The tape guide 16 is manufactured from stainless steel having a very small 
thickness. The thickness of the stainless steel material is less than 
0.014 inches. More particularly, the thickness of the material is 
approximately 0.007-0.009 inches and preferably approximately 0.008 
inches. 
Sheets of stainless steel are passed through several forming stations in a 
progressive die in order to form the substantially cylindrical member 18. 
The manufacturing process is such that upon exiting the progressive die, 
the cylindrical member 18 includes the slit 20 that extends longitudinally 
along the entire length of the cylindrical member 18. The stainless steel 
material used to manufacture the tape guide 16 possesses a certain memory 
or hysteresis that tends to maintain a predetermined gap between the first 
and second edge faces 26, 28 of the slit 20 after the cylindrical member 
18 exits the die. It has been found that a gap of approximately 0.010 
inches exists between the first and second edge faces 26, 28 of the slit 
20 after the tape guide exits the die. 
In the case of a prior art stand-alone tape guide, stainless steel having a 
thickness of between 0.021 and 0.022 inches is commonly used for 
manufacturing the tape guide, although stainless steel having a thickness 
of 0.015 inches has also been employed. The interaction which occurs 
between tape guides having such a thickness during chemical treatment, 
finishing, polishing and handling of the tape guides does not pose any 
particular problem with respect to the interlocking of the tape guides 
because the thickness of the tape guide is greater than the width of the 
gap between the edge faces of the slit. That is to say, since the 
thickness of the tape guides is no greater than 0.015 inches, it is not 
likely that one tape guide will extend through the 0.010 inch gap between 
the edge faces of the slit in another tape guide and thereby become 
interlocked. As a result, when the prior art tape guide is being 
chemically treated, finished, polished and otherwise handled, the tape 
guide will remain separated from other tape guides. 
However, the present inventors have discovered that the use of 
substantially thinner material in the manufacture of a tape guide 
according to the present invention presents the possibility that the tape 
guide will become interlocked with another tape guide during chemical 
treatment, finishing, polishing and other handling. That possibility 
exists because the thickness of the material, 0.007-0.009 inches, is less 
than the width of the gap, 0.010 inches, between the edge faces of the 
slit. Accordingly, it is not uncommon that, when the tape guide is 
subjected to interaction with other tape guides during the chemical 
treatment, finishing, polishing and other handling of the tape guides, two 
or more tape guides will become interlocked. 
In recognition of the aforementioned drawback, the tape guide according to 
the present invention is designed so as to substantially eliminate the 
possibility that one tape guide will become interlocked with another tape 
guide. In that regard and as shown in FIG. 3, an arrangement is provided 
for inhibiting another tape guide from extending through the slit 20 and 
becoming interlocked with the tape guide 16. That arrangement includes a 
plurality of tabs 40, 42, 44 and 46, each of which is connected to the 
tubular member 18 and extends across at least a portion of the gap defined 
by the slit 20. Each of the tabs 40, 42, 44, 46 extends over less than the 
entire longitudinal extent of the cylindrical member 18. 
Two of the tabs 44, 46 are shown in more detail in FIG. 4. It is to be 
understood that the tabs 40, 42 are substantially the same as the tabs 44, 
46 shown in FIG. 4 and thus, the following description relating to the 
tabs 44, 46 is equally applicable to the tabs 40, 42. One of the tabs 44, 
as seen in FIG. 4, is connected to the first edge face 26 of the 
cylindrical member 18 and extends towards the second edge face 28 of the 
cylindrical member 18. The other tab 46 is connected to the second edge 
face 28 of the cylindrical member and extends toward the first edge face 
26 of the cylindrical member. The tabs 44, 46 are preferably positioned in 
pairs so that the two tabs 44, 46 overlap each other over at least a 
portion of their length. The overlapping portions of the tabs 44, 46 
ensure that at selected portions along the length of the slit 20, the gap 
between the first and second edge faces 26, 28 is reduced to an extent 
such that the gap between the edge faces 26, 28 is less than the thickness 
of the cylindrical member 18. By reducing the distance between the edge 
faces 26, 28 in that manner, the tape guide 16 is inhibited from becoming 
interlocked with another tape guide. 
The tabs 44, 46, as illustrated in FIG. 5, are preferably designed to 
overlap one another to an extent such that if the gap between the first 
and second edge faces 26, 28 is slightly larger than 0.010 inches due to 
design tolerances, the tabs 44, 46 will remain overlapped. The tabs 44, 46 
are also preferably designed so that when the tape guide 16 is in its 
relaxed state and is not subjected to any forces, the free end of the tab 
44 is spaced from the second edge face 28 of the cylindrical member 18 
while the free end of the tab 46 is spaced from the first edge face 26 of 
the cylindrical member 18. 
It can be seen from FIG. 6 that the tab 44 is connected to the first edge 
face 26 such that the surface 48 of the tab 44 is flush with the inner 
surface 21 of the cylindrical member 18. Similarly, the tab 46 is 
connected to the second edge face 28 such that the surface 50 is flush 
with the other surface 23 of the cylindrical member 18. Further, the 
thickness of each of the tabs 44, 46 is less than the thickness of the 
cylindrical member 18. The tabs 44, 46 are formed by a coining operation. 
The distance between the first and second edge faces 26, 20 defines the 
width of the slit 20. As pointed out above, the width of the slit 20 is 
greater than the thickness of the cylindrical member 18 when the 
cylindrical member is not subjected to any forces. The tabs 44, 46 serve 
to reduce the width of the slit 20 to an effective width that is less than 
the thickness of the cylindrical member 18. In that way, another tape 
guide is inhibited from extending through the slit 20 and into the tape 
guide 16. 
As also shown in FIG. 6, a slot 52 is positioned in the first edge face 26 
of the cylindrical member 18. The slot 52 is located above the tab 44 
between the outer surface 23 of the cylindrical member 18 and the tab 44. 
Another slot 54 is positioned in the second edge face 28 of the 
cylindrical member 18. The slot 54 is located below the tab 46 between the 
inner surface 21 of the cylindrical member 18 and the tab 46. The slot 52 
is positioned opposite to the tab 46 and is dimensioned to slidably 
receive the tab 46 when the tape guide 16 is subjected to a force that 
tends to push the first and second edge faces 26, 28 of the cylindrical 
member 18 towards one another. In a similar manner, the slot 54 is 
positioned opposite to the tab 44 and is dimensioned to slidably receive 
the tab 44 when the tape guide 16 is subjected to a force that tends to 
push the first and second edge faces 26, 28 of the cylindrical member 18 
towards one another. The slots 52, 54 are configured so that they are open 
to the exterior and interior respectively of the cylindrical member 18. 
The slots 52, 54 permit the tape guide 16 to give or deflect when subjected 
to a compression force so that the tape guide 16 will not become deformed. 
When the tape guide 16 is subjected to a compression force, the first and 
second edge faces 26, 28 will be forced towards one another and the tabs 
44, 46 will slide relative to each other with the tab 44 moving toward the 
second edge face 28 and the tab 46 moving toward the first edge face 26. 
If the tape guide 16 is subjected to a large compression force, the tab 44 
will be able to slide into the slot 54 and at the same time, the tab 46 
will be able to slide into the slot 52. 
The ability of the tape guide 16 to be compressed without being deformed as 
a result of the slidably interfitting tabs 44, 46 and slots 52, 54 is 
desirable because any deformations on the exterior surface of the tape 
guide can cause damage to the magnetic tape. Since the guide tapes 16 can 
deflect when subjected to a compressive force, the possibility that the 
tape guide will be deformed is reduced and thus, the integrity of the 
magnetic tape that passes over the tape guide can be maintained. 
Although the tape guide 16 has been described above as including two pairs 
of oppositely positioned overlapping tabs 40, 42, 44, 46, it is to be 
understood that other arrangements could also be employed while still 
maintaining the underlying purpose of preventing the tape guide from 
becoming interlocked with another tape guide. For example, more than two 
pairs of oppositely positioned tabs could be placed along the first and 
second edge faces 26, 28 of the cylindrical member 18. Alternatively, the 
tabs could be staggered along the first and second edge faces 26, 28 of 
the cylindrical member 18 so that the tabs are not oppositely positioned 
with respect to one another. In such an embodiment, each of the tabs 
should still extend more than halfway across the gap formed by the slit 20 
so as to ensure that the tape guide cannot become interlocked with another 
tape guide. It may also be desirable to provide a single pair of 
oppositely positioned overlapping tabs that are located midway along the 
length of the slit 20. As an alternative to the arrangement depicted in 
FIG. 6 where the tabs 44, 46 are of substantially the same length and each 
tab 44, 46 extends slightly more than halfway across the gap formed by the 
slit 20, the oppositely positioned tabs in each pair can be of different 
lengths with one of the tabs of the pair extending farther across the gap 
than the tabs depicted in FIG. 6 and the other tab of the pair extending 
not as far across the gap as the tab shown in FIG. 6. In that arrangement 
the tabs should still be designed to overlap one another by a small 
amount. As an additional alternative, it may be desirable to simply 
include a single unopposed tab extending from either the first edge face 
or the second edge face. In all of the above-described alternatives, the 
arrangement of the tab or tabs is such that the width of the slit in the 
cylindrical member is reduced to an effective width that is less than the 
thickness of the cylindrical member. 
A second embodiment of the arrangement for inhibiting another tape guide 
from extending through the slit 20 and becoming interlocked with the tape 
guide 16 includes, as shown in FIG. 7, inwardly curved portions 66, 76 of 
the first surface 26 that extend away from the second surface 28 so as to 
form indented areas. Outwardly curved portions 60, 70 of the first edge 
face 26 extend toward the second edge face 28 so as to form outdented 
areas. The second edge face 28 includes inwardly curved portions 62, 72 
that extend away from the first edge face 26 so as to form indents in the 
second face 28 and outwardly curved portions 64, 74 that extend toward the 
first edge face 26 so as to form outdents in the second face. 
The outdented portions 60, 70 extending from the first edge face 26 are 
positioned opposite to the indents 62, 72 in the second edge face 28. 
Similarly, the outdented portions 64, 74 extending from the second edge 
face 28 are positioned opposite to the indented portions 66, 76 in the 
first edge face 26. 
It can be readily seen that the tape guide 16 of the present invention as 
illustrated in FIG. 7 is inhibited from becoming interlocked with another 
tape guide due to the interfitting nature of the outdented portions 60, 
70, 64, 74, and the indented portions 62, 72, 66, 76, respectively. 
Although the outdented portions 60, 70, 64, 74, and the indented portions 
62, 72, 66, 76, do not contact one another, the tape guide 16 is inhibited 
from becoming interlocked with another tape guide as a result of the fact 
that the outdented portions 60, 70 extend beyond the plane of the second 
edge face 28 while the outdented portions 64, 74 extend beyond the plane 
of the first edge face 26. Thus, because the outdented portions extend 
across the gap formed by the slit 20, it is very unlikely that another 
tape guide will be able to extend through the slit 20 so as to become 
interlocked with the tape guide 16. In a manner similar to that noted 
above with respect to the embodiment depicted in FIG. 3, the arrangement 
shown in FIG. 7 serves to reduce the width of the slit 20 to an effective 
width that is less than the thickness of the cylindrical member 18. 
While the embodiment depicted in FIG. 7 is shown and described as including 
two outdented portions and two indented portions on each of the edge faces 
26, 28, it should be understood that more than or less than two outdented 
and two indented portions may be provided on each edge face 26, 28. 
Since the tape guides 16 are manufactured from thinner material than prior 
art stand-alone tape guides cost, savings can be achieved in two respects. 
First, material costs associated with the manufacture of the tape guide 
can be significantly reduced. In particular, at least a fifty percent 
reduction in material costs can be realized through use of thinner 
material as described above. Second, since the initial production of 
thinner material requires more rolling and forming steps than the initial 
production of thicker material, the exterior surface of the thinner 
material tends to possess an exterior surface that is smoother and that 
has a higher quality finish. Because a tape guide requires a very high 
quality exterior finish in order to ensure that the magnetic tape which 
slides over the tape guide is not damaged, the use of thinner material to 
manufacture the tape guides reduces the costs associated with chemically 
treating, finishing and polishing the tape guide as a result of the fact 
that the thinner material possesses a smoother exterior surface and 
consequently, less chemical treatment, finishing and polishing of the tape 
guide is required. The tape guide according to the present invention 
should preferably have a surface roughness of eight microinches or less in 
order to ensure that the magnetic tape that slides over the tape guide is 
not damaged. A further benefit associated with the manufacture of a tape 
guide from thinner material is that the time required to manufacture the 
tape guide is reduced because the tape guide need not be subjected to the 
same amount of chemical treatment, finishing and polishing as a thicker 
tape guide. 
The principles, preferred embodiments and modes of operation of the present 
invention have been described in the foregoing specification. However, the 
invention which is intended to be protected is not to be construed as 
limited to the particular embodiments disclosed. Further, the embodiments 
described herein are to be regarded as illustrative rather than 
restrictive. Variations and changes may be made by others without 
departing from the spirit of the present invention. Accordingly, it is 
expressly intended that all such variations, modifications, changes and 
equivalents which fall within the spirit and scope of the present 
invention as defined in the claims, be embraced thereby.