Cleaning apparatus for magnetic tape

An apparatus for cleaning the edges of a magnetic tape cut into final-product widths from a wide raw material web with which magnetic powder shed from the tape and base film dust breaking off in the cutting process are removed without damage to the tape. The apparatus includes an air bearing guide for floating the magnetic tape as it is transported thereon, a cleaning device positioned at a side of the guide and making contact with at least one edge of the magnetic tape, and a magnet device for urging the edge of the tape into close contact with the cleaning device.

BACKGROUND OF THE INVENTION 
The present invention relates to a cleaning apparatus for magnetic tape, 
and more particularly to a cleaning apparatus for magnetic tape cut from a 
wide raw material web of magnetic tape into a magnetic tape in 
final-product form in a specific width. 
Recently, magnetic tape has been widely used in many fields following 
improvements in various performance characteristics thereof. Magnetic tape 
is usually initially manufactured in the form of a wide raw material web 
of which is much wider than the magnetic tape of the final product. The 
wide raw material web is cut into magnetic tapes of specified 
predetermined widths in a cutting process. 
In the cutting process, an apparatus to cut the wide raw material web of 
magnetic tape is obviously required. The product quality of the final 
product is strongly affected by the cutting quality, namely, by the 
accuracy and neatness of the cutting process. That is to say, if the 
cutting quality is poor, dust particles, which result from the shedding of 
magnetic powder or tape base material from the cut edges of the tape, may 
be generated in significant amounts. The dust particles are carried on the 
surface of the cut magnetic tape, causing many kinds of problems during 
usage such as signal drop-out during recording and reproducing or head 
clogging in the recording-reproducing apparatus. Moreover, even if such 
dust particles are not shed, depending upon the amount of deterioration of 
the cutting quality, the surface accuracy of the cut edges may be 
unacceptable, and the same problems such as occur in the case of dust 
particle generation arise during recording and reproducing. 
Techniques have been proposed to remove the dust particles from the surface 
of the magnetic tape. A cleaning apparatus for magnetic tape such as 
disclosed in U.S. Pat. No. 4,213,222 has been applied to clean the surface 
of a tape by means of an unwoven material and a magnet after the tape has 
been cut into the predetermined width. As this apparatus was merely 
applied to clean the front and back surfaces of the cut tape, it was easy 
to ensure close contact between the cleaning device and the tape surface 
to be cleaned, even if the contact pressure exerted by the magnet on the 
tape was only roughly adjusted. 
However, employing a cleaning apparatus of this kind to clean the tape 
edges is accompanied by another problem, namely, the pressure in the 
transverse direction used to achieve contact between the edges of the 
magnetic tape and the cleaning device cannot be satisfactorily regulated 
to hold the position of the tape edges within a desired range of 
tolerance. These pressure variations are due to variations in the tape 
tension during tape transport and fluctuations in the amount of friction 
between the magnetic tape and the tape guides. The edges of the tape can 
be damaged if the contact pressure between the edges and the cleaning 
device is too strong, and cleaning cannot be properly achieved if the 
contact pressure is too weak. 
Especially for magnetic tapes used for video recording and reproduction, 
since the audio signal and the tracking signal must be recorded in side 
portions of the tape surface near the tape edges, the tape edge quality is 
very important to fully realize good tape performance. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a cleaning 
apparatus for magnetic tape which can solve the problems related to the 
shedding of magnetic powder and base film dust which breaks off in the 
cutting process and tape edge damage caused during the cleaning process so 
as to manufacture magnetic tape with superior reliability. 
In accordance with the above and other objects of the present invention, 
there is provided a cleaning apparatus for magnetic tape characterized by 
comprising: 
(a) an air bearing guide which floats the magnetic tape in order to 
transport the tape thereon, 
(b) cleaning means positioned at the side of the air bearing guide to make 
contact with at least one edge of the magnetic tape, and 
(c) a magnet which causes the at least one edge of the tape to closely 
contact the cleaning means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIGS. 1 and 2, an air bearing guide is supplied with air into 
an air inlet 8 introduced from an air supplying device such as a 
compressor (not shown). The air is blown from the outlet holes against a 
magnetic tape 5 which is passing thereon. Of course, the air bearing guide 
is not restricted to the example shown in FIGS. 1 and 2. For instance, the 
air bearing guide may be made from a porous sintered metal having a large 
number of small holes. 
The cleaning material may be formed by a strip-like materials such as a 
long unwoven fabric 7, for example, which is transported while contacting 
an edge 5a of the magnetic tape 5. That is, rolled unwoven fabric 7 from a 
supply roll 3 is taken up at an appropriate speed onto another roll 4 
while contacting the edge 5a of the magnetic tape 5. Furthermore, a 
permanent magnet 2 is positioned with the unwoven fabric on the opposite 
side of the tape edge 5a to attract the magnetic tape 5 while it is being 
transported under a floating effect by the air bearing guide 1 in order to 
achieve close contact with the unwoven fabric 7. Although the transport 
direction of the unwoven fabric 7 is preferably opposite to that of the 
magnetic tape, the spirit and scope of the present invention are not 
restricted in this specific example. For example, a lapping tape 
containing abrasive powder with an average diameter of 0.1 to 2.0 .mu.m 
can also be used as the cleaning device instead of the unwoven fabric of 
the above example. 
A cleaning apparatus constructed in accordance with the present invention 
can stably achieve the desired contact between tape edge 5a and the 
unwoven fabric 7 due to the floating effect caused by the air bearing 
guide 1 and the attractive force of the permanent magnet 2 simultaneously 
stabilizing the edge movement in the transverse direction. As a result, 
the occurrence of tape edge damage is prevented, thereby meeting the 
objects of the invention. 
Also, an electromagnet can be used in the practice of the present invention 
instead of the permanent magnet 2. In the case of an electromagnet, the 
contact pressure between the magnetic tape 5 and the unwoven fabric 7 can 
easily be controlled by adjusting the voltage supplied to the 
electromagnet in accordance with variations in the magnetic tapes and the 
transport velocity. 
Moreover, although in the above example the transport direction of the 
unwoven fabric 7 is parallel to that of the magnetic tape 5, the spirit 
and the scope of the present invention are not merely restricted to this 
specific example. For example, the transport direction of the unwoven 
fabric 7 and that of the magnetic tape 5 can be made oblique to one 
another in order to widen the contact area between the unwoven fabric 7 
and the magnetic tape 5. In such a case, the unwoven fabric surface is 
more effectively used, and contact between a fresh surface of the unwoven 
fabric and the edge of the magnetic tape is kept all the time. Hence, a 
much better cleaning effect is achieved. 
The cleaning apparatus of the above example can provide magnetic tape 
products of good quality and condition through continuous manufacturing 
processes such as a cutting process in which the raw material tape web is 
cut into magnetic tapes 5 of predetermined width, a winding process in 
which the cut tape is taken up onto rolls of a long length, and a cleaning 
process in which dust particles generated in the former cutting process 
are removed by the cleaning of the tape edges. 
Although in the above example cleaning of the tape edges is achieved for 
only one tape edge, the spirit and the scope of the present invention 
again are not restricted to this specific example. For example, another 
cleaning apparatus including an air bearing guide, permanent magnet and 
unwoven fabric can be employed to clean the other tape edge 5b in a 
continuous process. 
A stable tape edge cleaning process is achieved because the cleaning 
apparatus in accordance with the present invention can achieve the desired 
contact under stable conditions between the tape edges and the unwoven 
fabric due to the flotation of the tape provided by the air bearing guide 
and the attracting effect cause by the magnetic force of the permanent 
magnet. Accordingly, with the invention magnetic tapes of good reliability 
can be manufactured without the occurrence of problems such as drop-out 
due to shedding of magnetic powder or tape base material from the tape 
edges in the cutting process, or tape edge problems caused by the cleaning 
apparatus.