Method of tensioning a tape

A tape of a tape-recording device passes between a braking roller, a first sound shaft, a second sound shaft, and a pulling roller located one after the other. The pulling forces of the rollers and the slips of the tape of the sound shafts are adjusted so that the pulling force of the tape between the braking roller and the first sound shaft and the pulling force of the tape between the first and second sound shafts are directed toward the braking roller whereas the pulling force of the tape between the second sound shaft and the pulling roller changes the direction to the opposite and is smaller than the pulling force of the tape between the first and second sound shafts.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of and an arrangement for 
attaining a tape-protective tensioning of a tape in tape-recording 
devices. More particularly, it relates to a method of and an arrangement 
for tensioning a tape in a tape-recording device with a braking roller, a 
pulling roller, two sound shafts rotating with approximately equal angular 
speed, and at least one sound head. 
Known tape-recording devices encounter the problem in that they must 
provide for a firmest possible abutment of the sound tape against the 
sound head in order to eliminate undesirable variations of amplitude 
during recording and reproduction, particularly when separate head systems 
for recording and reproduction are utilized in cassette devices. This 
problem particularly arises when two sound shafts are utilized, in order 
to attain the sufficient tape-head contact. In such a device contrary to 
the device with only one sound shaft, the driving force is indetermined 
statically. In addition, when the fixed axis of rotation normal to the 
tape plane extends downwardly of the tape toward the sound shaft, the tape 
drive is mechanically instable, inasmuch as even small deflections of the 
sound tape parallel to the sound shaft are automatically increased. When 
the fixed axis of rotation normal to the tape plane extends upwardly of 
the sound tape, deflections of the sound tape parallel to the axis of the 
sound shaft are automatically compensated. Pulled sound shafts are 
mechanically instable, and driven sound shafts have a stable tape position 
(RADIO MENTOR ELECTRONIC, 11/78-198). 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a method 
of and arrangement for tensioning a tape in a tape-recording device, in 
accordance with which, two sound shafts are provided and guarantee a 
mechanically stable position of a sound tape. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a method of tensioning of a tape of a tape recording device including a 
braking roller, a pulling roller, and two sound rollers located 
therebetween, in accordance with which method the pulling forces of the 
rollers and the slip of the tape on the sound shafts are so adjusted that 
the pulling force of the tape upstream and downstream of the sound shafts 
following the braking roller is directed toward the latter, whereas the 
pulling force changes its direction on the second sound shaft. 
In accordance with another feature of the present invention an arrangement 
for tensioning a tape in a tape-recording device is provided in which the 
pulling forces of the rollers and the slips of the sound shafts are also 
adjusted so as to attain the above-mentioned relation between the pulling 
forces of the tape. 
When the method is performed and the arrangement is designed in accordance 
with the applicant's invention, both sound shafts no more drive the sound 
tape, inasmuch as both sound shafts must overcome a force which acts in 
the direction opposite to the running direction of the sound tape, whereby 
by both sound shafts stable tape positions are attained. The loading of 
the edges of the tape by guiding means is thereby neglectibly small and 
therefore a tape protection is attained. The passage of the pulling force 
of the tape through the first sound shaft toward the tape portion located 
between the first and the second sound shafts (counted from the braking 
roller) can be adjusted by the pressure of the first pressure roller, 
therefore, by the slip. It is however, not greater than in the 
arrangements in which the tensioning of the tape between the sound shafts 
is determined by adjustment of the force originated from the pulling 
roller. 
In accordance with a further feature of the present invention, the braking 
roller, the pulling roller and the first and second sound shafts are 
reversible so that the functions of the drive elements can be reversed. In 
this case the operation of the arrangement corresponds to the 
"autoreverse" operation in which the braking roller serves as the pulling 
roller, the first sound shaft serves as the second sound shaft, and the 
second shaft serves as the first sound shaft. In such a construction, 
immediately after reaching of the tape end, the direction of functioning 
is reversed and the tape is switched to the second sound track so that the 
playing of the second sound track can immediately start. In accordance 
with the invention, such operation is also performed with stable run of 
the tape. In order to attain this, the braking roller must provide for the 
same pulling force of the tape as the roller which now works as the 
pulling roller and which has worked before as the braking roller. This can 
be attained by provision of mechanical or electrical tape brakes, however, 
the above-mentioned results can be provided easier with the aid of the 
electrical tape brakes. In this case the pressure of both pressure rollers 
must be the same, or measures must be taken which provide for the reverse 
of the pressure force of the pressure rollers. 
In accordance with a further advantageous feature of the present invention, 
the sound shafts rotate in synchronism with each other. This can be 
attained in the case when they are driven by the common drive means. A 
stable run of the tape was not possible in this case in the known 
arrangements and methods. 
Especially high tape protection and uniform run of the tape is attained 
when the forces are symmetrical relative to the second sound shaft, since 
no slip is possible in this case on the second sound shaft. Such a fine 
determination of the pulling force of the tape is possible especially in 
electrically controllable pulling roller and braking roller. 
It is also possible that further sound shafts are provided between the 
first and the second sound shafts, and the pulling force of the tape 
upstream and downstream of the further sound shafts is directed toward the 
braking roller. Thereby a stable tape run can be attained also in 
completely overdetermined systems. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
An arrangement for tensioning a tape in a tape-recording device is shown 
schematically in the drawing and has a braking roller 10 from which a 
sound tape 40 runs and is braked with a pulling force 100 of for example 
20 p (pond) on a sound shaft 11. The sound shaft 11 together with a 
pressure roller 12 displaces the sound tape in the direction 103 toward a 
sound head 30. A slip takes place between the sound shaft 11 and the 
pressure roller 12, the slip relatively too slowly displacing the sound 
tape 40. 
A sound shaft 21 is further provided. The sound shaft 21 is driven by the 
same drive means by which the sound shaft 11 is driven. This can be done 
for example by a common belt which drives both sound shafts in rotation. 
When the sound shafts 21 and 11 are driven by the same drive means, the 
sound tape 40 obtains a pulling force which is directed in the direction 
101 and provides well abutment of the sound tape 40 against the sound 
head. 
On the other hand, the pulling force 101 which is caused by the "passage" 
of the force 100 over the drive point 11-12, cannot lead to slip of the 
sound shaft 11 and thereby inherently unstable run of the tape over the 
sound shaft 11. The pulling force 101 can be equal, for example, to 2 p. 
However, the sound shaft 21 retains the ability to pull the sound tape 40 
and thereby to provide the inherent stability of the tape run. 
A pulling roller 20 is further provided after the sound shaft 21. The 
pulling roller is so adjusted that a pulling force 102 acts over the 
pressure roller in the direction opposite to the running direction of the 
tape. The pulling force 102 may be smaller than the pulling force 101. In 
this case, the sound shaft 21 has the ability to apply a transporting 
pulling force to the sound tape 40. In this case, a change of sense of the 
pulling force on the sound shaft 21 takes place, whereby the sound tape 
behind the sound shaft 21 remains tensioned. The advantageous condition is 
attained when the pulling forces 101 and 102 are of equal magnitudes, 
inasmuch as no slip takes place over the sound shaft, despite the fact 
that both sound shafts 11 and 21 simultaneously apply a pulling force to 
the tape, the inherently stable tape run takes place, and the tape over 
its entire length remains tensioned with well abutment against the sound 
head 30. 
A so-called "auto-reverse" operation can be attained when the braking 
roller 10 serves as a pulling roller, and the pulling roller 20 serves as 
a braking roller. The pulling force 100 must be applied from the new 
braking roller 20, and the pulling force 102 must be applied from the new 
pulling roller 10. The pulling force 101 changes its direction, when the 
passage of the braking force 100 through the pair 21-22 have the same 
magnitude as the passage through the pair 11-12, when in condition of 
identical outer surface properties both pairs exerts identical pressure. 
An additional such pair may be provided between the sound shafts 11 and 21. 
In this case it is necessary to adjust the slip of all sound shafts so as 
to attain the passage of the braking force to the portion of the tape 
located behind a respective sound shaft, in order to provide for a pulling 
force in the tape in direction toward the braking roller. The pulling 
force of the tape must change its direction on the sound shaft which is 
located adjacent to the pulling roller so as to attain a sense variation. 
The passage is also adjusted here by slip and pressure, and in the case of 
the auto-reverse operation is identical for all sound shafts. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
method of and an arrangement for tensioning a tape in a tape-recording 
device, it is not intended to be limited to the details shown, since 
various modifications and structural changes may be made without departing 
in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.