US3025017A

US3025017A - Device for a winding mechanism for record tapes

Info

Publication number: US3025017A
Application number: US5876A
Authority: US
Inventors: Wahlstrom Sven Erik
Original assignee: Atvidabergs Industrier AB
Current assignee: Atvidabergs Industrier AB
Priority date: 1959-02-13
Filing date: 1960-02-01
Publication date: 1962-03-13
Anticipated expiration: 1979-03-13
Also published as: GB906351A; DE1248724B

Description

March 13, 1962 s. E. WAHLSTRiD'M 3,025,017

DEVICE FOR A WINDING MECHANISM FOR RECORD TAPES Filed Feb. 1, 1960 3 Sheets-Sheet 1 March 13, 1962 s. E. WAHLSTRCM DEVICE FOR A WINDING MECHANISM FOR RECORD TAPES Filed Feb. 1, 1960 3 Sheets-Sheet 2 1/ ill 3 .F' I r w w w m m 0 W m 2 M 1 2 M 6 W0 w (m D 3 2 A. m 3 H 9 N /A in \2 7m M a J V 1 A w a 2 Q a w I II @J M E I- .I f A O 0 E L. 1 \g w: 2 1 L U March 13, 1962 s. E. WAHLSTRC-JM DEVICE FOR A WINDING MECHANISM FOR RECORD TAPES 3 Sheets-Sheet 3 Filed Feb. 1, 1960 SOLENOID IL United States Patent Ofiice 3,025,017 Patented Mar. 13, 1952 3,025,017 DEVICE FOR A WlNDlNG MECHANISM FOR RECORD TAPES Sven Erik Wahistriim, Enslrede, Sweden, assignor to Aktiebolagct Atvidabergs Industrier, Atvidaberg, Sweden,

a joint-stock company of Sweden Filed Feb. 1, 1960, Ser. No. 5,876 Claims priority, application Sweden Feb. 13, 1959 2 Claims. (Cl. 242-75.3)

This invention relates to a device for a winding mechanism for record tapes comprising a loop forming device for the formation of loops in the tape to take up tensions caused by the acceleration of the tape, and a movable means adapted, via a resilient intermediate member to pull the loop forming device into a position for forming at least one loop in the tape, said resilient intermediate member being dimensioned in such a manner that the loop forming device is returned to its home position as the tension in the tape increases.

It is a primary object of the invention to render possible a very rapid acceleration of a recording tape and of a coil on which a longer or shorter portion of the tape is wound, without causing too great tensions in the tape.

Such an acceleration is required for example for recording or sensing purposes in connection with the socalled start-stop method according to which the tape is moved stepwise, or in cases when the tape feeding is commenced by one tape drive means and continued by another drive means.

Said object is achieved by the device according to the invention which is substantially characterized in that the loop forming device is connected with a preferably adjustable, one-way acting damping device which becomes operative first after said movable means has been moved to the position where iti s pulling the loop forming device into its loop forming position and which is active only during the return motion of the loop forming device as the loops are straightened out.

The tape length required for the formation of the loops is preferably as great as or greater than the tape length wound oif or on during a complete acceleration process covering the period from the standstill of the coil to its full velocity so that during the acceleration process the tension of the tape will be the smallest possible.

In the accompanying drawings an embodiment of the invention is illustrated in schematic manner by way of an example showing the invention applied to a storage device.

FIG. 1 is a side view of a storage device showing the loop forming device and a damping device, the latter being of the pneumatic type. FIG. 2 shows the loop forming device and the clamping device in a position occupied by said devices during a later phase of the operation, and illustrates (in schematic manner and on a reduced scale) further details of the storage device.

FIG. 3 is a side view corresponding to FIG. 2 showing the loop forming device and the damping device in winding position of the coil.

FIG. 4 is a longitudinal section of the damping device on an enlarged scale.

FIG. 1 shows a coil 1 from which a record tape 2 i is unwound. In the phase shown the unwinding operation is eiiected partially by a weight 3 fastened to the end of the coil and under the influence of gravity mov ing downwards in a track 4, and partially by an electrornotor (not shown) coupled to the shaft 5 of the coil 1. The loop forming device designated in its entirety by 7 is provided on the side of said track 4 very close to the upper end of the track and is located right in front of the damping device designated in its entirety by 8, provided on the opposite side of the track 4. The clamping device ti appears more clearly in FIG. 4. Directly beneath the aforementioned members a magnetic head 9 is provided (shown schematically in H63. 2 and 3) which constitutes the recording and sensing means and with which a tape supporting member 10 cooperates. A capstan 11, and in cooperation therewith a pressure roller 12, is arranged below the magnetic head 9 and the tape supporting member 10 on opposite sides of the track 4 in such a manner that by action of a solenoid 14 (shown schematically) the pressure roller 12 can be advanced to press the tape 2 against the continuously rotating capstan 11 so that the tape is unwound at a high velocity past the magnetic head 9. A fork 15 with two prongs is provided below the

rollers

11 and 12 to embrace the opposite edges of the tape and in active posiion to engage with recesses 16 in the one wall of the track 4 thereby preventing the weight 3 from being pulled upwards past the fork 15 when, in connection with the change of the drive means from the motor (not shown) to the tape drive means 11-12 for unwinding the tape, the loop forming device 7 is turned from the position according to FIG. 1 into the position according to FIG. 2. At the bottom of the FIGS. 2 and 3 is shown a light source 17 and a photo-cell 1% located on opposite sides of the track 4 and forming together an optical indicator by means of which the aforementioned change of the tape drive means is initiated when "the path of the light beams from the light source 17 to the photo-cell 18 is interrupted by the weight 3.

The loop forming device 7 comprises a crank having two slightly

curved legs

20, 21 which at their ends are provided with

rotatable tape rollers

22 and 23 respectively. The loop forming device and an arm 25 rigidly connected therewith are fastened on a pivot axis 24. In non-operative position (FIG. 2) the loop forming device in its entirety is located on the side of the track 4. The

legs

20, 21 with their rollers 22, 2.3 can be pivoted into the spaces between three tape guiding members having the form of

rollers

27, 28, 29 which are arranged on the side of the track 4 opposite to the side on which the pivot axis 24 of the loop forming device 7 is located, so that two loops are formed in the tape when the loop forming device is pivoted from the position according to FIG. 1 into the position according to FIG. 2.

The arm 25 carries a pivotal piston rod 30 to which is secured a piston 31 movable in a cylinder 32 having one substantially open and one substantially closed end, both the piston 31 and the cylinder 32 constituting a part of the damping device 7 which is more clearly illustrated in FIG. 4. The piston 31 is a thin disc cut from a sphere having its edges curved in such a manner, that in all directions their radius of curvature (that is the radius of the sphere from which the disc is cut out) is like the radius of the cylinder 32, causing the piston 31 to abut tightly to the cylinder wall even if owing to the pivotal motion of the loop forming device 7 the piston rod 30 forms an angle with the cylinder axis. The curvature of the edge of the piston 31 is however, exaggerated in the sectional view of FIG. 4. A plurality of perforations 33 disposed in the piston 31 are covered by a diaphragm 34, for example of plastic, attached to the piston 31 on the side facing the open end of the cylinder 32. Said perforations 33 and said diaphragm 34 form a check valve designed to seal when the piston 31 moves to the left in FIG. 4 and to open when the piston moves to the right. The substantially closed end 36 of the cylinder 32 is provided with an adjustable throttle valve 37 to control the velocity of the air flowing into the cylinder portion located between the piston 31 and said end 36. The substantially closed end 36 is further provided with an air outlet channel 38 which cooperates with a movable sealing plug 39 (FIGS. 1-3) fastened by means of a rectangular flat iron 40 or the like to an angle bar 41, one flange of which is partially cut away. One end of a tension spring 43 is fastened on said angle bar 41 by a pin 42 while the other end of the spring is fastened on a journal 45 fixed on the arm 25 of the loop forming device 7. When the tape 2 is substantially without tension, the journal 45, by action of the tension spring 43, abuts a stop face 46 on said flange of the angle bar 41 which is partially cut away, said angle bar 41 being fastened to a flat iron 47 (FIG. 1) which is rigidly connected with a control carriage (not shown). A preferably resilient stop member 48 which is fastened to the flat iron 47 and the angle bar 41 serves in cooperation with the journal 45 as a stopper to limit the counterclockwise pivotal motion of the loop forming device 7. The journal 45 abuts against said stopper 48 as shown in FIG. 3. Owing to the fact that the tape supporting member and the fork also are rigidly connected with the carriage, the sealing plug 39 is moved to the opening of the air outlet channel 38 and the loop forming device 7 is pivoted by means of the resilient connection 4741-42--43--45- 7 from the position according to FIG. 1 into the position according to FIG. 2, the piston rod 31} and the piston 31 at the same time being moved to the right, all this occurring immediately after the engagement of the fork 15 with the recesses 16 and after the tape supporting member 10 has moved the tape 2 towards the magnetic head 9.

When during the first phase of the unwinding operation which is effected by the weight 3 and by the motor coupled to the shaft 5 of the coil 1, the weight 3 interrupts the light beams from the light source 17, the motor is stopped and the control carriage is moved to its right end position. Hereby the fork 15 is caused to engage with the recesses 16 in order to prevent the loop forming device 7 during its immediately subsequent clockwise pivotal motion around the pivot axis 24 lifting the weight 3, and the tape supporting member 10 is moved towards the magnetic head 9.

The carriage having reached its right end position, the motor is substantially stopped but the coil is turned slightly further owing to the inertia and the unwinding action of the loop forming device 7 caused by the fact that the Weight 3 is retained by the fork 15.

The second phase of the unwinding operation is commenced by energizing the solenoid 14 causing the pressure roller 12 to press the tape 2 against the capstan 11 by which from that moment the unwinding operation is taken over. The primary object of the loop forming device 7 in this connection is to decrease the tension caused in the tape 2 during the subsequent acceleration process. Said object is attained in that the loop forming device, owing to the tension of the tape, is turned in a counterclockwise direction from the position according to FIG. 2 into the position shown in FIG. 3. During this pivotal motion, the piston rod 30 and the piston 31 are moved to the left by arm 25 until this motion is braked by the outside air pressure against the left side of the piston 31. During the relatively fast first phase of said motion, the loops are more or less shortened without causing the coil 1 to accelerate considerably, the velocity of the loop forming device 7 and of the piston 31 and the resistance of the clamping device decreasing according to the acceleration of the coil. To keep the tension of the tape below an acceptable value, it is necessary to use, during the acceleration process, the full length of the tape portion taken up by the loop forming device. This means that the loops must have a total length which is at least as long as the tape portion advanced during the acceleration process, covering the period from the tape in standstill position to full velocity of the coil 1.

The circumferential velocity of the capstan 11 is, in the embodiment described, 5 meters per second which is substantially more than the maximum velocity of the 4 tape during the phase of the unwinding operation described above. Therefore the coil 1, which is substantially standing still at the moment when the pressure roller 12 is beginning to force the tape 2 towards the capstan 11, is given a kinetic energy corresponding to the tape velocity 5 meters per second, that is of the magnitude one kilogram-centimeter, without exceeding the allowable maximum tension in the tape, in this case 0.3 kilogram. This is realized by means of the loop forming device 7 which in the embodiment shown forms two loops, i.e. four parts in the tape 2 causing the tension of the tape to be reduced substantially to one quarter compared with a straight tape. The loop forming device must take up a tape length of about 3-4 centimeters to be able to supply said kinetic energy at a tension of 0.3 kilogram, but owing to other circumstances explained below the loop forming device is designed to take up a total tape length of about 10 centimeters.

However, not only the coil 1 but also the loop forming device 7 must be accelerated and thus the mass of the latter must be as small as possible.

The loop forming device described has many advantages when the analyzing and recording operations are carried out according to the so-called start-stop method comprising the steps of seeking out successively addresses on the tape which are located at an increasing distance from the tape end fastened to the coil, in order to commence the sensing or recording operation in these addresses, the tape being stopped after each sensing or recording operation and thereafter started again, for instance after that the partial information received is processed. When it is intended to stop the tape after the aforedescribed acceleration process, a signal is received When a given point on the tape is sensed, said point varying from one case to another (usually'being the last symbol of the recording block in question). Owing to said signal, the current supply to the solenoid 14 is interrupted, causing the pressure roller 12 to be pulled away from the capstan 11 so that in spite of the fact that the capstan continues to rotate, the unwinding operation of the tape does not continue. Moreover, owing to the fact that by said signal the shaft 5 of the coil 1 is also stopped, the coil comes to a standstill. The tension of the tape 2 is therefore eliminated, and the relatively weak spring 43 pulls the loop forming device 7 in clockwise direction from its position according to FIG. 3 to the position shown in FIG. 2. The coil 1 being in arrested position, the loop forming device 7 draws the tape portion which is located below the loop forming device upwards past the magnetic head 9, the pivotal motion of the loop forming device being accelerated by means of the check valve 33-34 which opens as the piston moves to the right. Owing to the inertia of the drive mechanism 1112 and to the necessary braking time of the coil 1, there will be a certain retardation or stopping distance of the tape (measured from the magnetic head 9 downwards) from the instant when the stop impulse was given to the instant when the tape velocity directly in front of the magnetic head 9 is zero. If thereafter a starting impulse is given, the solenoid 14 is supplied with current causing the pressure roller 12 to be advanced to press the tape against the capstan 11 whereafter the tape is accelerated, while at the same time the loops formed by the loop forming device 7 are straightened out until the state shown in FIG. 3 is restored.

During the period from the starting impulse to the moment when the tape has reached full speed directly in front of the magnetic head 9 so that the recording and sensing operation can take place, a certain tape length can pass the magnetic head. In order to ensure the best possible utilization of the tape and to prevent the loss of any information recorded on the tape, the loops formed by the loop forming device 7 must have a total length which is at least equal to the sum of the maximum tape length which during a complete retardation process covering the period from normal tape velocity to its stop is fed past the magnetic head 9, and of the maximum tape length which during a complete acceleration process consecutive to the retardation process and covering the period from the stop of the tape to its normal velocity is fed past the magnetic head 9 (the tape velocity being measured in a point right in front of the magnetic head). The reason why the loop forming device is dimensioned for such a great tape length as 10 centimeters at a tension of 0.3 kilogram, is to be seen in the fact that after almost all of the tape is unwound, the velocity of the coil 1 is very high, because the diameter of the coil has decreased considerably and the circumferential velocity of the capstan 11 is constantv Said high velocity corresponds to a great kinetic energy of about 3 kilogram-centimeters which must be supplied to the coil in the start-stop method while the loops formed by the loop forming device are straightened out and without exceeding the tension of 0.3 kilogram in the tape. The embodiment described and shown in the drawings is only to be considered as a nonlimiting example the details of which can be modified in various ways within the scope of the following claims. For example, the substantially pneumatic clamping device can be replaced by a spring system or by another similar device. However, resilient damping means are less suitable than substantially inelastic damping means, because the acceleration occurs more uniformly with the latter type of damping means and the tape is sensed more smoothly, while with resilient damping means each return motion of the loop form-ing device 7 to the position according to FIG. 1 occurs with a jerk. Moreover, when a loop forming device is actuated by an elastic clamping device, there will be the risk that said loop forming device when it is moved from its position according to FIG. 2 into the position according to FIG. 3 will be swung back into the direction of its starting position, whereby the coil 1 receives an additional rotary impulse or after-touch causing the tape 2 to become disordered on the coil.

What I claim is:

l. A take up device for a winding mechanism for recording tapes on a recording machine provided with a tape supply coil and a recording head, said device compris ing a loop forming device for the formation of loops in the tape to take up tensions caused by the acceleration of the tape, a movable means adapted to pull the loop forming device into a position for forming at least one loop in the tape, a resilient member between said loop forming device and said movable means, said resilient member being so dimensioned that the loop forming device may return to its home position as the tension of the tape increases, an adjustable, one-way acting pneumatic damping device comprising a fixed cylinder with one substantially open and one substantially closed end and a movable piston connected to said loop forming device adapted to move towards the open end of the cylinder as the loops are straightened, said damping device being provided with a check valve closing as the piston moves in said direction but opening as the piston moves in the opposite direction, an adjustable throttle valve, a sealable air outlet channel in said substantially closed end, and a sealing plug mechanically connected with said movable means and adapted to move into sealing position with respect to said outlet channel at the same time as said movable means pulls the loop forming device into operative position.

2. The device of claim 1, in which said loop forming device carries said tape between said tape supply coil and said recording head and in which, upon stopping of movement of the tape through the recording machine, the loop forming device pulls tape back that has progressed past said loop forming device to form part of said loop whereby upon starting said tape again, said tape again passes said recording head.

References Cited in the file of this patent UNITED STATES PATENTS 1,539,408 Pigeon May 26, 1925 2,006,628 Cline July 2, 1935 FOREIGN PATENTS 722,400 France Dec. 29, 1931