Patent GB-1007455-A (GB)
Title: Magnetic tape equipment having a buffering device
IPC: H02P5/48
Filed: 1962-05-02
Abstract: 1,007,455. Feeding record tapes. TELE FUNKEN PATENTVERWALTUNGSG.m.b.H. May 2, 1962 [June 14, 1961], No. 16838/62. Heading G5R. [Also in Division G3] In an arrangement for passing a magnetic tape reversibly between storage reels, which may be selectively driven, allowed to idle, or braked, a symmetrical arrangement of vacuum storage columns are arranged about a magnetic head arrangement 2 across which the tape is fed by pressure rollers 4l. 4r, selectively coacting with oppositely rotating capstans 31, 3r. For the left-hand side, a reel 5 is arranged through a combined brake and clutch K to be driven by a motor M by the energization of a winding wa, to be braked by a winding wb, or to idle. The tape 1 passes over a roller 6 into a vacuum column 7, wherein is formed a loop 1b and from there over a roller 8 to the magnetic head arrangement 2. The roller 6 and pressure rollers 4l, 4r drive frequency generators 13, 141, 14r respectively which through trigger circuits ST1, ST2 pulse a pair of flip-flops FF1, FF2 coupled by blocking circuits SP1, SP2 to derive binary outputs to AND gates U1, U2 indicative of whether the speed of the tape past the head is greater or lower than the speed of take-up or feed from the reel 5. The position of the loop 1b is sensed by transistorized Schmitt trigger circuits ST3-ST5, incorporating photo-transistors, the desired position of the loop being adjacent to the light path to trigger circuit ST4. The output from trigger circuit ST4 is fed directly to AND gates U4, U6 and through an inverter 12 to AND gates U5, U7. The gates U4-U7 are enabled for the appropriate direction of tape travel by signals from a bi-stable flip-flop RL. Gates U4, U5 control an OR gate 02 connected to inputs of the gates U2, U3 controlling through an OR gate O1 a winding wb of the brake, and gates U6, U7 are connected through an OR gate 03 to an AND gate U1 controlling the winding wa for the clutch. The selective energization of the windings wa, wb through the logic circuits is arranged to control the braking, driving, or idling of the reel in dependence on the loop position relative to the light beam to the trigger circuit ST4, on whether the loop is increasing or decreasing in size as determined from generators 13, 141, 14r, and on the direction of travel of the tape as indicated by the bi-stable circuit RL. A decrease or increase of the loop beyond permissible limits is sensed by trigger circuits ST3, ST4 and loss of vacuum is sensed by a pressure-responsive device W which through an OR gate 04 energize the brake winding wb. The absence of a fault provides a signal from the OR gate 04 which through an inverter 13, enables the gate U1 and provides a checking signal to an output U. During starting, since the outputs of generators 13, 14l, 14r are of low frequency, both inputs of the flip-flop FF2 are fed from a multivibrator MV controlled by a discriminator LH having an output when the tape-drive is running such that the gate U1 is pulsed intermittently so that the reel drive is reduced during the acceleration phase. When the loop increases to obscure the light beam to trigger circuit ST4 the brake is applied to stabilize the loop length.