Patent GB-1489669-A (GB)
Title: Magnetic tape recording apparatus
IPC: G11B15/28
Filed: 1975-09-30
Abstract: 1489669 Magnetic tape recorders UHER WERKE MœNCHEN GmbH 30 Sept 1975 39980/75 Heading G5R [Also in Division G3] A magnetic tape recorder, e.g. for sound, comprises two tape spool drive motors (51), (52), Fig. 5 (not shown), a motor for rotating a capstan 13, Fig. 3, for transporting the tape 1 without the use of a pressure roller, brakes 27, 28 for tape spool supports 64, 65, and tape guides 5, 13a, 16, 20, 21, 49, 50 movable by a motor (56), Fig. 3, via members 4, 9, 11, 14, 17 between a first operating position, Fig. 4 (not shown), in which the tape can be stopped and rapidly wound forward and in reverse rectilinearly past magnetic heads 78, 46, 47, 53 and capstan 13 without contact with the heads and capstan, and a second operating position, Fig. 3, in which the tape is guided by the guides and lies against the heads and is drivingly engaged with the capstan 13, the motor (56) operating via a control member 32 to release the brake 28 of one of the spool supports 65 during the movement of the tape guides between their two operating positions. In the fast wind/rewind position, Fig. 4, the tape is engaged by a pin 5 on lever 4, by a pin 16 on lever 14 and by a pin 20 on lever 17. In the recording and playback position, Fig. 3, the tape is engaged by a roller 12a on a lever 11 engaged via pin 10 with lever 4, by a pin 50 and a roller 49, which co-operate to wrap the tape in a U-shape about capstan 13 with the capstan engaging the backing side of the tape, and by a pin 21 on lever 17. To change between the two positions a geared motor (56), having a shaft 58, rotates a disc 9 about capstan 13, the disc 9 carrying pin 50, which has a base part engageable with lever 14 to pivot the latter, and roller 49 and having a cam surface 8 engaged by followers 7, 19 on levers 4, 17 respectively. Shaft 58 also drives a can disc 22 engaged by a lever 32 operable to release brake 24, 28 during the change over so that a length of tape to form the loop around the capstan can be drawn from and wound on to the take-up spool (3), Fig. 1 (not shown), brake 24, 28 only being so disengaged during the actual change over and not at the start/end. A solenoid 29 is operable to disengage both brakes. The capstan 13 has a smooth, hard friction coating (126), Fig. 11 (not shown), e.g. of polyurethane, with a ground surface. A sub-assembly (43), Figs. 1, 2 (not shown), carrying press keys (42), volume &c. controls (66), (68), and electronic circuits is pivotable upwardly at a side hinge (44) to facilitate servicing. A tape counter 70, Fig. 3, belt-driven from spool motor (52), has a press-button switch 132 which when operated holds the counter at zero, even when the tape is being driven, and also disables a stop operation normally effected by a conductive film at the beginning of the tape. Tape tension is controlled by adjusting the torques of the spool motors (51), (52) by respective tension controlling and setting devices 82, 83, Figs. 3, 7, having tape guide rollers 35, 99. The roller of each such device is mounted at a free end of a shaft 96, the other end of which is fixed so that tape tension variations bend shaft 96 to vary the position of a shield 98 in a light beam extending between a source (112) and a phototransistor (111), Fig. 10 (not shown), of a photoelectric transducer 95, Fig. 7, the phototransistor (111) being in a circuit controlling the energization of spool motor (51) or (52). This circuit operates to maintain constant tension despite changes in the tape coil diameter on the corresponding spool and also compensates for mechanical oscillations. The required tension is set by screwdriver adjustment of a shaft 94a, Fig. 7, carrying a worm gear 91 meshed with a gear 90 on a pin 90a threaded in a movable carriage 86 on which the photoelectric transducer 95 is fixed. Deflection of the shafts 96 of devices 82, 83 may alternatively be sensed by capacitive, electromagnetic or pieozelectric transducers. The pins 20, 21 on lever 17, Fig. 3, are arranged so that the tape reaches roller 35 of device 82 from capstan 13 at the same angle in both positions of the tape guides.