| 摘要 |
853,209. Driving sound film or tape. AMPEX CORPORATION. Jan. 27, 1958 [Jan. 28, 1957], No. 2699/58. Class 40 (2). In a magnetic tape apparatus means are provided to maintain constant tape tension between the supply reel and the capstan. Fig. 1 shows the feed spool 16 from which the tape 19 passes over a guide roller 47 fixed to the tape deck, round a roller 46 carried on the free end of a tensioning arm 18, to an idler roller 23 and then via a second tensioning arm and guide roller to the take-up spool 15. Between the limbs 31 of the loop of tape passing over the idler roller is a drive capstan 22 on to which the tape is pressed by two rollers 32. Magnetic heads 45 contact the tape between the idler roller 23 and capstan 22. A magnetic shielding fin 30 extends from the idler wheel 23 to a guide stud 30b. The tape tensioning means comprises a brake drum 50 (see Fig. 2), attached to the shaft 51 of the associated turntable and engaged by a band brake 52, one end of which is attached at 54 to a plate 56 which is pivoted at 60. The plate is acted on by a spring 62 which tends to apply the brake and in the opposite direction by the spring 59 connected between the plate 56 and an extension 58 of the arm 18. The other end of the brake band is connected to a bar 64 which is connected at one end to a spring 66 and at the other end to a member 69 connected by the pins 68 to a pair of rotarytype solenoids 67 which when energized move the bar 64 sufficiently to completely release the brake. The arm 18 and the brake band 52 pass through notches cut in the bar 64. During clockwise rotation of the drum 50 the braking force is determined by the initial tension in the spring 62 and is modified by the movement of the arm 18 as the tape tension increases or decreases. Increasing tension causes rotation of the arm clockwise as seen in Fig. 2 so that the side of the arm engages the bar 64 and moves it to the left against the spring 66. This movement reduces the braking force by moving the end of the brake band attached to the bar 64 away from the drum, and by increasing the tension in the spring 59 reduces the effective tension of the spring 62. Clockwise movement of the arm is limited by the dash-pot 76. Rotation of the drum in a counter-clockwise direction causes the plate 56 to move against the stop 63, so that the brake tension is controlled solely by the tension of spring 66. During fast forward or rewind operations both brakes are released and the necessary tape tension is maintained by supplying a reverse electrical torque to the feed spool. |
