GB1014551A - Improvements in and relating to magnetic sound recording and reproducing heads - Google Patents

Abstract

1,014,551. Magnetic recording, playback and erase heads. B.S.R. Ltd. Jan. 9, 1964 [Jan. 16, 1963], No. 1922/63. Heading G5R. A combination head comprises separate erase and record/playback electromagnets mounted in a common container and each comprising a laminated core in the form of an elongate loop with the polepieces at one end, the loop comprising two parallel limbs of which one extends linearly to its polepiece and, at the end of the loop, the other is off-set towards the linearly extending limb to bring the polepieces together, a bobbin assembly being provided on at least one of the limbs of each core. Referring to Fig. 3 the erase magnetic core 23 comprises a bundle of parallel laminations bent into a loop formed with pole-pieces 13 and 14; one limb is surrounded by a coil 28 on a former 29, the two ends of the coil and a centre tap being connected to terminals 4. The record/ playback core is similar but has coils 35 and 36 wound on formers 37 and 38 surrounding each limb; the coils are connected in series and the junction and the other two ends are connected to terminals 4. Thus the signal to be recorded can be supplied to one of the coils, which has a low impedance, whereas both coils in series may be used for playback. The polepieces extend through a disc like insert 12, of non-magnetic alloy, set in U-shaped body 5 bolted to a can 1, the body 5 and the can 1 being of high permeability low-loss magnetic alloy and serving as a magnetic screening enclosure. As shown in Fig. 7 the erase polepieces 50 may be wider, transverse to the tape, than the record/playback polepieces 51, and the polepieces may be offset with respect to the centre lines of heads 48 and 49 so that each head can support a tape over its whole width whilst operating on only one of four tracks on the tape. In the arrangement shown the two heads operate on tracks t1 and t3 and when the tape is reversed tracks t4 and t3 will be similarly engaged. The erase polepieces may be constructed as described in Specification 934,898.