Patent GB-679085-A (GB)
Title: Erasure means for magnetic recording devices
IPC: G11B5/004
Filed: 1951-02-13
Abstract: 679,085. Magnetic recording apparatus. BRUSH DEVELOPMENT CO. Feb. 13, 1951. [July 17, 1950] No. 3479/51. Class 40 (ii). In a magnetic recording device having a rotatable record member 10 with a plurality of tracks thereon, means are provided to condition the device for recording in which erazure of all the said tracks during a single rotation of the said record is first carried out and thereafter a recording head 13 is caused to traverse said record tracks. When a record switch 72, Fig. 5, is closed, a record relay 69 is energized which thereby energizes a play relay 70 via begin switch 64 and a pair of contacts of record relay 69, and closes the circuit of the motor M which thereupon rotates the record 10 by means of shaft 9<SP>1</SP> and a jockey pulley 11. At the same time, the energizing of record relay 69 energizes record solenoid 47 through pairs of contacts on record relay 69 and play relay 70. The energizing of record solenoid 47, Fig. 2, moves a system of members 46, 45, 44 and 43 so that a bellcrank 40 is moved clockwise by an inclined surface on the member 43 engaging a pin 48 on the said bellcrank 40. The opposite end of the bellcrank 40 from the pin 48 is thus moved downwardly from between a spring 34 and a cam 33 whereby clutching engagement is effected between cam 33 and a gearwheel 27 driven clockwise by a gearwheel 26 revolving counterclockwise with the record 10. The endwise movement of the member 43 is sufficient for the pin 48 to drop behind the sloping surface on member 43 as the cam 33 rotates, so that the bellcrank 40 returns to its normal position. During subsequent withdrawal of the member 43 the sloping surface rides freely back over the pin 48. Rotation of the cam 33 lifts a lever 36 which lowers arms 30 and magnets 29 on to the surface of the record 10 to eraze a previous recording. At an appropriate moment in the rotation of the record 10, when the erazed area of the record reaches the vicinity of the recording head 13, contacts 66, 67, Figs. 4 and 5, are closed for a short period so that a play solenoid 50 is energized via a pair of contacts on play relay 70, and continues to be energized by the closing of its own pair of contacts before the contacts 66, 67 have opened again. Play solenoid 50 moves a link 51 coupled to a slotted bar 52 so that an arm 53 slidably connected thereto by a pin 53<SP>1</SP> and carrying the transducer 13 and a half-nut 54, is moved into an operative position in which the transducer 13 contacts the record 10 and the half-nut 54 engages a leadscrew 25 driven by a gearwheel 28 from gearwheel 27. When the arm 53 is moved to the operative position, begin switch 64, Fig. 3, is opened, but circuit through play relay 70 is maintained through end switch 61 and two pairs of its own contacts. At the completion of one revolution of the cam 33, the cam follower 35 enters a depression in the cam 33 so that the erazing magnets 29 are lifted, and the bellcrank 40 enters again between the spring 34 and the cam 33 so that rotation of the latter is stopped. As the recording proceeds a stop member 49 is pushed along a serrated bar 56 against the tension of a spring 59, Fig. 3, the stop member 49 being held away from the teeth of the bar 56 by pressure of the member 45 under the influence of solenoid 47. When the recording is finished, record switch 72 is opened and all relays and solenoids become de-energized, so that bar 45 moves away from the stop member 49 which thereupon becomes locked by a tooth on the serrated bar 56 owing to the off-centre pull of spring 59, and the arm 53 is lifted from the leadscrew 25 and pulled back to the starting position under the influence of a spring 60. To effect reproduction of the recording, play switch 71 is closed. This energizes play relay 70 via a contact on record relay 69, and begin switch 64, and remains energized through a pair of contacts on play relay 70, end switch 61, and two pairs of contacts on record relay 69. The record 20 thus commences to rotate and when the contacts 66, 67 close, the play solenoid 50 is energized, and remains energized following the closing of its own contacts, so that the bar 52 moves the transducer 13 on to the record 10 at the point where the track of the recording started. The transducer 13 traverses the record until the arm 53 presses against the stop member 49, which, being locked to the bar 56, forces the said bar endwise on the spring mountings 57, Fig. 3, so that end switch 61 is open circuited. This de-energizes play relay 70 and play solenoid 50 and the arm 53 is lifted from the record and pulled back by the spring 60 to the starting position. If the play switch 71 remains closed another reproducing cycle then commences, and so on, until switch 71 is opened. Specification 679,086 is referred to.