US2466514A - Magnetic recording and reproducing device with means to prevent accidental erase of record medium - Google Patents

Description

Aprll 5, 1949. VAGTBQRG 2,466,514

MAGNETIC RECORDING AND REPRODUCING DEvICE WITH MEANS TO PREVENT ACCIDENTAL ERASE OF RECORD MEDIUM Filed Nov. 23, 1944 M 5 Sheets-Sheet l MAGNETIC RECORDING AND REPRODUCING DEVICE WITH MEANS TO PREVENT ACCIDENTAL ERASE April 5, 1949. H. A. VAGTBORG 2,466,514

OF RECORD MEDIUM Filed Nov. 25, 1944 v s Sheets-Sheet 2 Aprnl 5, 1949. H. A. VAGTBORG 2,466,514

MAGNETIC RECORDING AND REPRODUCING DEVICE WITH MEANS TO PREVENT ACCIDENTAL ERASE I OF RECORD MEDIUM Filed Nov. 23, 1944 3 Sheets-Sheet 3 I V l Patented Apr. 5, 1949 MAGNETIC RECORDING ANDREPRODUCIN G DEVICE WITH MEANS TO PREVENT ACCI- DENTAL ERASE'OF RECORD .MEDIUM Harold A. Vagtborg, Chicago, 111., assign'or to Armour Research Foundation of Illinois Institute of Technology, a corporation of Illinois I ApplicationNov-ember 23, 1944, Serial-No. 564,824;

3 Claims.

This invention relates toamagnetic recording and reproducing device and more. articularly to a magnetic recorder of "either the magazine loading type or the spool loading type, in which safety means: is provided to prevent erasing: or injury to professionally recorded records or other records. of a permanent nature.

One of the principal features and objects of the present iIIVBI'ItlOIIIiS tO provide anovel magnetic recording and reproducing 'device of the magazine loading type in which means is pro:- vided to distinguish between magazines having a record thereinof apermanent nature andmagazineshaving arecordathereinor a blank wireupon which recordings may bemade and then removed.

Another object of the-present invention is to provide a novel magazine for holding a magnetizable medium.

.A further object of thein-ventionis to provide novel in.terlocking.:means. between the recording circuit of a magnetic recorder .andpthe magazine.

Another and still furtherobiectof the present invention is 'to. provide novel means "for selectivelydistinguishing between wire carrying spools wherein with spools of one typeinterlocki-ng means is provided which will preventtheerasing head of the magnetic recorderirom. being energized and. which will preventany new recording being made on the wire o'f the. magnetic 're.cord in-g device.

Still another and further objectv of th'e'present invention is to: provide 'a novelumagne'tizable medium carrying device and mounting therefor.

The novel features which IIbelie-ve to bexcharacteristic of my invention are set forth with particularity-in the appended claims. My invention itself; however, both as to its manner z'ofv construction and method of operation, together with further-objects and advantages thereof, may best be understood by reference to the following description; taken in connection with the a'ccom panying drawings, in which:

Figure 1 is a schematic wiring diagram of 'a magnetic recording and reproducing device;

Figure 2 is an isometric view of a wire magazine which may be usedwith a magnetic recording and reproducing device of the type schematically shown in Figure v1.;

Figure 3 is an end viewof a wire magazine in place on the deck or panel of a magnetic recording and reproducing device with-thedeck. or panel shown in section;

Figure 4-is an-end view similar toFigure 3 but showing a magazine similar to the "magazineof '2 Figures 2 and 3 but in which a variation of the safety device is provided; I

Figures 5 and. 6.. illustrate a modified 'form of the present invention wherein wire spoolsor-reels are employed outside of a magazine, and wherein with certain spools (Figure 6) areprovided safety means to prevent undesired demagnetization;

Figure 7 is a switch of the type employed in the mechanism shown in Figures 5. and 6 with its-cover removed;

Figures 8 and 9. are variations of the second embodiment of the invention shown in Figures 5 and 6 but wherein the spools having a, permanent recording thereon arev provided with an annular groove on the rear face instead of. an annular rib; and I Figures 10 and 11 are views illustrating a third embodiment of the. present invention showing wire spools. or reels-mounted on the panel of a magnetic recording device.

Referring now to the first embodiment of the present invention. illustrated in Figures 1 to 4 of the drawings, I have shown, in Figure 1, 'a schematic wiring diagram of a magnetic recording and reproducing device. More particularly, the magnetic recording and reproducing device includes a magnetic recorder head l0 which is in the general shape of a U having-inturned confronting polar portions II and. I2. This core member of the magnetic 'head is provided with a magnetizing winding l3 which operates both as-a magnetizing coil and as a pick-up coil,. depending upon whether the device. is being used to make a recording on or receivev a transcription from the magnetizable medium 14. This magnetizable medium I4 is preferably in the form of a steel wire such for example as a medium carbon or a stainless steel wire of approximately .004 inches in diameter.

The electrical circuit with which the magnetizing head H3 is connected includes a stage I 5 of preamplification which is used to give additional amplification of a microphone pickup when a microphone is being used, and is also used for additional amplification when the device is being used as a reproducer. It also includes a conventional audio-amplifier I 6 which may be of any suitable design. This audio-amplifier I6 is connected to, the pie-amplification stage l5 and also to a jack 11 through which the circuit may be connected to a radio receiver. Suitable biasing potentials and power for the pre-amplificati'on stage and amplifienas well. as for other portions of the circuit presently to be described, are obtained from a power pack or power rectifier gen erally designated by the reference character I8. This power rectifier may be of any of the conventional transformer rectifier tube types, and is arranged to receive energy from an alternating current source through a plug IS. A switch 20- is also preferably provided in this circuit to provide convenient switching for the power pack.

When the magnetic head I is being used as a recording device, a relatively high-frequency alternating current is preferably supplied to the coil |'3 in addition to the audio wave supplied from the amplifier Hi. This provides an alternating current bias for the head which gives particularly good results. This high-frequency current is obtained from an oscillator 2| which is connected to the input circuti of the magnetic head In through a coupling condenser 22. The oscillator is also used to supply energy to the erasing head 23 which is in the form of a coil surrounding, or in close proximity to the wire Hi.

The output of the audio-amplifier I6 is connected through a coupling condenser 24 to a filter equalizer circuit 25 and then into the input circuit of the magnetic head through the conductor 26. The audio amplifier I6 is also connected to a loud speaker 21. As will now be explained, the magnetic head is arranged to be con nected to the input of the pre-amplifier stage l and thence through the amplifier IE to the loud speaker 21 when it is desired to reproduce what is already recorded on the wire l4. When the magnetic head I0 is being used to make a magnetic recording on the wire [4 it is connected to the oscillator 2| through the coupling condenser 22 and also to the output of the amplifier I6 through the equalizer network or filter 25. In order to accomplish this, suitable switches are provided, as is illustrated in Figure 1. More particularly, the input of the pre-amplifier stage I5 is connected through a switch 28, a conductor 29 and a switch 38 to one side of the coil l3 of the magnetic head Ill. The switches 28 and 30 are of the single pole double throw type. The conductor 29 is preferably shielded as at 3|, the shield being grounded as at 32. When the switch 30 is moved from its full line position to its dotted line position, as shown in Figure 1, the conductor 29 is grounded. When the switch 28 is moved from its full line position to its dotted line position, the pre-amplifier is connected to a conductor 33 which extends through a switch unit 34 to a microphone terminal switch 35. A switch 38 is provided in the conductor 26 in such a manner as to reverse the end of the coil l3 to which the conductor 26 is connected. It will be noted that the right-hand end of the coil I3 is grounded as at 31'. A switch 31 is provided for shorting out the equalizer network or filter when the device is being used as a reproducer. Switches 38 and 39 are also provided in the circuit leading to the radio receiver jack H and in the power supply circuit to the oscillator, respectively.

While it has not been specifically shown, it will be understood that suitable means is provided to move the wire l4 and this preferably is energized from the same power source as the power pack l8.

The above description of a typical magnetic recording and reproducing device is believed sufficient for a full understanding of the novel teachings of the present invention. The physical structure of the above described recording and reproducing device will not be specifically illustrated except to indicate the manner in which the wire is handled. In the preferred embodiments of the present invention the magnetic recording and reproducing device is equipped with a magazine such, for example, as the magazine 40 shown in Figure 2. This magazine 40 contains a pair of spools or reels 4| and 42 upon which the wire I4 is mounted. These spools or reels 4| and 42 are mounted on shafts 43 and 44 respectively. The ends of each of these shafts 43 and 44 are provided with pins 45 and 46 to provide a positive clutch engagement with suitable driving spindles (not shown) which are arranged in the machine to cause rotation of the spools.

The magnetic head i0 is contained within the magazine 40 and it is suflicient for an understanding of this invention to know that when the magazine is dropped into place in the machine and the recording unit is energized, the spools are rotated to cause relative movement of the wire M with respect to the head It). Figure 3 illustrates the magazine 4|! disposed in place in a cradle or pocket 41 mounted in the upper deck or panel 48 of a magnetic recording and reproducing device. Mounted below the pocket 41 are the three switch units 34, 38 and 38 whichhave been described in Figure l.

The magnetic recording and reproducing device diagrammatically represented in Figure 1 is of such character that it may be used to make new magnetic records on the wire I4 or it may be used to reproduce the recording which is already on the wire l4. In actual use there will be occasions when the wire |4 contains a recording which it is undesirable to erase either intentionally or accidentally. Such recordings might be those of a symphony impressed upon the wire by a professional recording company, or might be a record of events which should be preserved. When records of this character are being used in the machine, it would be extremely unfortunate if the switches were accidently thrown to a position where the erasing head 23 is energized or where the coil I3 is connected to the output of the amplifier l6. There are other occasions where a recording may have been made On the wire I from an incoming radio program through the Jack I! or through the microphone connection 35, which is of a temportary nature. In order to re-use the wire the equipment must be of such a character as to enable demagnetization of the wire and rerecording thereon.

One of the principal features of the present invention is to provide magazines for these difierent above uses which are similar in every character with the single exception of a special safety device which is associated with the records of a permanent nature and which will prevent the oscillator 2| from being energized. Such an arrangement is shown in Figures 2 and 3 of the drawings, wherein the magazine 40 is provided with a projecting pin 49 on the under surface thereof. When this magazine is dropped into place in the pocket 41, the pin 48 projects down through the opening 50 and engages the end of an actuating rod 5| to which the bridging contacts 52 of the switches 34, 38 and 39 are connected. This causes the bridging contacts to snap to their uppermost positions and thus causes disengagement of the stationary contacts 53 and 54 of each of the switches 34, 38 and 38. A switch of the type herein illustrated is of the over-center snap-action type. These switches are of such acharacter that downward movement of the stem 5| causes anupward snapping of the bridging members 52, while upward movement1.:of- -.thestem .1 l' causes the xbridgingzmem bers tomsnapato :their lower apositionsiin .engagement with the stationary contacts :53 :and. 54. These switches 34, 38tandr39, =with't-heir bridging-contacts .52 inthe upper'pgosition are in:an:.unstab1e :position, andzupon release of the pressure on the .upper endzof' the .stem '51 the bridging contacts 52' will snap back to their lowerpositions.

'- "From the :above: description 1 it will be apparent that when av magazine having a projecting pinv laisthereon is dropped into place the switches 34, 381 and '39 :are open. This prevents operation of the .device as a recorder and also prevents energization of the erasing head. The same general type ofmagazine, but nothaving -a pin 49 "thereon, dropped into place, will not cause opening of the switches 34, 38 and =39-and' the device may then be used either as a recorder or reproducer, depending upon how the otherswitches in the circuit are thrown.

-A variation of the: foregoing device is illustrated in Figure 4 of the drawings. More particularly, the microswitches 34, 38 and 39 are so arranged that the upper contacts 55"and 56 are the ones which are connected into the electric circuit, and the lower contacts 53 and Marc dummies. It will thus be understoodthat when the stem'member 5| carrying the bridging contacts 52 is in itsupper position, all of the switches. 34, '38 and 39are open, while when the stem member 5| is depressed downwardly the switches 34, 38 and 39 are closed. In this type of'arrangee ment, a magazine 5-7 is provided having a recessed portion 58 therein when it isbeing usedto house wire having a permanent recording thereon. When such a magazine is employed, the insertion of the magazine 5! into the-pocket 41 will not effect actuation of the normally open switches 34, 38 and 39,, and the device cannot, therefore, be used'to record, nor will the erasing. head 23 .be energized. When a magazine is inserted, however, having a perfectly fiat base wall,v the base wall will .engage the end of the stem member 5| and cause closing of the switches 34, 38 and-39.

Asecond embodiment. of the present invention is illustrated in Figures 5, 6' and 7 of the drawings. More. particularly, in this embodiment of the invention the wire i4 .is mounted on at'akeofi spool 59 which is carried on the shaft 60. The shaft 60 extends through a bushing 6| in the front panel 82 of the magnetic recording and reproducing device (not shown). The switches 34, 38 and 38 are mounted as a gang switch, only the front switch 34 of the gang being shown. These switches are of a type similar to those described in connection with Figure 3 of the drawings. Each includes a stationary contact 63 and a stationary contact 64 which are bridged by a bridging contact 65 carried on a pin 66 which is mounted for limited longitudinal movement. A leaf spring 6'! is connected at an intermediate point to the pin 66 and is engaged at one end by a notch 68 in the housing 69 of the switch. It is engaged at its other end by a v-shaped member which is securely mounted on a shaft 1! which is arranged for limited rotational movement. The distance from the shaft H to the notch 68 is slightly less than the length of the spring 61 so that the Spring 67 is arranged to stop between two positions. A stop member 12 is provided which limits the downward movement of the spring 61. This spring 6! differs from the arrangementsshown in Figure .33; in -that it has 'tworstable positions; one position beingwith the "bridging contact in. -.engag.ementwith the stationary contacts 63 and 64 and the other position being with the bridging contact 65::inanopen position and thespring-(i! in engagement with thestop 7.2. This is important "for a; reasonwhich will presently be apparent.

A crankarmor link 13 is rigidly secured to the end of the shaft 1! which proiectsoutof' the switch housing E59. This arm 13 is slotted asat'14 to seize a pin 15 carried 'on' a follower member -16. It will also .be understood that the. shaft 'l'i proiec'tsthrough all of the'switch cas ingsandthus actuates three switches which are the three switches diagrammatically represented, as '34, 38 and 38 in Figure lot the drawings; The sha'ft H also carries an L-shaped finger 'fl which :projects through an opening I8 in the front panel 6201 the instrument. When the shaft LI is in theposition asshown in Figure- 5 of' the drawings, the switches 34, 38' and 39 are closed. When an ordinary spool or reel 53"ismounted on' the shaft 6| the reel 58 does not contact the follower member I6 'and'the switches: 34, 38 and 39 remain in their closed position. If,=on the other hand, -a reel 19 is-provided which is similarin every character to the reel 59 with the exception that it is provided with a rearwardlyprojecting flange 80, the follower member 'l't isengaged and snaps the-spring fi'l'throug'h its over-centerposition. In snapping through its over=eeriter position, the spring-'61 carries the followermember lt rearwardlybeyond the point where the 'flange-Bdengages it. 'Itwill thus be observed that "there is no friction between the reel. 19 and the follower 16 during operating of the .unit.

Them-ashamed finger 1-! .is for the purpose-of resetting the device after the reel 19 has been removed. "It will be observed that this L-shaped finger 'klsha-srmoved outwardly through the opening :18 when :the bridging contact 65' moves to its: open "position. In order-to reset the devicethe outerend' of the L-shaped finger F! is depressed, which willagain' cause the spring 6 1 to'pass :through itsover-centerposition to close thexabridging contact :65 against the contacts .63- and-64.

Axvariation of this embodiment of the invention is shown in Figures 8 and 9 of the drawings. More particularly, the switch units 34, 38 and 39 (of which only unit 34 may be seen in the drawings) are the same type of unit as the switch unit shown in Figure 7, with the exception that this unit has been turned upside down. More particularly, the switch is mounted in such a position that when the L-shaped finger H is in the position as shown in Figure 8 of the drawings, the switches 34, 38 and 39 are open, while these same switches are closed when the L- shaped finger I1 is in the position as shown in Figure 9 of the drawings. In this variation of the second embodiment of the invention, a spool or reel 8| is provided with an annular recess 82 in the back face thereof when the wire I4 wound thereon carries a recording of a permanent nature, and against which accidental erasure is to be prevented. This recess 82 lies opposite the end of the follower 16 and when the reel BI is mounted does not in any way disturb the position of the follower 16. It will thus be seen that the switches 34, 38 and 39 will remain in their open position under such circumstances. If, on the other hand, a reel such as the reel 83 shown 7 in Figure 9, is mounted on the shaft 60, it will strike the follower 16, force the spring 61 through its over-center position and cause a closure of the switches 34, 38 and 39.

A third embodiment of the present invention is illustrated in Figures 10 and 11 of the drawings. In this form of the invention the switch units 34, 38 and 39 are of the same type as that described in connection with Figures 8 and 9. Instead of the arm 13 on the shaft H, however, an L-shaped arm 84 is provided. This arm 84 projects down through the opening 18 in the panel 62. When the arm is in its right-hand position as shown in Figure 10 of the drawings, the switches 34, 38 and 39 are in their. closed position, while the converse is true when the arm 84 is in its left-hand position. More particularly, when the arm 84 is in its left-hand position the switches 34, 38 and 39 are open. When a reel 83 is mounted on the shaft 60, the outer peripheral flange of the reel will not strike the finger 84. The switches 34, 38 and 39 will thus remain in their closed position and the device may be used for either recording or reproducing. If, however, a reel 85 having a rear flange 86 of greater diameter than the front flange 81 is mounted on the shaft 60, the rear flange 86 will strike the finger 84 and rotate the shaft 1| to cause the switches 34, 38 and 39 to open. A spool or reel of this character may be used to contain wire having a permanent recording thereon.

While I have shown particular embodiments of my invention, it will, of course, be understood that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims, to cover all such modifications as may fall within the true spirit and scope of my invention.

I claim as my invention:

1. In a magnetic recording and reproducing device, a magnetic sound head, electrically energized means for magnetically recording sound on a wire, electrically energized means for reproducing sound previously magnetically recorded on a wire, said device being arranged to receive and operatively mount wire carrying spools in operative relation with respect to said head, switch means in the electrical energizing circuit of said recording means, said device having means thereon responsive to spools having a predetermined rim shape and dimension to open said switch means when such spools are mounted on said device.

2. A magnetic recording and reproducing device of the type wherein intelligence is recorded by varying the magnetic condition of a lengthy magnetizable medium along its length, said device including electrically energized elements to impart varying degrees of magnetization to said medium as it passes thereover to record intelligence thereon, a shaft to receive a spool supporting said medium before it travels over said elements during operation of said device, and a switch operable to deenergize said elements, said switch having an operating element extending in direction parallel to the axis of said shaft to bear against an annular portion of the edge of said spool to control the energization of said elements in accord with the axial extent of said annular portion.

3. A a magnetic recording and reproducing device of the type wherein intelligence is recorded by varying the magnetic condition of a lengthy vmagnetizable medium along its length, said device including electrically energized elements to impart varying degrees of magnetization to said medium as it passes thereover to record intelligence thereon, a shaft to receive a spool supporting said medium before it travels over said elements during operation of said device, and a switch operable to deenergize said elements, said switch having an operating lever extending in direction parallel to the axis of said shaft and mounted for rotation relative to said axis to bear against the outer periphery of the end flange of said spool to control the energization of said elements in accord with the diameter of said flange.

HAROLD A. VAG'I'BORG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,560,721 OReilly Nov. 10, 1925, 2,213,768 Merriman Sept. 3, 1940 2,321,812 Heller June 15, 1943 2,364,556 Somers Dec. 5, 1944

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