US1777036A - Magnetic pick-up for phonographs - Google Patents

Description

Patented Sept. 30, 1930 Y PATENT OFFICE cmmco Y; CORONEL, or MANILA, rHrLIrPINE ISLANDS MAGNETIC PICK-UI FOR PHONOGRAPHS Application led March 6,

This invention relates to magnetic pick ups for phonographs, the purpose of which is to translate the vibratory movements of a stylus, when acted upon by a phonograph record,

into 'electrical impulses and to utilize such impulses to actuate suitable acoustic means for the purpose of reproducing in sound the un,

4d ulations or lateral deviations in the sound groove of t-he record. The advantages of devices of this character, over well known sound L box reproduction embodying a diaphragm acting through a tone arm to a horn, are numerous-A and are generally' well known. Chieiiy among these advantages, however, is the fact that more satisfactory reproduction is obtained with almost any desired amplification and the mechanical noises incident to the operation of .a diaphragm are wholly eliminated. Y Furthermore, reproduction through malgnetic pick up apparatus is much more sensitive to movements of aa stylus than the diaphragm, and, accordingly, the sound grooves may be made much smaller and closer together, so that the playing time of the record is materially increased when magnetic pick up reproduction is employed.

Magnetic pick u s have heretofore been suggested and are nown generally to the art, but these prior devices embody numerous disadvantages, certain of which it is the ob- Y ject of the present invention to minimize and other of which it is the objectof this invention to overcome.

The primary purpose of the invent n, therefore, is to provide a sturdy, durable evice which will cooperate with either hill and dale or lateralcut records. Attempts have been made to provide such devices in the `fpast, but my experience with such' devices has shown that while they may operate with a fair degree of etliciency on either one or the other of these types of records, they will not operate with efficiency on yboth types. Such 'devices invariably embody a single stylus adapted toserve in both instances, but when it is attempted to thus operate the device, it is found that it will operate with much greater efficiency on one type of record than on the'other type. So far as I am aware,

1929. Serial No. 344,624.

no' device of the char vcter under considera- Y cut type, both of these mountings beingtconnected with an armature so that such armature. is responsive tothe operation of either 3* of the styli. With the armature is associated a suitable coil positioned between the poles of a permanent horseshoe magnet, the coil being stationary and the armature'loosely placed therein and on independent rubber bushed bearings.

Suitable means is provided for maintaining the armature in neutral position and this means is suiiiciently rigid to -hold the armature in such neutral position notwithstanding the pressure of either stylus upon the record, but nevertheless suiiiciently resilient to allow of vibration of the armature by either stylus. The coil is included in a circuit which is adapted to be connected to the detector tube S0 0f a radio receiving set or to any other suitable electrical apparatus, whereby the pulsating current resulting in the coil from the vibrations of the armature may be .amplified and acoustically reproduced with any desired volume.`

` An important feature of the present invention resides in the simplicity of the structure, the relatively .light weight of the moving parts 'which renders the device extremely1 90 sensitive and the compact association of suc devices into a relatively small housing; y

Another important feature of the invenJ tion resides in the fact that al1 parts of the device are readily accessible and may be easily i removed and replaced in the .event of damage or breakage incident to rough-usuage.

' Features of the invention, other than those specified, will be apparent from the hereinafter description and claims, when read in,100

Vpractical embodiment of the invention,-but

the construction therein shown is to be understood as illustrative, only, and not as defining the limits of the invention.

Figure 1 is a plan view of the device with' the cover plate removed,

Figure 2 is a section on the line 2--2 of Figure 1.

. Figure 3 is Van end view of the device.

Figures 4 and 5 show one way of supporting the device for cooperation with either lateral cut or hill and dale records.

Referring tothe drawings, l designates a permanent, horseshoe magnet provided with pole pieces 2. The magnet and pole pieces are mounted upon a suitable base plate 3 of non-magnetic material, such, for example, as cast aluminum by means of the bolts 4 having nuts 5. 6 designates a bearing plate of nonmagnetic material, preferably brass, shown best in Figure 2 as bent intermediate its ends at substantially 90 degrees, so that one arm of the plate overlies the pole pieces 2, while the other extends between the legs of the magnet. This bearing plate is perforated and the bolts 4 are threaded therethrough to firmly clamp the bearing plate 6 in position..

The arm of 'the plate which extends between.

the legs of the magnet is slotted as shown at 7 and through this slot extends a lever, the fulcrum of which is the pivot 8, which eX- tends across the slot. The lever is of the first class and has arms 9 and 10 of unequal length, the arm 9 being the longer of the two and constituting the armature of the magnet.

Positioned between the pole pieces of the magnet is a coil 26 which is mounted rigidly in position and through the center of the coil is formed a passage of sufficient size so that the armaturepi) may extend through the coil without touching the same and with sufficient clearance to permit vibration of the armature within the coil without contacttherewith.

The free end of the armature 9 is secured in any suitable manner to the stylus bar 14. This stylus bar which is in the form of a lever is pivoted at 15 to one of the pole pieces in such manner as to be insulated therefrom and the long arm 16 of this stylus bar is secured to the armature while the shorter arm 17 is formed to constitute a holder for a suitable stylus which may be secured in place by a thumb screw 18. The short arm' 10 of the armature lever is connected by means of a suitable link 19, preferably flexible, to a second stylus bar 20. This latter Stylus bar has arms of unequal length with the longer arm 21 connected to the link 19, while the shorter arm constitutes a holder for the stylus 22, shown in the drawings as a standard diamond point needle.

It is of course essential to the proper oparnese eration of the device that the armature 9 tend to remain in a substantially neutral posi tion which willno't be materially affected by pressure ofeither stylus upon a record and in ordemto 4provide for; this, so-.called gap equalizers are employed'. These gap equalizers are in the form'of rubber or other resilient plates 23, shown best in Fig. 2. They are secured against th endsof the pole pieces by screws 24 passe 4through metallic washer plates 25. The screws and washer plates firmly hold the equalizers in such position that theireontiguous ends will bear against the opposite sides of the armature 9 and normally tend to hold the armature in the neutral posi- .This coil is firmly secured in place in any suitable manner, such, for example, as by clamping it between the plate 6 and the base plate 3, and it will be noted from Fig.2 that the coil is provided with a central opening through which the armature extends, this opening being sufficiently large so that the armature will not contact with the walls of the opening irrespectivel of the degree of vibration imparted to the armature by either stylus. The wire leads from the coil 26 are designated 27. They are secured to suitable binding posts 28 supported on a block of insulation material 29. This block 0f insulation material is secured in place by a bolt 30 which has two nuts 31 and 32. The nut 31 serves to clamp the block of insulation tightly to the base, while the nut 32 serves to secure one end of a cover 33 in position and also `functions to-tight-ly and rigidly attach the device to a suitable bracket 34. The part 34 is soldered to 35. In place of 34-35, a removable bracket for attaching to the tone arm of the phonograph can be madea part of the unit. The part 35 in practice constitutes any suitable supporting element.

The cover 33 to which I have referred is of suitable non-magnetic material and is Vadapted to enclose all parts superimposed upon the base plate, being held in position b v the nut 32 and also by the nuts 5 of the bolts 4. A suitable opening is provided in the cover plate through which the stylus bar 14 is adapted to operate.

Wires 36 lead from `the binding posts 28 to any suitable amplifying apparatus through any standard combined scratch filter and vol* ume control, such as a radio receiving set which serves to amplify the variable current impulses and prepare them for reproduction by a suitable horn or other sound amplifying means. kThe relatively weak variable electrical currents 4resulting -in the coil through the vibration of the armature 9 are thus sult-l ably amplified and transformed into sound.

The device of the present invention Will be sensitive to all notes and Will perform with uniform reproduction with either lateral cut or hill and dale records.y The arrangement is convertible as stated for either type of record by merely turning, the unit and arm 90 degrees on an independent set of pivot holes onthe arm or arm mounting, or by turning the arm 35 on an especially j ointedl rod working loosely in a hole in a suitable weight.

In Figures 4 and 5, this structure is illustrated generally. 100 designates a suitable weight adapted to rest upon the frame of the phonograph instrument and provided in its top with a socket into which extends a rod 101 joined at 102 and carrying at its top a saddle 103 to which the arm 35' is secured.

vWhen the parts are asshown in Fig. 4, the

ldevice is adaptedto operate upon hill and .dale records, but by' iieXing the joint 90 degrees, the parts will appear as shown in Fig.

5 to adapt the device to cooperate with lateral cut records. Figures 4 and 5 `are illustrative of one of several Ways in which the part 35 be mounted to permit ofoperation of the device with the records of either type.

It can be used as a freely floating weight on the Edison phonographwhen an attachment to the Edison arm is incorporated, thusu'tilizing to the full benet the Edison synchronized feed with all the attendant advantages, and becoming interchangeable with any standard Edison reproducer.

I wishv it understood, however, that the present device is not limited to use on Edison phonographs, but it can be employed on any make of machine to play all ltypes of records.

The stylus bar for the lateral cut records is suitably supported to insulatethe bar and minimize scratch and record Wear, While the gap equalizing members 23, preferably of soft rubber, can he renewedand adjusted Without dismantling the unit thereby preserving the strength ofthe magnet and assuring efficient operation at all times. As a matter of fact, all the parts are simple in 'mechanical construction, rugged and easy Vto adjust and repair. The simple, light, one-V piece armature has relatively little inherentl inertia and permits the faith-ful reproductidn of all notes in the musical scale. The method shown is. only1 illustrative of one method.

VThe foregoing detailed description sets forth the invention in its preferred, practical form, but the invention is 'to be understood as fully commensurate with the appended claims.

, Having thus fully described the invention,

what I claim as new and desire to secure by Letters Patent is v 1. In a magnetic pick-up for phonographs, a permanent horseshoe magnet, a coil positioned between the poles of said magnet, a i

pivoted armature extending through the-coil, and two distinct and separate stylus ba'rs mounted independently of the armat-ure and and dale and lateral cut records, both of Which stylus bars are separately and independently secured to the armature to render adapted to respectively cooperate with hill said armature responsive to the vibrations of either stylus bar.

2. In a magnetic pick-up for phonographs, a permanent horseshoe magnet, a coil positioned between the poles of 'said magnet, and

7 stationary'with respect thereto, a pivoted armature extending through the coil and movable4 with `respect thereto, and two distinct and' separate stylus bars adapted to respectively cooperate with hill and dale and lateral cut records, said stylus bars being respectively secured to the opposite ends of the armature to render saidarmature relponsive to v the vibrations of either stylus 3. In a magnetic pick-np for phonographs, a permanent horseshoe magnet, a coil positioned betweenthe poles of said magnet, a pivoted armature extending through the coil,

'and'two distinct and separate stylus bars adapted to respectively cooperate with hill and dale. and lateral cut records, bothof which stylus bars are secured to the armature brations of either" stylus bar, and .resilient gap equa'lizingm'eans to yieldabl counterbalance the normal pressure on eit er stylus in 'order to maintain the armature in neutral position and permit of vibratory movement of the armature transmitted thereto from either stylus bar.

4. In a magnetic pick-up for phonographs,

a permanent horseshoe magnet a e011 positioned between the poles of said magnet, a pivoted armature extending through the coil,

and two distinct and separate stylus bars pivf oted for vibratory movement in planes perpendicularto one another, said stylus bars ei'ng adapted for cooperation respectively with hill and dale and lateral cut records,

, .l 100 to render said armature responslve tol the v1 A end of the stylus bar connected to the free end of the armature, and a separate and independent stylus bar positioned to vibrate in a plane perpendicular to the irst mentioned stylus bar and operatively connected to the free end of the short arm of the lever, Whereby the armature is rendered responsive to the vibrations of either stylus bar.

6. `In a magnetic pick-up for phonographs, lo a permanent horseshoe magnet provided with suitable pole pieces, a coil positioned between the pole pieces and ixedly .mounted with respect thereto, a first classlever having arms of unequal length supported on a iXedfulerum with the longer arm extending through n the coil in movable relation thereto and constituting thearmature, resilient gap equalizing means for normally maintaining the ar# mature in neutral position, a stylus bar mounted on a fixedV pivot with one end of the stylus bar connected to the free end of the armature, and a separate and independent stylus bar positioned to' vibrate in a plane, perpendicular to the first mentioned stylus bar and operatively connected to the free'end of the short arm of the lever, whereby the armature is rendered responsive to the vibra tions of either stylus bar, each stylus bar coruprising a lever of the first class with arms of unequal length, the long arm being connected tothe armature lever and the short arm constituting a stylus holder.

In testimony whereof I have signed the foregoing speciication.

CIRIACo Y. ooRoNEn

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