US1967335A - Electrical pick-up - Google Patents

Description

July 24, 1934. N. STEIGMAN ELECTRICAL PICK-UP Filed Sept. 18, 1929 INVENTOR I Israel N .fizelg'man Patented July 24, 1934 UNITED NT "OFFICE i 11,967,335)" I t V i g IsraelN. S teiginan, Brooklyn, NY. f Application September 18; 1929, Serial Nb. 393,383

;j9 Claims (claim-1:00.41)

' This invention relates to electrical pickup; apparatus designed to" convert stimuli, sucheas sounds, movements, or mechanical vibrations into such pulsating 'electriccurrent as may be later broadcast, reproduced or recorded, and

' which correspond withoutmaterial'distortion to the original sounds,-movements Qrvibrations. Such apparatus usually comprisesa dynamo. or generator including'amagnet for generating a magneticfield, an'armature movable in the'field under the impulse of a stimulus, and coils in whichcurrent is generated on the movement oi the armature. r s

As a particular applicationiof my. invention, my improved apparatusmay-be used tomchange the mechanical vibrationsof a stylus operating in the groove of a phonograph record, into: equivalent electricalimpulses, or my apparatus may be used as a microphone? as desired. The electrical output of the apparatus may later, be amplified, as for instance, by means of well known thermionic amplifiers, and made to operate loud speakers or recording instruments, such as photnographs, telegraphones or thelike, orait may i f be used directly to modulatehigh frequencyv circuits for broadcasting purposes,-

ing means, such as, for example, springs ninterposed rubber members, cloth, or the like Such damping means not only causes material loss of the efiective power of the sti ulusoperating ,the'apparatus, which power, it is understood, is extremely minute in the first instance, but the damping meanshas the additional defect of so restraining the free vibration :of the armature as to cause undesirable and often, gross distortion of the reproduction, resulting in lack of correspondence, of==the output with the stimulus.

Distortion of reproduction-in previously known apparatus otthis type alsojoccurs gowing to. the

r fact that vibrationsat a certain frequency,;corresponding to the natural frequency of vibration of the damping means, can be; imparted to thearmature more easily than otherifrequencies, which other frequencies are therefore; transmitted with greater difficulty and are moreor lessirepressed, preventing faithfulreproduction, and resulting in further diminution of the effective power of the stimulus, Furthermore, pickup apparatus heretofore in use has been not only mechanically restrained by the damping means referredtto above, but the armatures thereof have been of same means h'ave therefore been employed .justmerit of the predetermined area of tiguous armature and poler faces.

excessive Weight, due to the loading thereof with coils and other devices. The additional weight is enough to'resilst the free vibration of the armature under the impulse "of the stimulus and is further, enough 'to cause undesirable wear of the parts and of the stimulus where for example, phonograph records are used as the transmitting medium. "Finally, such weighted armatures are subject to the defect that considerable energy in transmission is lost and consequent distortion occurs due to the inertia of' the comparatively heavyfarmature, and the consequent diificulty of starting and stopping the movement ther customarily to correct the dlstortion caused by the aoove mentioned. defects. Said means has usually taken the form of electrical or. Wave filf'ters for eliminating .or altering the undesirable portionsof the electrical reproduced impulses or waves, but such filters result in further undesirable absorption of energyQand are an experisive andlinefficient means for approximating Ithej desired result.

invention contemplates the provision of a device, consisting merely. of the control and adthe con- My invention, further contemplates the provision of means for so mountingrand vibrating'the armature of the pickup that the faces of said armature vibratein a plane substantially at right angles to the magnetic lines of force, and so that said armature is entirely free of mechanicalre- .straint against vibration other than that 'due Ito its own weighhjaiidfrdm which springs and damping means are entirely, eliminated, the arr'nature nevertheless being maintained in its prop- Her; position intl emagn etic field. My invention Ifurther' contemplates the provision of .an arma- Qture oi minimum weight whereby .the inertia thereof against free vibration is reduced to a minimum; with consequent maximum efficiency in faithful reproduction and-with maximum utiliza- ,tionof the energyof thestimulus put thereon, so ,thatan extremely high..-degree of perfection of 'reproductionmay be attainedwithout the necessity for,the,use ofwave filters. ,My invention {further contemplates,the'iproduction or" a simple and comparatively inexpensive and efficient apmay also be operated as a microphone, if desired.

The various objects of my invention will be clear from the description which follows, and from the drawing, in which,

Fig. 1 is a perspective view of the preferred form of my improved pickup, showing the device in use for the electrical conversion of sound in connection with a phonograph record.

Fig. 2 is a similar view of one of the magnet poles and of a portion of the armature therefor, showing a modified form of the pole and armature faces, the areas of which govern the degree of reluctance in the magnetic circuit, and therethrough govern the extent and characteristics of the pulsations of the electrical output.

Fig. 3 is a diagrammatic view of my improved apparatus, showing the magnetic circuit therefor and showing, further, the connection thereof to a suitable amplifier means such as a thermionic" transformer.

Fig. 4 is a perspective view of a modified form of my apparatus illustrating a modified arrangement of the magnet poles and armature.

Fig. 5 is a similar view of the same, showing another modified arrangement.

Fig. 6 is a similar view of the same, showing a modified form of armature and showing the connection thereof to a suitable sound responsive means whereby the apparatus may be used as a microphone, and

Fig. 7 is a similar view of another modified form of my apparatus, showing a different form of the faces of the pole pieces and armature.

Figure 8 shows a modified form of my device in which the armature pivot is mounted above the airgap.

In that practical embodiment of my invention which I have illustrated by way of example, in Fig. 1 a suitable magnet 10, which is preferably a permanent magnet, is provided with a pairof poles 11 and 12 which may be disposed in various positions, as is shown in the remaining figures, and as will be more fully explained hereinafter. The magnet 10 may be secured or held in proper stationary position by means of a suitable extension 13 thereon, as may be found convenient or desirable.

Wound about the poles 11 and 12 and preferably spaced somewhat from the preferably plane terminal faces 14 and 15 respectively thereof are the coils 16 and 17 respectively, each composed of nal or other form presenting two or more operative facets to the magnetic field induced by the magnet 10. As illustrated, two facets 21' and 22 are provided on the pole face as 14 and two similar facets 25 and 26 are provided on the armature face 19, though it will be understood that any desired number of facets disposed on planes angularly arranged may be used instead, as will be obvious to those skilled in the art and hence which need not be shown.

I prefer, however, that a single'groove only be made in each of the armature and pole faces, and

that said groove be rectangular 'in cross-section,

though I do not desire to be understood as limiting myself to a single groove of any definite shape,

as above explained. As illustrated in Fig. 1, the width of the armature 18 is very little less than the distance between the faces 14 and 15 of the adjacent poles, whereby the armature is arranged with the faces 19 and 20 thereof as close as is physically possible to the respective pole faces 14 and 15. I prefer to so mount the armature that the gap between the armature faces and the pole faces, while being of minimum extent, is permanent as regards its width, and invariable for all practical purposes.

I further prefer to so mount the armature 18 that the faces 19 and 20 thereof move in a path parallel to and across the pole faces 14 and 15 and at afixed distance therefrom, and are constrained to move in the path described substantially without mechanical restraint against vibration in said path. Toward this end, the armature is pivoted about a suitable axis.

As shown in Fig. 1, I prefer to provide a nonmagnetic shaft as 29 passing through part of the armature and spaced from the poles 11 and 12 and terminating in conical bearings 30 mounted in suitable supports as 31 secured to the magnet 10. A stylus as 32 may be secured to the armature 18 on the opposite side of the pivot shaft 29 from that on which said poles are arranged, though it will be understood that the stylus may be on the same side of the shaft as are the poles, if desired. Said stylus may be held to the armature by means of a chuck 33 secured by a suitable adjusting screw as 34. The stylus 32 is intended to be inserted into the undulated track or groove 35 of the phonograph record 36, whereby rotation of the record in the usual manner causes the stylus 32 to oscillate about the pivot shaft 29 under the impulse of the variations in said track and thereby causes the armature faces to vibrate correspondingly, across and parallel to the pole faces.

No coils are provided on the armature so that the groove 35 has only a minimum amount of weight to move and the armature is free from restraint against vibration except that occasioned by the inertia due to its own weight. This inertia, it will be seen, is also reduced to a minimum by reason of the simplicity of the armature and the possibility of reducing its weight to a minimum. Stops as 37 of non-magetic material may be provided for limiting the vibratory movement of said armature, said stops preferably projecting from the magnet 10 and being so spaced apart as to maintain the armature 18 at all times in the magnetic field of the poles 11 and 12.

Should the armature therefore be subjected to an unusual force tending to throw it completely out of the magnet field, the stops 37 nevertheless maintain the'armature within the range of the magnetic force, which is sufficient to pull the armature back into its proper position without the necessity for using mechanical means such as springs or the like. In other words, the magnetic force in the field is the agent serving to maintain the armature in its operative position without other aid. 7

The coils 16 and 17 are suitably inter-connected as by means of the conductor 38 (Fig.

3), the terminal wires 39 ammo of said conductor being connected to suitable amplifying apparatus 41, as willbe seen from Fig. 3.

The magnetic reluctance of the magnetic circuit may be varied by changing the position of the armature in the magnetic field of the poles,

by movement of the armature'across and substantially parallel to the pole faces and not from agaeasas pole to pole. By so varying the magnetic reluctance, a current varying in intensity and fre-- quency in exact correspondence to the vibration of the armature, is induc'edin the 'coi1s 16.and 17 and may be used for thepurposes heretofore mentioned. a a i w. i

As illustrated in Fig.4, the armature42 isarranged across the ends of the magnet poles 43 and 44, the respective polefaces 45and 46 of which are arrangedin thesame plane. Thepivoting shaft 47 for the armature may be similar to the shaft 29, butonly' oneface as 48 ofthe armature is'operative in this modification.

As shown in Fig. 5, the pole faces 49 and 50 of the'magnet 10 are arranged at substantially right angles to each other so that the surfaces 51 and 52 of the armature 53are correspondingly arranged although the operation thereofg'as above described, is notmater'ially-altered. 4 i i As illustrated in Fig. 6, thearmature 54 may be connected to the cone 55 or other suitable 'diaphragm by meansof the connecting member 56, said cone or diaphragm being vibratory under the impulse of sound waves. a n

The pole faces of the magnet 10 illustrated in Fig. 6 are shown substantially identical with those shown inFig; 4and therefore neednot be further described. The armature '54, however, maybe pivoted on a shaft as 57 arranged parallel to the pole-"faces 45and 46; The vibration of the armature across the pole faces without changing the width of the gap may be made to occur, however, in substantially the same way irrespective of the arrangement-of the pivot therefor.

In Fig. 7, I have shown another form of mountingwhereby the armature 58 may vibrate without change in the width of the gap. In this case,

the axis of the pivot shaft 59 lies in a plane perpendicular 'to the plane of themagnet 10, in distinction from the arrangements of the pivot shafts 29, 47 and 57, the axes of which lie in planes parallel tothe plane of the magnet; This arrangement of the pivot shaft 59 necessitates tangular as in the other modifications.

Meansmay be provided for predetermining the characteristic of the currentinduced in the coils 16 and 17 on predetermined motion of any ofthe armatures 18, 42, 53, 54 and 58 across their'pole faces.

Said means may take the form of a multiplicity of facets as 21, 22, 25 and 26form'ed bymaking one or more grooves as 23 and 24 in the pole faces and armature faces" respectively. illustrated in Fig."2', I prefer that said means take the form of a variationin the shape of the periphery and extent of-the areas of the pole facets 64 and 65 and of the armature facets 66 and 67. The variation in said areas may be effected by changing the shape of the sides of the grooves 68 and 69 made in the magnet pole faces and in the armature faces, respectively, and consequently, in a change of the shapes of the sides 70 and '71 of the pole facets and of the sides 72 and '73 of the armature facets.

In other words, a variable change of area of the eifective armature and pole surfaces may result on movement of the armature through a predetermined angle in different positions of the of facetsare provided onthe pole faces.

armature. Ifz there- -were ino 'grooves in .the armature and' pole facesgand the width. of the pole, faces were-greater than-the maximum amplitude of vibration of. the armature; no current would be. induced in the :.coils. vIf the sides of the grooves were vertical," then there would. be a uniform variation in the current induced in the coils 3 during a single movementof the arma' ture in one direction, butif the sides of the groove were straight "but inclined at'ani angle other than aright angle to the. upper an'd lower faces. of the poles, then the variationisuniformly variable. Again, if the sides of the groove: were curved along predetermined lines, then the variation would be variably variable and1may:be predetermined to produce an output of the desired characteristic, as. should be.c1ear' to those skilled in the art. For examplejtheburves .of thegroove sides 'may be. so designedsthat if. the armature were to'swing through an angleoftwo degrees and during that swing, to generate one volt, a

.swing of four degrees in the same direction might be caused to induce one and one half or five or and other number Of'VOltS, and not two volts,

and a swing of sixdegrees might be caused to faces and armature faces and that said areas may.

bevaried as desired. As: shown in Fig. .7, the grooves 74 and75are"made triangular-instead of rectangular, the grooves in all cases being preferably deep 1 enough to' prevent any. undesired passage of flux; As shown in Fig. 8,- a multiplicity of grooves and aconsequent multiplicity The pivot for the armature 81 is further arranged above the' pole's instead of belowthe poles as in Fig". 1 to give a somewhat greater leverage.

It will also be se'enthatby providing an armature free of-coils and'vibrating said armature so that the armature faces travel in a plane substantially parallel to the faces of the poles orin a cylindrical surface concentric with: thepolefaces,

I have produced a simple andefiicient mechanism operating 'with a minimum waste of energy and accurately responsive to the stimulus applied theretofiwhereby efiicient "reproducion with a minimum of distortion becomes possible.

It willfurther be understood that while 1 preterm so pivot the armature that it moves as above described, the'armaturemay also be. pivoted so asto move atright angles'tothe described direction or acrbssthepoles from topto bottom, if desired, by merely changing the relative position of the pivot on 'thearmature. T It will furtherb'e V understood that while lg have shown a-record having a groove of one type, any type of grooved record may be used as a stimulus to the apparatus and that by means of a suitable diaphragm responsive to vibrations, my improved apparatus may be used as a microphone, if desired.

While I have shown and described a preferred embodiment of my invention, it will be understood, further, that I do not wish to limit myself thereto but intend to claim my invention as broadly as may be permitted by the state of the prior art and the terms of the appended claims.

I claim:

1. In an electrical pick-up, a magnet having poles thereon, relatively stationary coilson the poles, a movablesoft iron armature free of coils and having multi-faceted faces thereon cooperating with the pole faces for varying .the reluctance in the magnetic circuit of the magnet in a variably variable predetermined manner, and. means for pivotally supporting the armature so that the faces of the armature remain at a predetermined distance from the pole faces during the vibration of the armature in response to a stimulus, said means and the stimulus being the only mechanical forces other than said magnet acting upon the armature tocause movement of the armature free from damping and lag effects.

2. In an electrical pickup device, .the combination with pole faces of a magnet of vibratory soft iron armature free of coils and having faces terminating in at least one edge curved in'the direction of its length cooperating with the pole faces and adapted to vary the reluctance in the magnetic circuit of the magnet in a predetermined manner independent of the variation induced by the stimulus, and meansfor pivotally supporting the armature so that the faces of the armature move in a surface parallel to the pole faces. g r

3. In an electrical pickup device, the combination with a pivoted armature, of magnet poles serving as the sole means acting upon the armature to swing it about its pivot into position to maintain it in the magnetic field of the poles, and means for pivotally supporting the armature for vibration across the lines of force of the field and spaced from the poles to transmit to the armature substantially the full force exerted by a stimulus thereon, and a stylus carried directly by the armature. V,

4. In an electrical pickup device, the combina tion with a pivoted armature, of magnetpoles serving as the sole means acting upon the armature to swing it about its pivot into position to maintain it in the magnetic field of the poles, means for supporting the armature for vibration across the lines of force of the field and out of contact with the poles, in response to a stimulus, and means for preventing the vibratory movement of the armature beyond predetermined limits.

5. In an electrical pickup device, the combination with means for inducing a magnetic field, means responsive to variations in the magnetic reluctance of the circuit for producing current, and means for varying the reluctance of the circuit mounted for movement across the lines of force of said field and normally maintained in said field solely bysaid first-mentioned means to utilize substantially the full force of a stimulus applied thereto, said reluctance varying means including a pivoted armature provided with a series of spaced faces lying in the same warped surface, each of saidfaces having at least one longitudinal edge thereof in the shape. of a curve of predetermined 4 shape. 6. In an electrical pickup device, a magnet, grooved magnet poles thereon, coils on said poles adaptedto have currentinduced therein on the variation ofthe magnetic reluctance in the field of said magnet, an armature having grooved faces therein arranged at a predetermined fixed distance from the faces of said poles, said armature being pivoted to maintain said distance constant,,the effective area of the grooved pole faces and the armature faces being-predetermined by shaping the peripheral edges of said faces to control the characteristic of the current induced in said coils.

- 7. In an electrical pick-up device adapted to be actuated by a revoluble phonograph record, a magnet having a pair of poles thereon, each of said poles having a reentrant recess to interrupt the faces of said poles, the longitudinal edges of said recess being of predetermined curvilinear shape so that the pole surfaces beyond the recess are of. variable widths throughout their lengths, a coil wound about each ,pole in spaced relation to the recess therein, a pivoted armature, a stylus adapted to engage the record carried by the armature, means for pivotally supporting the armature so that each face of the armature is maintained at constant distance from the adjacent pole face, the armature faces having recesses corresponding to and similar to the recesses of the pole faces.

8. In an electrical pick-up device, a magnet, a pair of pole pieces extending from the sides of the magnet toward each other and spaced apart,

an armature arranged in the space between said pole pieces, the inner end of each of said pole pieces having a re-entrant groove therein, and the faces of the armature adjacent the pole faces having a similar groove therein and substantially the same shape and size as that of the corresponding groove in the adjacent pole face, means for pivotally supporting the armature for movement across the pole faces while maintaining the distance between the pole faces and the armature facesconstant, a vibratory member adapted to have a stimulus applied directly thereto carried by the armature, and a coil wound about each of thepole pieces and connected to each other and arranged in spaced relation to the grooves of said pole pieces.

9. In an electrical pick-up device, a U-shaped magnet, pole pieces extending toward each other from the sides of the magnet and spaced from the sides of the magnet, and a stylus carried by .the armature below the pivot, said pivot maintaining constant the spaces between the armature faces and the faces of the pole pieces.

ISRAEL N. .STEIGMAN.

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