US2476848A - Variable resistance phonograph pickup and system - Google Patents

Description

y 1949. w. ECKHARDT ET AL 2,476,848

VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEM Filed July 5, 1945 2 Sheets-Sheet 1 INVENTORS WALTER LECKHARDT MADISON CAWEIN ATTORNEY July 19, 1949. w. ECKHARDT ET AL 2,476,848

VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEM Filed July 5, 1945 2 Sheets-Sheet 2 INVENTOR WALTER L. ECKHARDT MADISON CAWEIN ATTORNEY Patented July 19, 1949 VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEM Walter L. Eckhardt and Madison Gawain, Fort Wayne, Ind., assignors, by mesne assignments, to Farnsworth Research Corporation, a corporation of Indiana Application July 5, 1945, SerialNo: 603,362

16. Claims. 1

This invention relates generally to phonograph pickup devices and more particularly to a phono. graph pickup device adapted to translate sound.

characteristics which make themresonant in a.

portion of the audio frequency band. Toprovide such devices having. a relatively uniform frequency responseover the entire audible frequency range entails numerous design problems.

The relatively high mass of suchdevices causes them tdhave a sluggish respons inthe higher frequencies of the. audible range andprevents instantaneous responseof the-stylus to the higher.

frequency vibrations whichare-cut in arecord. This results in a relativechange of phasebetween the low frequency sound signals and the high frequency sound signals so that the high frequencieshave a time delay with respect to the low frequencies. Thus the sound which is reproduced does not have the same. phase relationship between the high and" low frequency components ascompared to the-phase relationships which were established on the record.

The characteristics of conventional pickup'devices such' as those enumerated in the foregoing discussion make it particularly difiicult to provide a pickup device whichis capable of responding to sound recordings of both the hill and dale type and the lateral cut. type. Ordinarily a pickup device which responds to both types of. recordings must necessarily have a relatively higher mass than a pickup which is designed to respond to a single type of recording. Thus the quality of response of "a conventional pickup capable. of responding to both types of recordings is even lower than that of a pickup which is specifically designed to respond to a single type of recording.

Accordingly, it is the principal object of this invention to provide a phonograph pickup device having a uniform response characteristic over substantially the entire audible frequency band and adapted to translate hill and dale recordings or lateral cut recordings.

A further object of this invention is to provide a phonograph pickup device,the mass of which is reducedwith respect to that'of conventional pickup devices.

A still furtherobject or this invention is; to

2 provide a phonograph pickup deviceof suchmass as to. preserve the phase.relationshipbetween.re-

corded high and: low frequency. components-of a sound signal.

Anotherobject offthis. invention is to provide circuit means for cooperating with a pickup capable oi-v translating recordings of the hill-and daletype; orwof. the lateral cut. type whereby to control the electrical outputof thedeyice and sea lectivelyi effectv aresponseto one or the other types of recordings.

' Still another objector this inventionis to provideca circuit. adapted. to convert the pickup device from one'which responds to hill and dale recordings to. one-which responds to lateral cut recordings. or. vice-versa and at the same. time prevent. amplification of recordings of. the nonselectedtype.

In accordance with this invention there is provided a phonograph pickup device consisting of a flexible means, means for flexing the flexible meansandia plurality of'resistance members disposed on theiflexiblemeam' so as to be variable by vertical andhorizontal' flexing or the flexible means.

In accordance with a" further feature of this invention; there is provided aphonograph pickup device adapted" to reproduce. records. of the hill and dale'type' or of the-lateral cut type. This device comprises a flexible means having a portion atone end adapted to be fixed to a phonograph pickup'arm together with an extended portion having a stylus fixed at its free end for fiexingthe' extended portion in response to bill and dale sound tracks orlat'eral out sound tracks. There provided-on the'extended portion of the flexible' -means an electrically resistive means for effecting" control of an electric circuit when the extended-portion is'flexed in a' vertical or horizontal plane;

For electrically controlling the output of the phonographipickup' device provided. in accordance'with this invention, there is provided an electrical circuit consisting of. potential dividers connected'across' certain components of the electrically resistive meansinthe pickup device for rendering'certain ones of said components effective for responding to hill and dale sound tracksandcertain others of said components ef fective to respond'to' soundtracks of the lateral cuttype;

For a better understanding of. the invention, together'with other and further objects thereof; reference is made tov the following description, taken in 'connection" with the accompanying drawings, and its scope will be pointed out in the appended claims:

In the accompanying drawings:

Fig. 1 of the drawings is an elevation of the pickup device provided in accordance with this invention together with its associated pickup arm which is shown partially in cross section;

Fig. 2 is a plan bottom view of the device illustrated in Fig. 1;

Fig. 3 is an exploded perspective ofthe pickup device provided in accordance with this invention;

Fig. 4 is a cross section taken online 4-4 of Fig. 3;

Fig. 5 is a fragmentary cross section of the pickup device taken on line '5-5 of Fig. 4;

Fig. 6 is a circuit diagram illustrating a control circuit provided in accordance with this invention and incorporating the electrically resistive means which form a portion of the pickup devices illustrated in Figs. 1-5;

Fig, 7 is a perspective view of a modified form of the pickup device illustrated in Fig. 3 with the stylus mounting omitted; and

Fig. 8 is a cross section taken on line 8-8 of Fig-7.

Referring now to Figs. 1, 2 and 3 of the drawings, there is illustrated a preferred modification of this invention consisting of a pickup arm I, a pair of clamping members 3 and 4 fixed to pickup arm I by suitable screws 6 and 1 together with sound translating pickup l0. Pickup device In includes an enlarged portion l l which is adapted to be clamped between elements 3 and 4 by means of screws l2 and |3. Integrally formed with the enlarged portion ll of pickup element I is an extended portion l to which is attached, in a manner to be described hereinafter, a stylus 16 for tracking the groove of a hill and dale type record or a lateral cut record.

Pickup element l0 may be formed of any type of insulating material such, for example, as plastics like Celluloid, polystyrene or other materials of similar flexibility and mass. On the extended portion I 5 of pickup element H] a number of grooves 18, preferably four, are out which may be of the order of 1 5 inch in depth whereby to provide vertical and horizontal surfaces on which may be painted or otherwise deposited layers of electrically resistive material 20, 2|, 22 and 23 such, for example, as finely divided carbon particles similar to graphite. Thus, there is provided comparatively long strips of electrically resistive material. The strips cover the parts of the surface of portion l5 located in the quadrants between the vertical and horizontal axes of portion Hi. When portion is flexed, the contact pressure betweenthe carbon particles changes thereby to change the electrical resistances of the strips.

The layers of resistive materials 20, 2|, 22 and 23 are adapted to respond electrically to sound records of either the hill and dale type or of the lateral cut type. When the extended portion I5 is flexed in a vertical direction as in the case of hill and dale records, the carbon particles along the horizontal surfaces 25 of the strips 20, 2|, 22 and 23 are, in effect, moved to vary the contact pressure between adjacent particles. For example, when portion I5 is flexed downwardly, the particles on the upper horizontal surfaces tend to separate whereas the particles on the lower horizontal surfaces tend to move closer to one another. On the other hand, when portion I 5 is flexed upwardly the reverse is true.

Thus, the resistance changes in the upper and lower surfaces 25 are equal and opposite and the currents which flow through the resistive strips may be utilized to operate a push-pull amplifier device as will be described hereinafter.

When the extended portion [5 is vibrated in a horizontal plane as in the case of lateral cut records, the vertical surfaces 26 of the resistive strips are stressed in a manner similar to that described in connection with the horizontal surfaces 25. V In a similar manner, there is produced equal and opposite changes of resistance which may also be utilized to operate a push-pull amplifier device.

In order to provide electrical contact with the resistive strips, they are continued from extended portion l5 onto the surfaces of enlarged portion H. Thus, for example, resistive strip 2!] is terminatedon enlarged portion 5 i by a conductive coating 28 and resistive strips 2|, 22 and are also terminated on enlarged portion H in conductive coatings 29, so and 3|, respectively. Clamping member 3 includes fixed terminals 33 for engaging conductive coatings 29 and 3|. Clamping member includes as an adjustable clamping portion thereof a terminal strip 35 which is adjustably mounted on member 2 by setscrews 35. Member 35 includes terminals 38 affixed thereto for engaging with conductive coatings 29 and 3|. When pickup device It) is initially affixed to clamping members 3 and it is placed so that the enlarged portion Ii protrudes between the clamping members with the conductive coatings 28, 29, 30 and 3! in juxtaposition with terminals 33 and 38. Setscrews 36 may then be rotated to move terminal strip 35 and contact members 38 into engagement with the conductive coatings to provide intimate electrical contact therewith. Terminals 33 and 38 may be connected to the exterior of clamping members 3 and 4 by conductors 40.

For supporting the stylus at the free end of extended portion l5, there is provided member 42 having a conductive coating 43 which may be clamped to extended portion 5 by means of screws Ml, thereby to provide a support for stylus i6 and intimate electrical contact between all of the resistive strips 2!], 2|, 22 and 23. For providing an electrical connection to coating ie, there is a bore 4! (Figs. 4 and 5) within extended portionl5 through which extends conductor 48. At the free end of enlarged portion N, there is provided a conductive pin 5| to which conductor ie may be connected and to which may be connected conductive coatings 52 which are disposed on the outer surface of enlarged portion ll. Coatings 52 may be connected to the exterior of clamping members 3 and 3 by means of contacts 53 on the clamping members and conductors 54.

Referring to Fig. 6 of the drawings, there is illustrated a circuit adapted to control and amplify the electrical variations produced in conductive strips 20, 2|, 22 and 23. These strips appear in Fig. 6 as resistors indicated by identical reference characters. The member 42 (Fig. 3) for joining the ends of the conductive strips, is indicated by the same reference character in Fig. 6. For providing a means for converting the pickup device from a hill and dale pickup to a lateral cut pickup, or vice versa, there are provided potentiometers 69, El, 62 and 63 which are connected across resistors 2l-20, 20-22, 22-23 and 23-2 I, respectively.

The slider 65 of potentiometer 6B and slider 66 of qootentiometerifi I? are. connected to a point 68 icommon'sto resistor 12 :and lpotentiometers :60 andndl Thei point 1'68 ;is also connectedthrough;

conductm: 57' to the cont1ol"grid"of vacuum. tube 10. Point. 68 is also connected -through resistor HiriThe plate resistcrs ia and T! are also conthe positive side of the source of potential nected t'o the pos'itiv'e side-of source-l4 and to the.

platesof tube's lfl iand 'll'. The slid'ers Hi and. 8B 'tjfpotentiometefs 52 and 63;irespectively', are

connected to the -point fi'i c'ommon to resistor 23 cuitfof -converting the pickup device 89 for operatingin con-junction with hill and dale type record grooves or lateral cut record grooves. If it is desiredto utilize the pickupdevice in conjunetioli withhill and dale recordgrooves, po-

'25 vither a volume control or a switching cirtentioine'ter slider 65' is moved; to theextreme left position toshort-circuitresistor Gil-while po- .7 tentiometer slider 19 is simultaneously movedto its iiextre'met 1 rightnposition toL- short-circuit re sistor fi Thustcurront flows from: source 14 through resi'ston iii-through resistors ZU-a-nd 2! I to aground-i and-f also from source :14 through .ree

sister-s13, r22 andi23 toground As the resistance of zthez 'resistors changes in response to the sound wavesccut :in .thetrecord; avariable potentials. are

tentiom'ete'rs '6 l ands-5 iv-may;- be :varied to effect a volume-controls;

ln thezcase of laterali cutirecords, potentiometer sliders; ::and: ma'yx-be moved to their. extreme lower andaupper :positions: respectively to} shortcircuituespectively resistors 5i and 63.- Thus the changesgofresistance efie'cted by la'teralzvibration.-;-.

of "the vpickup.; devicecause --variable potentials to onthe grids-citric tubes Wand H 2 For volume control, :potentio-meters fiil and 62 maybe varied.

Referring to Figs. 7 and 8 of the drawings;.,.

there, is-illustr-ated-aa modification/of the pick? up -.-:levice l G. Illethifi modification, the extended:

portiom- 15;15 provided with rectangular chan-z nelstfifi efil,;92-and--93: wliich .aredisposed-on the verticaland. horizontal axes of portion I l 5, as best illustrated-in Fig. 8. The channels are-filled-with a resistance material asin .the preferred modification tovfornrresistive strips 2G, .2l,.22. and 23..

These-strips are continued to enlargedportion H to form terminalistrips .28, 29., 30, 3!. and 52,.

as.-,in.-th e. preferred modification... The stylusesupportingtdevice=42Qmay be secured to the free.

end of portion 15 in. the. same manner asrillu'se.

trated in Fig. 3. j

In'ithisfmodification, flexure of portion 15 by a hilland dale record groove varies theresistance of,,strips-29and 221 byequal and oppositeamounts similarly to provide a push-pull electrical signal. .A conventional push-pull amplifier may be utilized to amplify. the signals and switches may be provid'edifoi' connecting-whichever, strips are de-. sirdtobe effective."

Frd'mothetioregoing; it is .1 evident; .that atherewls y; provided in accordance with this invention; a

phonograph .-pickup::':device:: 'havingzua substan:

tially Zuniform' frequency response; characteristic and adapted tc translate :either hilliand dale recordin'gs'or lateralgcut recordings. The; mass of.- this pickup: device is such: that :its: inertia: effects J do not prevent H instantaneous; response of the 1- stylus; whereby -allaudiblen frequencies are :re-

produced faithfully? with 11 respect to itheir phase.

While the I drawings: illustrate. the preferred features of this invention; "it will be obvious. to those skilled inth'e artthatthe inventive con-. cept includes various modifications; For example; the' pickup member c l 0 is illustrated ashavin 7 channels for-receivi'n'g resistance material but it is within the'scope of this invention to -coat the outer surface 'of-the 'pickup member with strips of resistance material of a desired thickness whereby-to provide a pickup device which will operate in 'the same manner as that illustrated in the drawings.- Itis also. obviousthat various other arrangements of contact strips maybe'provided on pickupdeVice-JO such ,--for example; as

foil or rigid metallic' stripss Further, itis not necessary to utilize the particular type ofclamping members-shown in the drawingses any suitable mechanicafarrangement falls'within the" scope of thisinventionw While there has been-described what, at present;-is considered the preferred embodiment of the invention; it will-beobvious to those skilled in the art that various changesand modifications may be made therein without departing from the invention, and therefore, it is aimed in'the appended -claims' ;to'-" coverall" such" changes and modifications as -f all within the true spirit" and scope of the invention."

What is claimed is:

lpsound' "translationapparatus' comprising flexible means, meansj'iixed thereto for flexing said flexible means; a plurality ;of1channels disposed'on said flexiblemeans, certain of said channels comprising surfaces disposedat angles to the surfaces" of certain others of'said channels and resistive material fixed'tosaidisurfaces.

2. Sound z'translation apparatus. comprising flexible means'y'means' fixed at one end thereof forflexing said; flexible means, a plurality of channe'ls'diagonally disposedon the outer surface of said flexible meansanol'strips of resistive material fixed to "said surfaces.

3. Sound translation apparatus comprising flexible 'means, means fixedthereto .forflexing.

said'flexiblemeans, a plurality of channels dis: posed on: saidv flexible means, each channel comprising surfaces disposed at 90 angles to one. another andstrips'of carbonaceous material fixed to "said surfaces;

4. Sound translation apparatus comprising flexible means, means. fixed at one end thereof for flexing' said flexiblejmeans, a plurality of channels disposed on the outersurface ofsaid flexible means, each channel comprising surfaces disposed-at'90 angles to oneanoth'e'r and strips of'carbonaceous material fixed to'said surfaces.

5. Sound "translation apparatus comprising flexible means 'havinga portion'at one; end adapted to be fixed to a phonograph pickuparm and-an'extended portion having four' channels spaced fIOllTOI'lG another on diagonal'lineswith respectfto the longitudinal axis of said means, a stylus fixed -at*the' free'end of said extended portion'for' flexing it in a vertical or horizontal1i plane and electrically resistive material fixed to the surfaces of said extended portion which define said channels.

6. Sound translation apparatus comprising flexible means having a portion at one end} adapted to be fixed to a phonograph pickup arm and a reduced portion having four channels spaced from one another and disposed in the four quadrants defined by the vertical and horizontal axes of said portion, a stylus fixed at the free end of said extended portion for flexing it in a vertical or horizontal plane and electrically resistive material fixed to the surfaces of said extended portion which define said channels.

7. Sound translation apparatus comprising flexible means having a base portion at one end adapted to be fixed to a phonograph pickup arm and an extended portion having four channels spaced from one another and disposed in the four quadrants defined by the vertical and horizontal axes of said portion, a stylus fixed at the free end of said extended portion for flexing it in a vertical or horizontal plane and carbonaceous particles fixed to the surfaces of said extended portion which define said channels.

8. Sound translation apparatus comprising flexible means having an enlarged portion at one end adapted to-be fixed to a phonograph pickup arm and an extended portion having four channels spaced from one another and disposed in the four quadrants defined by the vertical and horizontal axes of said portion, electrically resistive means fixed to the surfaces of said extended portion which define said channels, conductive means secured to the free end of said extended portion in contact with said resistive means, terminal strips on the surface of said enlarged portion some of which are connected to said resistive means, a conductor extending from said conductive means through said extended portion into said enlarged portion and electrically connecting said conductive means to one of said terminal strips and a stylus fixed to said conductive means for flexing said extended portion in a vertical or horizontal plane.

9. Sound translation apparatus comprising flexible means having an enlarged portion at one end adapted to be fixed to a phonograph pickup arm and an extended portion having four channels spaced from one another and disposed in the four quadrants defined by the vertical and horizontal axes of said portion, carbonaceous strips fixed to the surfaces of said extended portion which define said channels, conductive means secured to the free end of said extended portion in contact with all of said carbonaceous strips, terminal strips on the surface of said enlarged portion some of which are connected to said carbonaceous strips, a conductor extending from said conductive means through said extended portion into said enlarged portion and electrically connecting said conductive means to one of said terminal strips and a stylus fixed to said conductive means for flexing said extended portion in a vertical or horizontal plane.

10. Sound translation apparatus comprising flexible means having a portion at one end adapted to be fixed to a phonograph pickup arm and an extended portion, said extended portion including vertically and horizontally disposed channels a stylus fixed at the free end of said extended portion for flexing it in a vertical or horizontal plane and electrically resistive elements fixed to the surfaces of said channels in alignment with the vertical and horizontal axes of said extended portion.

11; Sound translating apparatus comprising flexible means, means fixed thereto for flexing said flexible means, first resistance means disposed on said flexible means so as to be variable by vertical flexing of said flexible means, second resistance means disposed on said flexible means so as to be varied by horizontal flexing of said flexible means, amplifier means including an input circuit and voltage dividing means for coupling either said first resistance means or said second resistance means to said amplifier means.

12. A sound-translating circuit comprising electrical pickup means consisting of a plurality of resistors adapted to be varied in response to hill and dale or lateral cut recordings, means for shunting successive pair of resistors for controlling the response thereof, push-pull amplifier means including a pair of input circuits and conductor means for coupling said shunting means to said input circuits.

13. A sound-translating circuit comprising electrical pickup means consisting of a plurality of resistors adapted to be varied in response to hill and dale or lateral cut recordings, potentiometers connected across said resistors for controlling the response of said resistors, push-pull amplifier means including a pair of input circuits, conductor means for coupling the sliders of one pair of potentiometers to one of said input circuits, conductor means for coupling the sliders of another pair of potentiometers to the other of said input circuits and a source of potential connected between said amplifier and said potentiometers.

14. A sound-translating circuit comprising electrical pickup means consisting of a plurality of resistors adapted to be flexed in response to hill and dale or lateral cut recordings, means for connecting said resistors to a common point, potentiometers connected across the free ends of said resistors to form a star connection whereby successive pairs of resistors are shunted by said potentiometers for controlling the response of said resistors, amplifier means including a pair of vacuum tube input circuits, means for coupling the sliders of one pair of adjacent potentiometers to one of said input circuits, means for coupling the sliders of another pair of adjacent potentiometers to the other of said input circuits and a source of potential connected between said common point and points of said star connection between the potentiometers of each said pair.

15. A sound-translating circuit comprising electrical pickup means consisting of a plurality of resistors adapted to be flexed in response to hill and dale or lateral cut recordings, means for connecting one end of each resistor in common, potentiometers connected across the other ends of said resistors to form a star connection whereby successive pairs of resistors are shunted by said potentiometers for controlling the reponse of said resistors, push-pull amplifier means including a pair of input circuits, means for coupling the sliders of one pair of adjacent potentiometers to one of said input circuits, means for coupling the sliders of another pair of adjacent potentiometers to the other of said input circuits and a source of potential connected between said common connecting means and points of said star electrical pickup means consisting of a plurality,

of resistors adapted to be flexed by vibration in first and second planes in response to the hill and dale or lateral cut recordings, means for connecting one end of each resistor to ground, potentiometers connected across the other ends of said resistors to form a star connection whereby successive pairs of resistors are shunted by said potentiometers for controlling the response of said resistors, push-pull amplifier means including a pair of input circuits, conductor means for coupling the sliders of one pair of adjacent potentiometers to one of said input circuits, conductor means for coupling the sliders of another pair of adjacent potentiometers to the other of said input circuits and a source of potential connected 10 between ground and points of said star connection between th potentiometers of each said pair.

WALTER L. ECKHARDT. MADISON CAWEIN.

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

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