US2426061A

US2426061A - Electric phonograph pickup of the capacity type

Info

Publication number: US2426061A
Application number: US564539A
Authority: US
Inventors: Snepvangers Rene
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1944-11-21
Filing date: 1944-11-21
Publication date: 1947-08-19
Anticipated expiration: 1964-08-19

Description

7' R. SNEPVANGEIQS 2,426,061

ELECTRIC PHONOGRAPH PICKUP OF THE CAPACITY TYPE Filed Nov. 21, 1944' INVENTOR. RENE'VSNEPVANGERS ATTORNEY Patented Au 1a, 1947 STAES OFFICE ELECTRIQ PHONOGRAPH PICKUP (BE THE CAPACITY TYPE Application November 21, 1944, Serial No. 564,539

15 Claims.

This invention relates to signal translating apparatus, and more particularly to a phonograph pick-up device of the capacity type.

Phonograph record reproducing systems of the frequency modulation type employing capacity pick-ups have been introduced in recent years and have been found to have many desirable features. Due to (l) the tone arm or pick-up arm resonances of conventional pick-up supporting arms and (2) the pinch effect in records of the lateral cut type, distortion of the reproduced sound results, It is desirable, of course, to eliminate such distortion insofar as possible, and the primary object of my present invention is to provide an improved form of capacity type pick-up device which will reproduce sound with a minimum of distortion of this type.

More particularly, it is an object of my present invention to provide an improved capacity type pick-up which will have a low mechanical impedance and a high signal to noise ratio, which will afford better tracking of the record groove by the needle, and which will result in much less record wear.

Another object of my present invention is to provide an improved capacity type pick-up device which has a wide range of response.

Still another object of my present invention is to provide an improved capacity type pick-up device for phonograph records of the lateral cut type which will have good vertical compliance to compensate for the pinch effect, good lateral or horizontal flexibility to compensate for the tone arm inertia and resonance, and high torsional stifiness to avoid introduction of extraneous sounds.

A further object of my present invention is to provide an improved capacity type pick-up device as aforesaid the movable electrode or plate of which may be of the reed type and which may be formed in one piece, if desired.

It is also an object of my present invention to provide an improved capacity type pick-up device which is simple in construction, inexpensive in cost, easy to manufacture and assemble, and highly eflicient in use.

In accordance with my present invention, I provide a pick-up having a stationary electrode and a vibratory electrode for cooperation with the stationary electrode. The vibratory electrode may be of the reed type and has a first portion which is flexible in one plane or direction for movement toward and away from the stationary electrode to cooperate therewith as a capacitor, and a second portion which extends from said first named portion and is flexible for movement in a second plane or direction normal to the first mentioned one. Either one of these portions may be suitably anchored to an appropriate anchoring element whereby to maintain the first named portion in cooperative relation with the stationary electrode, and the other of said vibratory electrode portions may be provided with a record engaging needle or tip which cooperates with the groove of the record. At the same time, the vibratory electrode is stiff enough to greatly resist torsional forces. A vibratory electrode so constructed readily compensates for pick-up arm resonances and for the pinch efiect, and provides reproduction which is markedly free from distortion.

The novel features that I consider characteristic of my present invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of several embodiments thereof when read in connection with the accompanying drawing in which Figure 1 is a top, plan view of one form of pick-up device according to my present invention with certain parts broken away for the sake of clearness and with the cover removed,

Figure 2 is a sectional view on the line IIII of Figure 1 and with the cover in place,

Figure 3 is a sectional view taken on the line III-III of Figure 1,

Figure 4 is an enlarged view of the vibratory electrode and the mounting therefor,

Figure 5 is a view similar to Figure 4 showing a different form of my present invention,

Figure 6 is a perspective view of the vibratory electrode of Figure 5,

Figure 7 is a sectional view taken on the line VII--VII of Figure 6,

Figure 8 is a side view, partly in section, showing still another form of my present invention,

Figure 9 is a bottom, plan view of the vibratory electrode structure of Figure 8 and the anchoring element therefor,

Figures 10, 12 and 13 are side views similar to Figure 5 of still other forms of my present invention,

Figure 11 is an end view of the vibratory electrode structure of Figure 10 as seen from the right, and

Figure 14 is a view partly in plan and partly in section taken on the line XIV-XIV of Figure 12.

Referring more particularly to the drawing wherein similar reference characters designate corresponding parts throughout, there is shown, in Figures 1, 2 and 3, a pick-up arm I carrying a supporting plate 3 of insulating material. The support 3 has connected thereto on its underside, by means of a screw or the like, a conductive, L-shaped member 1' having a downwardly extending, vertical portion la which constitutes the stationary electrode. Also mounted on the support 3 is an anchoring block 9 to which is secured a vibratory, conductive, reed-like member II. The member H may be made of a sheet or strip of resilient material and is formed with a first portion I la one end of which is secured to the block 9 and which cooperates with the stationary plate la, being spaced therefrom by an air space or other suitable dielectric to constitute therewith a capacitor. The portion Ila of the vibratory electrode has a laterally, forwardly and downwardly extending portion lib which terminates in a loop or socket lie in which is received a record engaging tip or needle I3 of sapphire or the like. A suitable cover I4 is mounted on the supporting plate 3 around the structure thus far described to protect the electrodes from injury.

The vibratory electrode portion Ha is flexible in a horizontal direction for movement toward and away from the stationary electrode la in response to signal forces imparted to the needle tip I3 by the sound groove of a record R. The vibratory portion llb, on the other hand, is flexible in a vertical direction to compensate for the pinch effect of the groove. If desired, a damping block 15 of Viscoloid, printer's roll, or the like may be secured to the supporting block 3 and arranged to engage the vibratory portion llb for the purpose of damping undesired oscillation or vibration thereof. Electrical connection to electrodes of the pick-up device may be made by means of a pair of leads I! within the. pick-up arm I.

In the form of the invention shown, in Figures 5 to 7, the vibratory electrode 2| may be made of rectangular wire one reed like portion 2la of which is formed into a wedge shape cross section, as shown in Figure 7, by compressing the wire laterally or horizontally, and a second, reedlike portion 21b of which is formed by compressing the wire vertically. The portion 2Ib may be anchored to the anchoring block 9 and provides vertical flexibility. The portion Zia cooperates with the stationary electrode 1a and provides lateral flexibility. The needle socket or 10op2lc is formed on an extension of the part 21a and carries the needle tip [3.

In Figures 8 and 9, there is shown a vibratory electrode comprising a reed-like plate 3Ia which cooperates with the stationary electrode la and from which there extends downwardly in a plane at right angles to the plane of the reed portion 3la a second portion 3lb terminating in the needle tip socket 310. The portion 3Ia is flexible horizontally and the portion 3th is flexible vertically. A cover 33 may be placed around the electrode plates and is provided with an opening 35 through which the vibratory part 31b extends. The cover 33 may be of conductive material and may be grounded, as shown. An advantage of this cover is that it may serve as a guard for the pick-up device in the event that the pick-up is accidentally dropped onto a record and the portion 3lb flexe excessively.

The forms of the invention shown in Figures 10, 12 and 13 are somewhat similar to those of Figures 4 and 8. In Figure. 10, the vibratory electrode structure comprises a reed-like plate 4 la from which is bent up a forwardly and downwardly extending, vertically flexible curved portion 4 lb which terminates in a needle tip retaining socket 410, The reed portion 41b is bent up from the bottom or lower end of the reed-like plate Ma. In Figure 12, a similar construction having a vertical, reed-like plate 5m anchored to the block 9 is shown, a forwardly and downwardly curved reed-like part 51b being bent from the forward end of the part am. As in the previous modifications, the part 5lb i flexible in a vertical direction and is disposed generally in a plane at right angles to the plane of the reed part 5| a, the latter being flexible in a horizontal direction. If desired, a gusset or the like 53 may be formed at the bend where the parts 5m and 5| b are joined for the purpose of stiflening. The modification of Figure 13 is quite similar to that of Figure 12 except that the vertically flexible part 6 lb of the vibratory electrode is bent up from a corner of the horizontally flexible part 6 la and extends angularly across the corner of the latter part. As in the modification of Figure 8, the reed portions ilb, Bio and Bib of Figures 10, 12 and 13 are disposed generally in planes normal to their respectively associated reed portions Ha, 5| a and Bid.

From the foregoing description, it will be apparent to those skilled in the art that I have provided an improved capacity type pick-up device having the advantages set forth above. Although I have disclosed several embodiments of my present invention, it will, no doubt, be apparent to those skilled in the art that many other embodiments thereof, as well as variations in the particular ones described, are possible. I therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A phonograph pick-up device of the capacity type comprising a stationary conductive member and a vibratively supported conductive member, said vibrative member having (1) a first portion spaced from said stationary member and constituting a capacitor therewith, said first portion being flexible in a direction for movement toward and away from said stationary member in re sponse to signal forces applied thereto whereby to vary the capacitance of said capacitor, and (2) a second portion contiguous to and extending from said first portion, said second portion being flexible for movement in a second direction normal to said first named directio and being stiff in said first named direction.

2. A phonograph pick-up device according to claim 1 wherein said first and second portions are disposed essentially in two planes normal to each other, said first portion lying in a plane substantially parallel to that of said stationary member, and said second portion lying generall in a plane normal to said first named plane.

3. A phonograph pick-up device according to claim 1 characterized by the addition of an anchoring element, one of said portions being anchorecl to said element, and characterized further by the addition of a needle element carried by the other of said portions for cooperation with a record groove.

4. A phonograph pick-up device according to claim 1. characterized by the addition of an anchoring element, said second portion being anchored to said element, and characterized further by the addition of a needle element carried by said first portion for cooperation with a record groove.

5. A phonograph pick-up device according to claim 1 characterized by the addition of an anchoring element, said first portion being anchored to said element, and characterized further by the addition of a needle element carried by said second portion for cooperation with a record groove.

6. A pick-up device accordin to claim 1 characterized in that said first portion is wedge-shaped in cross section,

'7. A pick-up device according to claim 1 characterized in that said first portion is constituted by a reed-like plate.

8. A pick-up device according to claim 1 characterized in that said first portion is constituted by a reed-like plate, and characterized further in that said second portion comprises a reed-like member extending from said plate.

9. A pick-up device according to claim 1 characterized in that said first portion is constituted by a reed-like plate, and characterized further in that said second portion comprises a reed-like member extending from said plate in a plane normal to that of said plate.

10. A pick-up device according to claim 1 characterized in that said stationary member and said first portion of said vibratory member are disposed in vertical, substantially parallel planes, characterized further in that said first portion is constituted by a reed-like plate, and characterized still further in that said second portion of said vibratory member comprises a reed like member which extends away from said plate and is disposed normally thereto.

11. A pick-up device according to claim 1 characterized in that said stationary member and said first portion of said vibratory member are disposed in vertical, substantially parallel planes, characterized further in that said first portion is constituted by a reed-like plate, and characterized still further in that said second portion of said vibratory member comprises a reed like member which extends downwardly away from said plate along a curve and is disposed normally thereto.

12. A phonograph pick-up device of the capacity type comprising a stationary conductive member, a vibrative conductive member, said vibrative member having (1) a first portion spaced from said stationary member and constituting a capacitor therewith, said first portion being flexible in a direction for movement toward and away from said stationary member in response to signal forces applied thereto whereby to vary the capacitance of said capacitor, and (2) a second portion connected to said first portion, said second portion being flexible for movement in a direction normal to said first named direction and being stiff in said first named direction, an anchoring element, said second portion being anchored to said element and said first portio extending from said second portion, and a needle element carried by said first portion for cooperation with a record groove.

13. A phonograph pick-up device of the capacity type comprising a stationary conductive member and a vibratively supported conductive member, said vibrative member having (1) a first portion spaced from said stationary member and constituting a capacitor therewith, said first portion being wedge-shaped in cross section and being flexible in a direction for movement toward and away from said stationary member in response to signal forces applied thereto whereby to vary the capacitance of said capacitor, and (2) a second portion connected to said first portion, said second portion being flexible for movement in a second direction normal to said first named direction and being stiif in said first named direction.

14. A phonograph pick-up device of the capacity type comprising a stationary conductive member and a vibratively supported conductive member, said vibrative member having (1) a first portion spaced from said stationary member and constituting a capacitor therewith, said first portion having a transverse cross section which varies in width and being flexible in a direction for movement toward and away from said stationary member in response to signal forces applied thereto whereby to vary the capacitance of said capacitor, and (2) a second portion connected to said first portion, said second portion being flexible for movement in a second direction normal to said first named direction and being stiif in said first named direction.

15. A phonograph pick-up device according to claim 1 characterized in that said first and second portions of said vibrative member are integral with each other.

RENE SNEPVANGERS.

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

UNITED STATES PATENTS Number Name Date 2,322,621 Farrow June 22, 1943 2,320,416 Dally June 1, 1943 FOREIGN PATENTS Number Country Date 116,481 Australia Jan. 20, 1943 524,619 Great Britain Aug. 12, 1940 310,762 Great Britain Apr. 30, 1927