US2280763A - Phonographic apparatus - Google Patents

Description

April 1942- w H. J. HASBROUCK, JR 2,280,763

PHONOGRAPHIC APPARATUS Filed March 30, 1940 Patented Apr. 21, 1942 PHONOGRAPHIC APPARATUS Harold J. Hasbrouck, Jn, Merchantville, N. J., assignor to Radio Corporation of America, a

corporation of Delaware Application March so, 1940, Serial No. 326,896

6 Claims.

This invention relates to phonographic apparatus, and more particularly to a signal transand the noises radiated either directly by the pick-up device and/or the records themselves in reacting on the needle. Various attempts have been made to reduce these extraneous noises,

such as using lighter needles or designing the pick-up for lower effective mass, but these and other similar attempts have not solved the problem satisfactorily.

The primary object of my present invention is to provide an improved pick-up device which will be free from the aforementioned defects.

More particularly, it is an object of my present invention to provide an improved pick-up or sound translating device which will not cause the record with which it is cooperating during reproduction to radiate extraneous sounds and which will not in itself produce such sounds.

Another object of my present invention is to provide an improved sound translating device as aforesaid which will operate with a very light needle pressure upon the record, thereby assuring longer record life.

Still another object of my present invention is to provide an improved signal translating device wherein the operating parts are light in weight and have minimum inertia effects during operation.

A further object of my present invention is to provide a signal translating device for phonographs which is particularly adapted for use with records of the lateral cut type.

Still a further object of my present invention is to provide an improved piezo-electric generator for the reproduction of sound from phonograph records wherein the operative parts of the generator are well protected against injury.

Another object of my invention is to provide an improved phonograph needle for use in sound reproducing devices of the electro-mechanical type.

It is also an object of my present invention to provide an improved sound translating device of the type set forth which is very simple in construction and highly emcient in use.

In accordance with my invention, I preferably employ a piezo-electric unit of the multiple-plate flexing type, the plates or crystals being disposed in a horizontal position. To one end of the unit is attached a rigid torsion member which is adapted to oscillate slightly and thereby set up torsional strains in the piezo-electric unit which converts them into corresponding electromotive forces. The free end of the torsion arm may be provided with the conventional needle socket in which my improved needle may be removably secured. The needle comprises a rigid arm which extends downwardly to within about of an inch of the record and in the lowerend of which is swaged or otherwise suitably secured a wire of tungsten or other suitable wear resistant material having a diameter of approximately 0.006 inch to 0.010 inch. The wire is substantially L- shaped and extends from the aforementioned arm about inch, being flexible both vertically and horizontally, or, in other words, in planes both normal to and parallel with the record. The free end of the tungsten wire is bent downwardly for about 7 of an inch to provide the record groove engaging tip. Practically all motion is confined to this piece of wire, the arm itself, the torsion yoke, and the piezo-electric unit moving very little. A suitable guard protects the wire from injury and a rubber bumper located adjacent the bend in the wire helps take shocks such as that resulting from accidental dropping of the pick-up on the record. An additional guard is provided behind the record engaging tip of the needle to prevent the tip from being accidentally bent backward. My improved pick-up preferably operates with a vertical pressure of about one-half ounce to one ounce and is good for at least 2000 playings on shellac records by reason of the wear resistant quality of the tungsten wire. Since the wire needle is arranged to have a maximum of vertical flexibility, it is obvious that it will impart only very small forces to the record and thus reduce the generation of the wave motion in the record and subsequent radiation of the noise ordinarily created by such radiation. Furthermore, since the diameter of the wire needle remains constant throughout its life, it is obvious that the needle groove will not be subjected to undue wear.

The novel features that I consider characteristic of my 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 one embodiment thereof when read in connection with the accompanying drawing in which Figureil is a top plan view of a sound translating device constructed accordingto my present invention and mounted on a suitable nick-up arm,

Figure 2 is an enlarged plan view of the pickup device itself,

Figure 3 is a sectional view taken on the line III-III of Fig. 2,

Figure 4 is a fragmentary sectional view showing the position of the needle in relation to associated parts when the needle tip is in engagement with a record, and

Figure 5 is a fragmentary detail view looking in the direction of the arrow A of Fig. 3.

Referring more particularly to the drawing, wherein similar reference numerals indicate corresponding parts throughout, I have shown a casing member lformed in two parts and preferably hermetically sealed to enclose a piezo-electric unit comprising a pair of piezo-electric crystals 3 of Rochelle salt or the like, with which are associated terminal foils 5 of conductive material in well known manner, the crystal unit 3 being spaced from the casing l by suitable blocks I of damping material such as that known commercially as DuPont Viscaloid No. '7. The casing I also carries a torsion yoke 9 within a rubber sleeve II, the outer or free end of the torsion yoke 9 being provided with a needle socket l3, and the inner end of the member 9 being provided with a yoke or clamp I5 which firmly clamps one end of the crystal .unit 3. The device thus far described is more or less conventional and may be mounted upon a suitable pickup arm I! which is pivotally mounted on a suitable support (not shown) for movement over a phonograph record in well known manner.

Removably received within the socket i3 and clamped to the torsion member 9, as by a set screw I9, is a rigid arm or rod 2| which extends downwardly substantially at right angles to the plane of the crystal unit 3. Suitably secured to the lower end of the rod 2|, as by swaging or the like, is a forwardly extending thin, flexible, L- shaped needle 23of music wire or the like and preferably formed of tungsten or some other wear resistant material or alloy of metals. The

major portion of the needle 23 extends substan- When the pick-up device is in cooperative-relation to a record, the crystal unit 3 occupies a substantially horizontal position. Th needle 23 is flexible in all directions (that is, through 360) in a plane at right angles to the major portion, or the horizontal arm, of the needle but it is fairly rigid in torsion. Consequently, the needle tip 25 can faithfully follow the contours of a lateral cut groove and impart a twisting action or torsion to the torsion member 9 through the connecting arm 2 I, the needle itself movin arcuately as a whole about the axis of the yoke 9 as a center without itself undergoing any substantial twisting action since it is rigid in torsion. This, in turn, sets up torsional strains in the piezoelectric unit 3 to generate electromotive forces corresponding to the mechanical impulses derived by the needle tip 25 from the record, and the resulting electromotive forces may be transferred to suitable amplifying apparatus and a loudspeaker through the leads 5. Since the needle 23 is flexible in both a plane normal to the record and a plane parallel with the record, it is obvious that the needle 23 will impart only very slight forces to the record, thereby reducing the generation of the wave motion by the record. Hence, the subsequent radiation of noises such as are characteristic of the prior art phonographs will be almost entirely eliminated.

The improved pick-up device heretofore described is very compact and light in weight and has a needle pressure of from about one-half ounce to one ounce. Because of the flexibilitymf the needle 23, it is advisable to provide additional support for the pick-up device. For this purpose a guard 21 may be secured to the bottom of the casing l. The guard 21 extends forwardly over the needle 23 and is provided with an opening 29 through which the connecting arm 2| extends. At its forward end, the guard is bent downwardly and is bifurcated, as clearly shown in Fig. 5, so

that it is adapted to straddle the needle 23 at substantially the bend therein. Secured to the guard 21 above its bifurcated portion is a plate 3| to the underside of which is secured a rubber block 33 which. acts as a bumper for taking up the shock which the pick-up may receive when accidentally dropped onto the record. The bifurcated downwardly extending end of the guard 21 has fixed thereto a secondary or auxiliary guard in the form of a wire 35 which is mounted slighlty behind the needle tip 25 and beneath the major portion of the needle 23, the guard wire 35 preventing the needle tip 25 from being accidentally bent back out of place, since the needle tip 25 projects down below the bifurcated extension of the guard 21 only a very short distance. During reproduction, as the needle tip 25 rests on the record, the needle is spaced slightly vfrom the guard 35 and engages the rubber bumper 33, as clearly shown in Fig. 5. Thus, the rubber bumper 33 is also adapted to act as a bearing for the needle 23.

Although I have shown and described but one embodiment of my invention, I am fully aware that many other modifications thereof are possible. For example, instead of removably mount-' ing the arm 2| in the torsion member 9, it may be fixed thereto and made a permanent part thereof. Also, it will be obvious to those skilled in the art that my improved needle is not necessarily limited to use with a crystal pick-up, but may be used with a pick-up or generator of the electromagnetic, dynamic, condenser or any other suitable type. Furthermore, if it is desired, the bumper 33 may be made of any other suitable material than rubber, or it may even be dispensed with entirely. Also, if desired, the major, hori zontal portion of the needle 23 may be made of piano wire and the downwardly extending needle tip 25 may be made of tungsten or other wearresistant metal and welded, or otherwise suitably operate with a phonograph record, the combination of an oscillatably mounted yoke member having a free end, a rigid arm secured to said yoke member adjacent the free end thereof, and a thin needle formed of wire secured to said am and extending forwardly thereof, said needle having a bend therein adjacent its free end to provide an ofiset needle tip adapted to track the record groove, and said needle being substantially rigid torsionally whereby it is adapted to oscillate' said yoke member but being flexible in planes both parallel with and normal to the cooperating record. 7

2. The invention set forth in claim 1 characterized in that said arm is removably received by said yoke member.

3. A phonograph needle comprising a member having a relatively elongated, flexible portion which is substantially rigid torsionally but flexible in all directions in a plane normal thereto, and a relatively short portion integral with and extending at an angle to said first-named portion and constituting a record-engaging tip, said elongated portion being mounted to move arcuately as a whole in-response to lateral actuation of said tip portion by a record.

4. A phonograph needle for cooperation with a record having a laterally undulating groove comprising a member having a. relatively elongated. flexible portion which is substantially rigid torsionally but flexible in all directions in a plane normal thereto, and a relatively short portion extending from said first-named portion at substantially a right angle thereto, said short portion constituting a record-engaging tip'adapted to be actuated by the undulations or th groove and to transmit the undulatory movement thereof to said first-named portion to cause said first named portion to move arcuately as a whole in correspondence with said undulations by reason of the torsional rigidity of said first-named portion.

5. A phonograph needle according to claim 4 characterized in that said first-named portion is constituted by a metallic wire having a diameter of approximately 0.006" to approximately 0.010".

6. A phonograph record according to claim 4 characterized in that said first-named portion has a length of the order or /4" and said secondnamed portion has a length or the order of $6 5.

HAROLD J. HASBROUCK, JR.

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