US2320416A - Stylus for reproducers - Google Patents

Description

June 1, R DALI-Y S'I YLUS FOR REPRODUCERS Filed June 23, 1941 3 Sheets-Sheet 1 30a; 3 23 jg 16 3 Sheets-Sheet 2 R. DALLY STYLUS FOR REPRODUCERS Filed June 25, 1941 June 1, 1943.

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STYLUS FOR REPRODUCERS Filed June 25, 1941 s Sheets-SheetS I20 den/Z01" Patented June 1, 1943 UNITED STATES PATENT OFFICE STYLUS FOR REPRODUCERS Roy Dally, Racine, Wis., assignor to Webster Electric Company, Racine, Wis., a corporation of Delaware Application June 23, 1941, Serial No. 399,257

3 Claims. (01. 274-38) sion of an improved stylus for reproducers which is adapted to have a shock absorbing action for the purpose of protecting the point or engaging part of the stylus which may be a stone subject to chipping when it is dropped or struck upon a hard surface.

Another object of the invention is the provision of an improved stylus which has a controlled vertical and a controlled torsional compliance for the purpose of assisting in the tracking of the stylus in the groove, but which also has a controlled longitudinal compliance.

Another object of the invention is the provision of an improved reproducer arrangement including an improved stylus 'which is adapted to secure good tracking irrespective of the angle at which the reproducer is set with respect to the tangent to the groove so that it is not necessary to use an angular tone arm.

Another object of the invention is the provision of an improved reproducer which is adapted to track properly at extremely low needle pressures such as 1 ounce or less as compared to 2, 3, 4 or 5 ounces needle pressure.

Another object of the invention is the provision of an improved stylus structure having a resilient action to facilitate good tracking at extremely low needle pressures in which the fatigue of the parts is reduced to a minimum so that the stylus may beused for a long period of time without replacement,

Another object of the invention is the provision of an improved stylus for reproducers which ,1

i adapted to be used on reproducers of the generator or modulator type such as electrostatic reproducers, magnetic reproducers, crystal reproducers, or those of the resistor type.

Another object of the invention is the provision of an improved crystal pick-up assembly which is adapted to reproduce with improved fidelity over the reproduced range and adapted to be used for a long period of time without necessity for repair or readjustment.

Another object of the invention is the provision of an improved crystal pick-up unit assembly which may be manufactured very economically and which may thus be placed within the means of a larger number of purchasers.

I Another object of the invention is the provision of an improvement of tone quality of phonograph pick-ups, the reduction of record wear,

and the reduction of mechanical noise of phonograph pick-ups.

Another object of the invention is the provision of an improved assembly, including one of the standard types of phonograph pick-ups, by means of which it is possibleto obtain the benefits of a protected permanent or semi-permanent point and the increased compliance of light weight pick-up tracking.

Another object of the invention is the provision of an improved stylus assembly which has a controlled vertical compliance so that the stylus point can follow the constantly changing width of record grooves without causing a like motion of the reproducer, thus providing better tracking of the record grooves than with the devices of the prior art.

Another object of the invention is the provision of an improved stylu assembly, including a resilient member which is properly portioned in width, length, and thickness, to predetermine the ratio between the increased lateral compliance of the reproducer, which is due to the increased length of the mechanical path from the stylus point to the pick-up mechanism, and the vertical compliance which is necessary to provide proper tracking of the stylus point in the record groove.

Another object of the invention is the provi- Another object of the invention is the provision of an improved stylus assembly, which is provided with damping means for damping out undesirable characteristics of the assembly.

Other objects and advantages of the invention will be apparent from the following description and accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings, of which there are three sheets:

Fig. 1 is a top planview of a reproducing phonograph equipped with the tone arm according to the present invention;

Fig. 2 is a fragmentary vertical sectional view taken through the magnetic pick-up tone arm equipped with a stylus constructed according to the invention;

Fig. 3 is a view similar 'to Fig. 2, showing a crystal pick-up equipped with a stylus according to the invention;

Fig. 4 is a side elevational view in partial section, the section being on the axis of the shank, showing the structure of a stylus constructed according to the invention;

Fig. 5 is a sectional view taken on the plane of the line 5-5 of Fig. 4, looking in the direction of the arrows; and I Fig. 6 is an enlarged fragmentary sectional view of the tracking end of the stylus shown in connection with a groove;

Fig. 7 is a view similar to Fig. 4 of a modified form of stylus, in which the resilient member is provided with wave-like corrugations for controlling the torsional compliance;

Fig. 8 is a view similar to Figs. 4 and 7 of another modification, in which the stylus is provided with means for damping out undesirable vibrational characteristics;

Fig. 9 is another similar view, in partial section, of a modification provided with a metal point;

Fig. 10 is a fragmentary sectional view of the point structure of Figs. 7 or 8;

Fig. 11 is a fragmentary sectional view, taken on the plane of the line of Fig. 10;

Fig. 12 is a plan view of the resilient member, preferably employed in the modifications of Figs. 7 to 9.

Referring to Figure 1, l0 indicates a support which is provided with the usual turntable II for supporting the record i2 provided with the spiral record groove l3. The tone arm l4 may comprise a downwardly opening channelled member of metal or .molded phenolic condensation compound, closed at both ends and supported at its .upper end in Figure 1 by a supporting column l5 carried on the support Ill.

The column I5 is provided with some form of universal connection for supporting the tone arm l4, whereby the tone arm may be lifted from the record or it may move laterally of the record in following the grooves of the record. At'its free end, that is the lower end of Figure 1, the tone arm |4 houses andsupports a pick-up which may be of the electrostatic, magnetic, crystal or resistance type. The housing is provided by a horizontal plate I 6 having an angular flange t1 and pick-up may be secured in place by a screw bolt |8. At its free end the tone arm has an aperture for passing the stylus screw 30 which serves ,to clamp the stylus in the chuck of the pick-up.

In Figure 2 the tone arm is shown equipped with a magnetic pick-up comprising a chuck 2|] having its trunnions 2 |22 provided with rubber sleeves 23-24, adapted to be received in complementary bearings carried between the pole pieces of a permanent magnet 25.

The chuck is of magnetic material and is provided with an armature 26, preferably surrounded with soft resilient material such as rubber, and located between the two pole pieces ,of the permanent magnet 25 for vibrations responsive to the movements of the chuck 28,

screw bolts 5|52.

larged in Figures 2 and 3, is enlarged still fur- The upper part of the armature is surrounded by the coils 21, in which an electromotive force is generated when the lines of flux between the poles of the permanent magnet 25 cut the coils, due to the movement of the armature. The chuck 20 is provided with a downwardly open bore 28, which intersects the horizontal threaded bore 29. The bore 28 usually has an inclination from the vertical toward the direction in which the record is moving, to facilitate the tracking of the ordinary type of stylus, and bore 28 is adapted to receive the shank of a stylus.

Threaded bore 23 is adapted to receive the hardened stylus clamping screw '38, which is threaded to fit this bore, and has a knurled head 3| to be engaged by the fingers. The reproducer of Fig. 2 is provided with an improved stylus 3|,

.having a shank 32, a spring arm- 33, and a point 34, preferably supported by a metal body 35. This stylus will be described in detail hereinafter.

Referring to Fig. 3, this view shows a crystal pick-up, comprising a pair of half housing members 36, provided with bearings 31-38 for receiving the trunnions of a chuck 39. In this case the chuck has its trunnions 40- again provided with the resilient rubber tubes 42-43, which are compressed in the bearing bores'31-38. The chuck again has a downwardly open bore 28 for receiving the shank 32 of the stylus 3|, the

shank being clamped by means of the stylus screw 30.

The end of the chuck opposite to the screw 38 is provided with a clampingplate 44 secured to the chuck by screw bolt 45, so that the crystal assembly 46 may be clamped to the chuck. Layers of foil are arranged outside each of the crystals, and they may be connected in series or parallel to the conductors 41-48, which are secured to connectors 48-49, carried by an insulating block 58.

The housing is composed by securing two halves of the housing 38 together by means of The stylus 3| which is enther in Figures 4, 5 and 6 for the purpose of showing its structure more clearly. The shank 32 is preferably of relatively soft metal such as brass, duraluminum or aluminum, so that when the screw engages it the point of the needle,

which is usually made harder, may dent the shank and hold it more firmly against rotation. Shank 32 is preferably cylindrical in form being made out of a small rod or a wire, but it is preferably provided with a flattened portion 53 extending along its forward side at the top for a sufllcient distance to insure the engagement of this flattened portion 53 with the pointed end of the clamping screw 30.

The lower end of the shank 32 is preferably provided with a shoulder 54 for engaging the upper surface 55 of the spring 33 and the shank is preferably provided with a portion 58 of reduced size for engagement in an aperture 51 in the right end of the spring 33. The reduced portion 58 is preferably non-circular in form and may be made of the shape shown in Figure 5 indicated by the numeral 56, where this part is shown to be oval and cylindrical at the right hand side but formed somewhat like a knife edge at the opposite or left hand side. In any event, the reduced portion 56 fits in an aperture 51,0f complementary shape and the lower endof the stylus is riveted over at 58 to secure the spring firmly on the reduced portion 56 between the riveted part 58 and the shoulder 54. Thus the spring 33' is fix- Another reason for the ofiset at 14 is to peredly secured against rotation on the shank 32. It projects laterally from the shank on the same side on which the flattened portion 53 is located. At its opposite end the spring 33 is provided with an aperture 53, which may be circular, which is adapted to receive the reduced cylindrical portion 60 of the metal body 35. This metal body 35 may be secured in the aperture 53 by riveting over the upper end 61 of the metal body. The spring 33 is then clamped between the annular shoulder 62 and the riveted portion Ill. The metal body 35 preferably comprises a tiny rod of brass, aluminum or duraluminum, bronze or stainless steel. It is provided with a drilled axial bore 63 which is open at its lower end and adapted to receive a stone 34 which is provided with a blunt conical point 64.

This point is shown in greater detail in Figure 6, where it will be observed that the lower end of the point 64 is rounded and the generally conical sides are also curved longitudinally at 66.0n the curve of a large circle. There is a clearance be-- tween the walls 61 and 68 of the groove l3 in the record I! and thesides of the pointed stone 34.

The stone may be secured in the bore 63 by spin- The spring 33 is preferably made of any suitable light and resilient material, such as spring bronze or spring steel or a plastic. The spring is preferably relatively thin in its vertical dimension and comprises an elongatedstrip of the spring metal which is of substantial width as compared with its vertical dimension. The space necessary for securing the metal body 35 to the spring and for securing the spring to the shank 32 also renders it necessary to make the spring of substantial width as shown in Figure 5. In order to bring the riveted end 58 of th stylus up above the record, when the stylus issecured in the chuck at an angle, the spring is bent downwardly at 10 and upwardly again at ll,,the

two end portions 12 and 13 being substantially parallel to each other but being offset by a distance depending upon the length of the part" a between the bends Ill and II.

This ofiset brings the riveted end 58 up above the record without necessitating the elongation of the metal body 35 and point 34 which should 7 be kept as short as possible. The purpose of keeping these parts as short as possible is to reduce the leverage with which the end of the pointed member 34 acts on the spring, as any elongation of this pointed member 34 would increase the leverage and tend to increase the longitudinal compliance of the stylus.

Longitudinal compliance is not desirable and.

mit the riveting of the spring 33 on the shank 32 at right angles or an angle of 90. Diagonal rivetlng to the shank would not be tight because the shank would bend and a tight job of riveting to a rod of this kind is best done at 90.

In some embodiments of the invention if the reproducer were specially construced for use with the stylus of thistype. the shank might extend at right angles to the portion 14, eliminating the bend I0, so that the angular direction of the point 34 would be provided by the bend ll. As the present stylus is preferably constructed to be used with all kinds of reproducers. its shank is disposed at an angle which may vary from 12 to The mode of use of the reproducers equipped with the improved stylus will be evident to one skilled in the art. The voltage output is reduced by the use of the present invention, but the outa put is still ample, as suitable amplifiers are used for amplifying the output.

pliance which permits the point of the member 34 to move in any direction laterally and vertically. The pointed member 34 may have a rotati've motion about an axis which is located somewhere in the members 34 and 35. 7

Referring to Figure 6, with an ordinary stylus of the straight type, there are occasions when the vibrations of large amplitude Will cause the point 64 to bind in the groove l3 due to the With the present invention it is not necessary 'to use an angle mounting of the reproducer on the tone arm to secure tangential tracking because tangential tracking is not necessary The vertical and lateral compliance of the stylus assists in the more perfect tracking of the stylus in the groove. The stylus is more free to follow the'groove, and it can rise up in the groove, if necessary. As distinguished from the customary needle pressures of 2, 3, 4, and 5 ounces, the present stylus construction may be used in any generator or modulator, to track properly at needle pressures as low as 1 ounce or less. This produces less wear on the record and needle, and reduces to a minimum the mechanical noise or mechanical reproduction.

' It should also be understood. however, that the resiliency of the spring may be so arranged that the present stylus construction can be used in heavier pick-up assemblies, although all of the advantages will not be realized by using the customary heavy needle pressures of the prior art. mentioned above.

The reproducer may be so arranged that the pointed end of this stylus is adapted to recede into a recess when undue force is appl ed to the point, thus protecting the point of the stylus.

In any event, the spring has a shock absorbing action which will protect the stone against chipping when the tone arm is dropped and the pointof the stylus engages the record or some other part. v

Referring to Fig. '7, this is a view similar to Fig. 4 of a modification of slightly different structure. In this case the shank I5 is of similar 80, comprising an upwardly turned extension on the rear side of the shank 15, which is adapted to receive the shock when the rest of the resilient member l8is bent upward, and the stylus engages some rigid support.

The resilient member" is again made of a tapered metal strip, as shown in plan-in Fig. 12; and it is preferably provided with a plurality of wave-like upward and downward corrugations 81-84, located in the offset portion between the shank-engaging portion 85 and the point-supporting portion 88.

These corrugations control the twisting of the resilient arm 18 and effectively stiffen the arm against twisting too easily. The number of corrugations is chosen or balanced to give the desired vertical compliance and the desired torsional compliance. For example, a flat spring may have its cut-off. at approximately 2,500 cycles, and a corrugated spring of similar size and thickness may have its cut-off at 6,000 cycles. It is thus evident that the corrugations are adapted to be used for effecting a controlled vertical and torsional compliance.

The resilient member 18 is bent downward at 81 and upward at 88 so that the point-supporting portion 86 extends at a suitable angle to give the "point the desired angle for following the record groove.

In some embodiments of the invention this point-supporting portion 86 may be parallel to the record, as the point may not need to be supported at an angle when it is adapted to have the controlled vertical compliance which is present in this device. V

The corrugations 8l84 give the resiliently supported stylus a controlled torsional compliance which represents an improvement over the type shown in Fig. 4. The record engaging point 89 may comprise a sapphire or a metal point or a point made of any suitable alloy or synthetic material. When a sapphire or other non-metallic point is used, it may consist of a substantially cylindrical body 90 provided with a conical point'9l, the extreme point 92 of which is rounded, as shown in Fig. 4.

The cylindrical body 90 has a tight frictional fit in a metal sleeve 93, which in turn is receivedin a circular bore 94 in the resilient member 18.

A radially extending flange 95 on the sleeve 93 provides an annular shoulder 96, which determines the position of the sleeve 93 in the bore 90. The flange 95 is preferably provided with a frusto-conical exterior surface 91.

Referring to Fig. 8, this is a modification similar to Fig. '7, except that its resilient member is provided with damping means. This damping means may comprise a resilient strip 98 of rubber, gelatin, or printer's mold composition, but is preferably of Viscaloid. ited in its elasticity. It is adapted to-stretch, but has a slow return. It is elastic at low frequencies and relatively stifi at high-frequencies. It stifiens the spring against torsion and dampens out the natural resonance of the spring assembly. It is cemented, or otherwise secured to the resilient arm 18, preferably on its upper side, in such manner that it engages the corrugated portions and grooves 8|, 83.

Another form of damping means may comprise a tube of the same material, which is slid endwise on the resilient arm 18 and frictionally engaged by the corrugations 81-84.

Referring to Fig. 9, this is another modification, in which the resilient arm 18 may be of the same construction as shown in Figs. 7 and 8, except that its record-engaging point 99 is made of metal, wood, or synthetic material adapted to be fixedly secured in the aperture I00 of the point-supporting portion 86 by riveting, molding, or cementing.

In this case the conical point has an annular shoulder l0! below the resilient arm 18, and the part I02 engaging the top of the arm may comprise a riveted portion, an integral portion molded to engage the arm when the point 99 is molded, or a body of cement adhering to the end of the pointed member 99 and securing it to the arm.

All of these forms of stylus are adapted to improve the tone quality of phonograph pick-ups and to reduce record wear. They may be used in all types of pick-ups by virtue of the provision of the standard form of shank, and they are adapted to reduce the mechanical noise of the pick-up.

The present stylus has thev advantage of providing a protected permanent or semi-permanent point and a controlled vertical and horizontal compliance so that it may be used with light weight pick-ups at much lower needle pressures than those used in the prior art.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States,v is:

1. A resilient stylus adapted to be protected against shock, comprising an elongated shank adapted to be secured in the chuck of a reproducer, a laterally projecting resilient sheet metal arm fixedly secured in direct mechanical connection with the lower end of said shank, and a pointed member carried by the other end of said resilient arm and projecting downwardly therefrom below the end of said shank when supported in a chuck, and a shock receiving extension of said arm carried by said arm and pro jecting backwardly from said shank and having an upwardly curved portion adapted .to engage any support when a reproducer is dropped hearing said stylus, the resilient arm having sufficient flexibility to permit the pointed member to be flexed upwardly so that said shock-engaging portion will bear the shock.

2. A stylus for reproducers, comprising a metal shank adapted to be secured in the chuck of a reproducer, said shank having at its outer end a laterally projecting resilient arm fixedly secured This material is limsaid arm and extending longitudinally thereof.

3. A stylus for reproducers, comprising a metal shank adapted to be secured in the chuck of a reproducer, said shank having at its outer end a laterally projecting resilient arm fixedly secured to said shank, said arm being provided at its free end with a pointed member adapted to engage in a record groove, said arm extending backwardly with respect to said shank, away from said pointed member, to provide a supporting "member for receiving the shock when thearm is bent upward by a shock. I

4, A stylus for reproducers, comprising'a metal shank adaptedrto be secured to the chuck of a reproducer, said shank having at its lower end.

a resilient arm comprising a strip of metal riveted to said shank, said arm being tapered toward its free end and having at its tree end a pointed member fixedly secured thereto for engagement with the groove of a record; and said arm having intermediate the shank and pointed member a plurality of transverse corrugations for controlling the torsional icompliance, and a ,damping strip of deformable andpartially resilient material secured to said arm. and ex-' tending in contacting engagement with said arm alongthe corrugated. portionof the arm.

7 a 5. A stylus for reproducers, comprising a metal shank adapted to be secured in the chuck of a reproducer, said shank having its lower end fixedly secured in direct metallic connection to a thin resilient sheet metal spring am, said arm extending in a generally diagonal direction laterally and downwardly with respect to the axis of said shank and having a point supporting portion extending upwardly at, a slight angle to the record when in record-engaging position, and a pointed record engaging member fixedly secured to said point supporting portion, and

adapted to be flexibly and resiliently supported by said shank through the intermediary of said arm whereby the pointed member has improved vertical compliance for use at relatively low needle pressures, said diagonally extending portion being provided with a transverse corrugation for increasing the torsional compliance of the pointed member of said stylus to effect a substantial reduction of binding of the pointed member in the record groove.

7. A stylus for reproducers, comprising a metal shank adapted to be'secured in the chuck of a reproducer, said shank having its lower end fixedly secured in direct metallic connection to a thin resilient sheet metal spring arm, said arm extending in a generally diagonal direction laterally and downwardly with respect to the axis of said shank and having a point support- 1 i g portion extending upwardly at a slight angle a. thin resilient sheet metal spring arm, said arm extending in a generallydiagonal direction laterally and downwardly with respect to the axis of said shank and having a point supporting portion extending upwardly at a slight angle to the record when in record-engaging position, and a pointed record engaging member fixedly secured to said point supporting portion, and adapted to be flexibly and resiliently supported by said shank through the intermediary or said am whereby the pointed member has improved vertical compliance for use at relatively low needle pressures, said resilient sheet metal arm having a rearwardly and downwardly extendin short and relatively stifl upwardly curved shock arm adapted to engage any support and take the shock when a tone arm bearing said stylus is dropped, the pointed member flexing upwardly lay/virtue of the flexlblelresiliency of said firstmentioned arm.

6. A stylus for reproducers, comprising a metal fixedly secured in direct metallic connection to respect to the groove of the record.

to the record when in record-engaging position, and a pointed record engaging member fixedly secured to said point supporting portion, and adapted to be flexibly and resiliently supported by said shank through the intermediary of said arm whereby the pointed member has improved vertical compliance for use at relatively low needle pressures, said diagonally extending portion being provided with transverse corrugations for increasing the torsional compliance of the pointed member of said stylus to effect a substantial reduction of binding of the pointed member in the record groove, and the corrugated portion of said resilient sheet metal arm having a layer of vibration absorbing damping material secured to it and extending over predetermined of said corrugations.

8. A stylus for reproducers, comprising a metal shank adapted to be secured in the chuck of a reproducer, said shank having its lower end fixedly secured in direct metallic connection to a thin resilient sheet metal spring arm extending substantially normal to said shank, and a pointed member carried by the other end portion of said arm and extending substantially normal to said latter end portion, said pointed member being adapted to engage the record and to track in the groove thereof, said spring arm having reverse curves intermediate its ends and having a greater width than its thickness, whereby said spring arm is adapted to permit a greater vertical compliance of the pointed member with ROY DALLY.

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