US2254732A

US2254732A - Tone arm

Info

Publication number: US2254732A
Application number: US332202A
Authority: US
Inventors: Dally Roy
Original assignee: Webster Electric Co Inc
Current assignee: Webster Electric Co Inc
Priority date: 1940-04-29
Filing date: 1940-04-29
Publication date: 1941-09-02
Anticipated expiration: 1958-09-02

Description

R. DALLY Sept. 42, 1941.

TONE ARM Filed April 29, 1940 WKNNJ /M LW z/y Nw mi e@ a ,@N, Y. @2^ y NNI Patented Sept. 2,1941

TONE ARM Roy Daily, Racine, Wis., assignor to Webster Electric Company, Racine, Wis., a corporation of Delaware Applicationnprn 29,1940, semina. ssazczf '7 Claims.

The present invention relates to tone arms and is particularly concerned with improved 'constructions of the tone arm and the supporting arrangements whereby the tone arm is secured to a fixed support for engagement with a record on a turntable.

One of the objects of the invention is the provision of an improved tone arm adapted to beused for sound reproduction apparatus -oi high on the phonograph, to such a position that the Y bottom of the pickup can be inspected and the needle can be most conveniently inserted.

Another .object of the invention is the provision of an improved tone arm support having a resilient connection between the tone arm and the support so that the tone arm can be removed at any time by merely springing apartv the bearing springs which are carried by one of'these parts.

Another object of the invention is the prol vision of an improved tone arm supporting structure by means of which undesirable vibrational characteristics of the tone arm or needle noise may be absorbed to prevent the transmission of undesirable vibrations to the stylus of the needle and the pickup device carried by the tone arm.

Another object of the invention `is the provision of an improved construction for supporting a tone arm, by means of which the tone arm is permitted to vibrate as a unit,` thus reducing the resonant frequency characteristics which are present whenever an arm vibrates in torsion.

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

Referring to the single sheet of drawings accompanying this specification:

Fig. k1 is a fragmentary plan view of a phonograph'installation showing the relation of the tone arm and the record on the turntable;

Fig. 2 is a full size vertical sectional view taken on the planeof the line 2--2 of Fig. 1 looking in the direction of the' arrows, partially broken away to show the interior structure of the tone i arm support;

Fig. 3 is another fragmentary vertical sectional viewtaken on the plane of the line 3 3 of Fig. 2 looking in the direction of the arrows; and

Fig. 4 is a fragmentary horizontal sectional view taken on the plane of the line of Fig. 2.

Referring to Figs. 1 and 2, il) indicates the supporting structure of a phonograph which is provided with the usual turntable indicated at il carrying the phonograph record disc i2. I3 indicates a tone arm constructed according to the present invention and supported upon the base il! for substantially universal pivotal movement, in order that it may be raised from or lowered to the record and in order -that it may move horizontally across the face of the record as the playing of the record progresses. The base i0 is preferably provided with a special tone arm support it located at one side of the turntable il and adapted to support the tone arm wooden screw. I6 and having a vertically extending column Il. The top of the column Il 'is provided with a substantially V-shaped notch I8 adapted to receive the stem ISof a headed mem'- ber 2G carried :by the side of thetone arm.

The headed member 20 has its stem I9 provided with rivetedformations inside and outside the adjacent wall 2l of the tone arm I3. The supporting post 22 for the tone arm is preferably lso located with respect to the stylus 23 and with respect to the direction Ain which the stylus points, that there is substantially tangential.

be chamfered atl 21, leaving only an annularthrust surface 28 of reduced area for permitting rotation with a minimum amount of friction.

The lower end of the post 22 ispreferably of reduced diameter and threaded at 29, leaving an annular shoulder 36 for engagement with a washer or thrust plate 3|. The. post 22 may be secured to the wooden base l by means of another washer 32 and a nut 33 which clamps the board I0 between the washers 3| and 32. supporting post 22 rotatably supports a hollow shaft 35 which comprises a cylindrical tubular brass member, the bore of which is utilized to pass the

conductors

36 and 31 which lead to the pickup unit 38.

Tubular shaft 35 may be provided at its lower end with an annular groove 40 (Fig. 3) of substantially semi-circular cross-section adapted to receive the spring wire 4| which ts in the groove 40 and forms a thrust bearing for the lower end of the shaft 35 to retain the shaft in the post 22. That part of the spring wire 4I which projects from the groove 40 engages the annular thrust surface 42 on the lower end of the post 22 when the shaft 35 is actually subjected to any lifting force. As a matter of actual practice, this would only occur when the phonograph were turned upside down or subjected to unusual movements and thus the toneI arm customarily rests upon the thrust surface 28 and the wire 4I serves the purpose of maintaining the parts in permanent assembly.

The upper end of the tubular shaft 35 is preferably subjected to an upsetting operation which produces an annular rib 45 having the upper and lower substantially flat surfaces 46 and 41. The surface 46 serves as a thrust bearing engaging the bearing surface 28 on the post 22. The tubular shaft. 35 is also preferably formed with a partially spherical protuberance 48 immediately above the flange 45 and after assembly with the cushion member 49, it is also formed with an outwardly spun ange 50 outside a metallic washer 5|. The cushion member 49 preferably consists of a soft resilient annular member having, before its assembly with the parts of Figure 3, a cylindrical through-bore 55. It also has the substantially flat end surfaces 56 and 51 and its outer surface may be substantially circular in cross-section at 58, 59. The annular cushion member 49 is provided with an annular groove 66 of substantially rectangular cross-section located in its periphery midway between the ends 56, 51, and adapted to receive the adjacent parts of a metal pintle plate 6I.

The pintle plate 6| is shown in Figure 4 and. Figure 2. It comprises a relatively thick sheet metal member, the main body of which is substantially rectangular in shape, being provided with the substantially straight edges 62, 63 and with a substantially circular end boundary 64. At its opposite end, it tapers inward at 65 and 66 and the relatively narrow end portion 61 is bent upward at 66. The extreme end 69 of this pintleplate is adapted to serve as a stop for engaging inside the upper wall 10 of the tone arm I3 to prevent the stylus 23 from `engaging the base I0 when the tone arm is at one side of the record. This is, of course, also prevented by the supporting column I1 when the tone arm is on the supporting column.

The pintle plate 6| has at one end (the right end in Figure 4) a circular aperture 1| which isvslightly smaller than the diameter of the base 12 of the groove 66 in the cushion member 49.

The thickness of the plate II is substantially the same as the width of the groove 60.

Thus, the cushion member 49 may be placed CTI inside the aperture 1| in such manner that its flanges 1 3 and 14 are located below and above the pintle plate 6I. The cushion member 49 and the pintle plate 6| may then be placed upon the partially spherical formation 48 of the tubular shaft and secured in place by means of the washer 5I which is held in place by the spun formation 50. The space between the washer 5I and the flange 45 is such that the cushion member 49 is placed under a predetermined compression so that the pintle plate is resiliently gripped by the cushion member 49 and the cush ion member 49 also resiliently grips the partially spherical formation 48 on the shaft 35. The relation of all the parts surrounding the cushion member 49 is such that the cushion is placed under compression and the pintle isresiliently supported upon the shaft 35 but out of all metallic contact with the shaft.

The pintle plate 6| is provided with a pair of laterally projecting portions 16, 11 which are also subjected to an upsetting operation for the purpose of forming the substantially frusto-conical pintle surfaces 18. These pintle surfaces bear such a relation to the bearing apertures 19, one of which is located in each wall 2| or 80 of the tone arm, that each aperture receives one of the pintles 16, 11.

The cushion member 49 also supports the tone i arm in such manner that it is permitted to vibrate as a unit. This reduces the resonant frequency characteristics of the tone arm which are present whenever a tone arm is vibrated in torsion.

The size of the apertures 19 is such that the inner edge of each aperture engages on the' frusto-conical wall 18 of the pintles 16, 11. The length of the pintle plate 6| axially of the pintles 16, 11 is such that the side walls 2| and 86 of the tone arm are placed under predetermined tension when the parts are in the position of Figure 3. Furthermore, the two walls 2| and 80 may be forced apart to permit the removal of the pintle plate 6| by producing a disengagement of one or the other of the pintles 11 fromA its aperture 19. Thus the tone arm is removable from the vertical shaft 35 at al1 times. The frusto-conical pintles are adapted to have an annular line contact with the apertures 19 in the tone arm so that they permit movement in a giertical plane with a minimum amount of fric- The tone arm I3 preferably consists of a stamped sheet metal member of channeled form provided with an integral top wall 10 and a pair of parallel side walls 2| and 80. The side walls 2| and 80 are joined by an integral end wall 6| (at the right in Figure 2) and with an integral end wall 82 (at the left end in Figure 2). Referring to Figure 1, the tone arm I3 is preferably provided with a channeled formation I3 extending diagonally backward from the end 32 and terminating in an end wall 84. This channeled formation is for the purpose of receiving and locating a crystal reproducer unit 95 of the type shown in my prior application, Patent No. 2,197,967, issued April 23, 1940, Sound reproducing apparatus, and indicated at |45 in Fig. 8 of that patent, at such an angle to the main body of the tone arm I3 that substantially tangential tracking may be secured. The present tone arm may, however, be used with any type of reproducer unit such as electro-magnetic reproducer units or crystal reproducer units. The crystal unit may be secured in place by means of a pair of angle brackets, onel angle bracket 86 being spot-welded to the top wall of the tone arm and having a downwardly extending iiange 8l and a horizontally extending iiange 88. Anothersimilar angle bracket may have a horizontal nange 88 secured to the flange 88, a side ange Q0, and va horizontal clamping flange 9| which engages the crystal unit 85 and holds it in the tone arm when the

flanges

88, 89 are secured together.`

The conductors 38 and 3i are secured in the channeled tone arm i3 byy their attachment at one end to the crystal unit 85 and at the other end by passing into the hollow shaft 35.' In between these points there may be spot-welded bendable metal clips 92 which may engage and support the conductorsf and 3l. The circuit preferably includes a signal light indicating when the circuit is energized and the light may be exposed through an 'aperture in the tone arm i3 which is covered with 'a transparent button 93 of a phenolic condensation composition.

The cushion member "i9 is preferably made of pure para rubber of soft resilient characteristics or it may be made up out of printers roll composition peculiary adapted to prevent the transmission of undesirable vibrations from the support i@ tothe tone arm I3. The tone arm i3 Abe lifted high enough so thatl the needle aperture may be inspected and the needle most conveniently inserted. The arm supporting structure is simple and adapted to take up wear and to prevent rattling and there is a complete absence of metal-to-metal contact between the y tone arm and its metallic supporting post car-` ried by the base of the phonograph or other device. 1

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 myselfof all changes within the,

scope of the appended claims. y

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

1. In a tone arm, the combination of a support with a bearing member extending transversely to said support, a shaftv rotatably mount ed in said bearing member and having means at each end retaining it in said bearing member, a resilient cushion member carried by said shaft, a'pintle plate carried by said cushion member and having oppositely extending trunnions, and a tone arm having bearings engaging said trunnions, whereby said tone arm is supported for substantially universal movement on said supf port, said cushion member absorbing and proto said support, a shaft rotatably mounted in said bearing member and having means at each end retaining. it in said bearing member, a resilient cushion member carried by said shaft, a pintle plate carried by said cushion member and having oppositely extending trunnions, and a tone arm having hearings engaging said trunnions, whereby said tone arm is supported for substantially universal movement on said sup. port, said cushionmember absorbing and preventing transmission of undesirable vibrations from said support to said tone arm, a pair of annular compression members carried by said shaft, said cushion member comprising a soft, resilient, annular rubber member compressed between said two annular compression members on said shaft and having a peripherally located annular groove for receiving the adjacent parts of said pintle plate.

43. In a tone arm, the combination of a support with a metallic bearing member having a cylindrical bore and a reduced threaded cylindrical portion with thrust members carried at each end of said threaded portion and threaded means whereby the bearing may be clamped on the support, a tubular shaft member rotatably mounted in said cylindrical bore in said bearing, removable means at one end of said shaft for retaining it in said bearing, an annular flange carried by said shaft at the other end of said bearing, said bearing having a reduced annular thrust surface engaging said ange, a ,thrust member,a resilient rubber cushion member of annular shape clamped between said nange and said thrust member carried by the end of said shaft, a pintle plate carried by said cushion member, and a tone arm carried by said pintle plate for pivotal movement, said cushion member having an annular groove formed in its periphery and said pintle plate having an aperture of a size adapted to receive that portion of the cushion member at the base of said groove.

4. In a tone arm, the combination of a support with a metallic bearing member having `a cylindrical bore and a reduced threaded 'cylindrical portion with thrust members carried at each end of said threaded portion and threaded means whereby the bearing may be clamped on the support, a tubular shaft member rotatably mounted in said cylindrical bore in said bearing, removable means at one end of said shaft for retaining it in said bearing, an annular nange carried by said shaft at the other endof said, bearing, said bearing having a reduced annular thrust surface engaging said flange, a thrust member, a resilient rubber cushion member of annular shape clamped ybetween said nange and said thrust member carried by the end of said shaft, a pintle plate carried by said cushion member, and a tone arm carried by said pintle plate for pivotal movement, said cushion member having an annular groove formed in its periphery and said pintle plate having an aperture of a size adapted to receive that to a predetermined compression for the purpose of preventing transmission of predetermined vithrough bore, said tubular metal member being tween said two annular compression members on f with a bearing member extending transversely brations from said bearing to said tone arm.

5. A mounting for tone arms comprising a tubular metal member having an axially extending formed on one end with an annular shoulder and a reduced threaded portion, threaded means carried by said reduced threaded' portion' for clamping the said tubular metal member on a support,

said tubular metal member having thrust bearing surfaces at each of its ends, a tubular shaft rotatably mounted in said through bore and having means at its lower end for engaging the adjacent thrust surface on said tubular metal member, said tubular metal shaft having an annular thrust flange projecting at substantially right angles to its axis and located at the upper end of said tubular metal member, a live resilient rubber bushing member carried by the upper end of said tubular shaft and having an annular groove located in its periphery, a compression member carried above said cushion member, said tubular shaft being spun outwardly to retain said compression member, and a pintle plate located in said annular groove, said pintle plate having oppositely projecting pintles with frusto-conical bearing surfaces located thereon. Y

6. A mounting for tone arms comprising a tubular metal member having an axially extending through bore, said tubular metal member being formed on one end with an annular shoulder and a reduced threaded portion, threaded means carried by said reduced threaded portion for clamping the said tubular metal member on a support, said tubular metal member having thrust bearing surfaces at each of its ends, a tubular shaft rotatably mounted in said through bore and having means at its lower end for engaging the adjacent thrust surface on said tubular metal member, said tubular metal shaft having an annular thrust flange projecting at substantially right angles to its axis and located at the upper end of said tubular metal member, a live resilient rubber bushing member` carried by the upper end of said tubular shaft and having an annular groove located in its periphery, a compression member carried above said cushion member, said tubular shaft being spun outwardly to retain said 4compression member, and a pintle plate located in said annular groove, said pintle plate having oppositely projecting pintles with frusta-conical bearing surfaces located thereon, said live resilient cushion member being placed under a predetermined state of compression between said thrust flange and said compression member whereby the pintle plate is resiliently clamped between the'walls of said groove.

7. In a tone arm, the combination of a supporting post with a shaft rotatably mounted in said shaft, said shaft having laterally projecting and oppositely disposed trunnions carried by its upper end and a channelled tone arm, said tone arm having downwardly projecting flanges on each side, said anges being provided adjacent one end of the tone arm with apertures for receiving said trunnions, and said tone arm being formed at its free end with a diagonally extending housing portion, and a reproducer member located in said diagonally extending housing portion, said housing portion and reproducer being arranged at such an angle that there is substantially tangential tracking of the needle carried by the reproducer in the grooves of the record substantially midway between the beginning and end groove of the record.

ROY DALLY.