US2363655A

US2363655A - Tone arm

Info

Publication number: US2363655A
Application number: US464201A
Authority: US
Inventors: Dally Roy
Original assignee: Webster Electric Co Inc
Current assignee: Webster Electric Co Inc
Priority date: 1942-11-02
Filing date: 1942-11-02
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

R. DALLY worm ABM Nov. 28, 1944.

Filed Nov. 2," 1942 Z01? ZOZ Ja PatentedNov.28,1944 w 1. 2.363 655 UNITED STATES P TENT OFFICE;

Electric Company, Racine, Wis., a corporation of Delaware 7. l

Application November 2, 1942. Serial No. 464,201

" 1 Claim; (01. 2v4-2s)- 1 V, .1

The present invention relates to tone arms, Fig.4 is afraginentary sectional view, taken on and is particularly concerned with an improved the horizontal plane of the lined-6 of Fig. 3, structure for pivotally supporting the tone arm lookingin thedirection or the arrows. for a limited universal movement. Referring to Fig. 1, 20 indicates the fixed sup- Another object of the inventionis the provi- 5 port for the tone arm 2| and the turntable 22 in sion of an improved tone arm construction the form of the top panel of a phonograph or adapted to be used for sound reproducing appa other housing. The tone arm, which is indicated ratus of high fidelity and which is adaptedto be 1 in its entirety'by the numeral 2|, includes a piv-' used with conventional phonographs to give the otal supporting. member 23 by means of which best reproduction and minimum record wear, and the tone arm is (mounted for substantially unito eliminate undesirable frequency responses. versal movement so that it can be lifted from Another object of the invention is the provision the record and so that it can progress across the of an improved light tone arm and reproducer record as its needle follows the groove in the unit structure in which the characteristics of in-. record 24. v v l ertia and weight may be conveniently adjusted The t ca m s p r y of & C nn to any desired value. struction, having an upper wall 25 (Fig. 3) and Another object of the invention is the provision v a pai 01 d p d ng side walls ZBand 21 join d by of an improved form of tone arm pivotal support the partially cylindrical corner portions 28. At by means of which the tone arm may be so its rear or pivotally supported end, it has an end mounted that it can be lifted up when install d wall 29, closing the end of the channel and joined on the phonograph to such position that the 0 p y a pa a y Cylindrical D bottom of the pickup can be inspected and the tion 3 V needle most conveniently inserted. The width of the top wall and of the channeled Another object of the invention is the prdviarm preferably increases somewhat from its rear sion of an improved tone arm support having a end toward the free or reproducer end, and the resilient connection between the'tone arm and channelpreferably has an enlargement at its support so that thetone arm can be removed at reproducer end, as shown in Fig. 2. Atthis end any time by. merely springing apart the pintle the side wall 21 is inte-grallyjoined to a side wall supporting springs which are carried by th'itone portion 3|, which extends outward at an angle .arm support and by means of which anywear and is joined to a side wall portion 32, which may be takenup so that there is no possibility extends diagonally down toward the other end of rattling. wall 33 of the channeled arm. The side wall 26 I Another object of the invention is the provision may extend in substantially the same direction of an improved tone arm and reproducer unit throughout its fulllength to the point where it which may be manufactured more economically 3 joins the end wall 33.

than the devices of the prior art, which maybe .All of these side wall portions are joined to assembled with less labor, and which requires 9. their respective end wall or other side wall porlesser number of'parts. tions by the

curved corner walls

34, 35, 36, as in, Other objects and advantages otthe invention dicated in Fig. 2; and the walls of the enlargewill be apparent from the following description ment, which is indicated in its entirety -by the and the accompanying drawing, inwhich similar numeral 31, are preferably slightly deeper than characters of reference indicate the same parts the rest of the tone a'rmso that the enlargement throughout the several views, 1 w forms a housing 38 which is of greater depth than Referring to the single sheet of drawings acthat portion of the arm which extends backward companyingthis specification, from it.

' Fig. 1 is a top plan view of atone arm and The enlargement 31 may be provided on its side turntable installation embodying. the present inwalls and top wall 39 with a plurality of transvention; versely extending reenforcing ribs 40 (Fig. 1) ex- Fig. 2 is a full sized bottom plan view of the tending from the bottomof each wall up over the tone arm removed from its pivotalsupport; top of the arm and down the other side. Fig. 3 is a fragmentary elevational view, with The inside of the top wall 25 is preferably parts of the tone arm and parts of its supportformed with'a pair of longitudinally extending ing column in cross section taken on the plane flanges or ribs ll, 42 (Fig. 2) spaced suiliciently of the line 3-3, looking in the direction of the toform "a groove which will frictionally retain arrows: the conductors 43, 44 leading from. the reproat one end and having a body provided with an aperture for receiving a screw bolt 48, which passes through the aperture and is threaded into a lug that is integral with the tone arm.

The other end of each connectonshown at 49, may be of substantially T shape so that its oppositely projecting flanges may be bent about the wire of the insulated conductors 43 or 44 to which they are soldered,

The tone arm may have another integral inwardlyprojecting cylindrical lug 58 provided with a threaded aperture. Thus the conductors for connecting, the pickup in circuit, will pass tone arm is preferably provided with an inward-' ly projecting cylindrical wall 56, forming a tapered cylindrical socket 51 for receiving a metal body 58 preferably of lead or similar material. having a predetermined amount of inertia.

The lead body 58 is of substantially the same size as the socket 51, and is secured in place by driving it into the socket and spreading it slightly by impact with a tool. It is retained by friction.

The

ribs

53, 54 Previously mentioned are located at the supported end of the tone arm, and they provide the walls 28 and 21 with suflicient body so that bearing

apertures

53, 68 may be of greater length: At its free end the tone arm is preferably provided with a handle 6|, and this handle may take'the form of a cast metal member, having a supporting portion 62 and a finger piece 63.

The supporting portion comprises a body which is formed on its opposite sides with the parallel grooves 64,65 of substantially rectangular cross section. These grooves are wide enough to reducer to the connectors 45, 48. These connectors comprise strips of metal having a head 41 formed ed insulating material, such as a phenolic condensation compound, or some other form of molding powder, such as that called Bakelite.

All of the parts of the tone arm so far described, except the conductors and connectors, handle and weight, are of one integral piece, so that they may be manufactured economically and require no labor in assembly.

Therefore, the relatively light tone arm is provided with the inertia mass previously described. and indicated at 58, which has suflicient inertia so that the tone arm has the proper inertia characteristics. This mass also gives the tone arm sufficient weight at its free'end and concentrates the weight at the desired point, so that the needle will track properly in the record groove.

The present tone arm may be equipped with any desirable kind of reproducer or cutter. In the embodiment illustrated, the reproducer 88 is of the crystal type.

Referring to Figs. 3 and 4, the rear end of the tone arm is supported upon the column 5I, which comprises a tubular member having a through bore I38, having its upper end formed with a relatively narrow thrust surface. This narrow thrust surface is provided by making the end portion of the bore I38 frusto-conical and by providing 'a taper I at the upper outer surface of the cylindrical column 5|.

At its lower end this column has a reduced threaded portion I42, and there'is an annular shoulder I43, which engages a stamped sheet ceive the end wall '33 between the walls of the grooves, and the end wall is preferably provided with an upwardly extending slot 66 open' at the bottom so that the supporting portion 62 of the is equal to the depth of the body portion 62 at this point. The slot 66 is tapered and rounded at the top, and it receives the body portion 62 with a frictional fit of suflicient tightness so that the handle is retained by the tone arm.

l he finger portion 63 extends longitudinally outward from the body portion 62, as shown in Fig. 2, and has its lower part provided with a concave surface 61 for engagement with a finger. Its upper side may have a similar curvature.

In addition to serving as a support for the handle, the groove 66 also provides access to the needle-clamping screw 88 (Fig. 2), which is preferably made of the type having a threaded shank and a head with a cruciform socket that requires a special type of tool which the ordinary types of light metals, such as aluminum, or aluminum alloys; but is preferably made 'of a moldmetal collar I44. The collar I44 has a centrally located bore I45 for passing the reduced threaded portion I42, and it comprises a flange which extends downwardly and radially so that its lower and outer edge I 46 is adapted to rest on the phonograph table 28 Provision is made for securing this column 5I to the table 28 by providing the table 28 with a bore I41 for passing the reduced portion I42. A spring washer I48 and nut I49 are threaded on the lower end I42 of the column 5| to clamp the table 28 between collar I44 and nut I49.

The cylindrical bore I38 in the column 5| rotatably supports a tubular metal member I 58, the upper end of which is expanded into tight frictional engagement in a bore I5I in a metal bracket I52. The bracket I52 has a horizontal flange portion I53 with an aperture having a tight fit with the upper end of the tube I58, andthe flange I53 serves as a thrust bearing for the upper end of the tube I58 against the thrust bearing surface I39.

A very light spring washer of the wavy type is preferably interposedbetween flange I53 and thrust bearing surface I39 to prevent any'rattling. The lower end of the tube I58 is provided with a half cylindrical groove I54 extending completely aroun the tube and adapted to receive around spring wire I55, which is bent to substantially circular form, and which exerts a clamping action that retains it in the groove I54.

The spring wire I55 projects beyond the outer surface of the tube I58, and engages the end I55 of the column 5| as a thrust bearing, to keep the tube I58 in the column.

The bracket I52, as well as the tube I58, may belocated in the bore, and which has flanges I60, I6I on both sides of the bracket I52. The inner cylindrical portion of the grommet also insulates the body of a rivet I62 fromthe bracket, and this rivet is provided on the left side (Fig. 4) of the bracket I52 with a metal washer I63. The rivet I62 carries a U-shaped spring trunnion supporting member I64. Rivet I62 passes through the grommet I59 and through an aperture in the spring I64 in such manner that the spring I64 is tightly secured to the bracket I52; but there is no metal-to-metal contact between the bracket I52 and the spring I64.

The spring I64 comprises a strip of spring steel bent to substantially U shape and having its yoke I65 provided with theaperture for receiving the rivet I62. I

The two legs I66, I61 of this spring extend in the same general direction, but may diverge slightly, as shown in Fig. 4; and at their ends they are provided with apertures for receiving the riveted studs I68, which are similar in shape, but/ oppositely disposed.

Each stud I68 has an annular shoulder I69, which engages one side of the spring I61 and has a riveted portion on the other side of the spring. The main body of each stud is enlarged, and it is provided with a trusto-conical portion Ill and a reduced cylindrical portion I12.

This reduced cylindrical portion I12 fits in the bearing apertures 69 and 60 of the tone arm, while the irusto-conical portion I1I bears against the end portion of the apertures 59 and 60, and under the resilient compression of the spring arms I66, I61, any .wear which occurs in the bearing is taken up and rattling is positively prevented.

The tone arm is thus pivotally supported on the post 5| at an axis, which is disposed very close to the rear wall 29, and the flange I61 is of suflicient length so that as the tone arm pivots upward the rear wall 29 may pivot down into the space which appears between the tone arm in Fig. 12 and the flange I 63.

The characteristics of the tone arm and reproducer are greatly improved over the devices of the prior art. There is less needle wear due to the lightness of the tone arm. and the inertia characteristics of the tone arm may be adjusted to any desired value.

By locating the handle 62 and the weight 66 I near the free end of the tone arm. its mass is concentrated near the crystal pickup unit and made most eflective, and the tone arm may be made much lighter than if the same mass were distributed throughout the full length of the tone arm. I

The present tone arm may be manufactured at a very low cost because of the reduction in the number or its parts, and it may be assembled I more quickly than the devices or the prior art in which the reproducer is a separate unit before it is-placed in the tone arm.

The present tone arm support is. adapted to prevent the transmission of undesirable vibrations to the column and to the support or box of the phonograph, where they would be amplified, and would cause distortion. 7 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 claim.

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

In a tone arm the combination of a support with a column carried by said support, a tubular shaft rotatably mounted in said column, said tu bular shaft carrying a laterally and upwardly its legs, said bearing members each. being pro-,

vided with a cylindrical portion for receptionin' said apertures and with a conical portionfor taking up wear in said apertures, said U-shaped spring having an aperture in its yoke, a metal rivet having a headed end engaging one inside of said yoke, and said rivet passing through said aperture, said rivet having its body surrounded by a resilient elastic covering provided with flange portions located on each side of said upwardly extending portion of saidbracket, and said rivet having its opposite end provided with a thrust member and riveted over, whereby the spring is secured to said (bracket without metallic contact between: the bracket and spring, said upwardly extending portion of said bracket extending into said tone arm and spacing said tone arm from said tubular shaft, and said horizontally extending apertures being located immediately adjacent a rear wall of said tone arm, whereby the rear wall may be pivoted into a position between said U- shaped spring member and said column when the tone arm is tilted up past the vertical position.

. RQY DALLY.