US1721362A - Phonograph arm - Google Patents

Description

2 Sheets-Sheet 1 A1TORNEY July 16, 1929.

July 16, 1929. R. s. wElR PHONOGRAPH ARM Filed June 5, 1928 l2 Sheets-Sheet 2 INVENTQR 75.5. Wezr WITNESSES ATroRNEY atented July 15, 192

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BORT S. WEIR, OF GREENFELD, IMISSUBI.' I

PHONO GRAPH if i Application led June 5, 1928. Serial No. 283,068.

rIhis invention concerns a phonograph, and has particular reference to the construction and assembly of the tone arm and the connection of the sound box and needle thereto.

It is the object of the inventionto suspend a sound box and needle assembly withini a tone arm in such manner that the maximum output of the needle vibrations will be transmitted intovsound waves and incur" minimum loss by absorption in the mechanical parts' of the apparatus.

It is also an object to suspend a sound box and needle unit so freely that they may be said to oat and have most efficient and free frictionless production of vibration.

A further object is to mount the tone arm so that little friction is involved in its gradual turning .as the needle moves over the record, and in fact, it is part of the inventionto provide means whereby the tone arm assists the needle'in its travel in the sound grooves.

As a further object, I intend to so cushion or dam-p the parts and their supports, that no vibrations pass except direct from the needle tothe dlaphragm.' f

To Ithis end, the invention comprises a tone arm mounted on a swivel joint which 3o is provided with means tobias the arm laterally in a given direction so as to assist the needle in its groove travel. The joint' is provided with a flexibly connected throat held resiliently thereagainst tocontinue the sound passage, but permit Vfree movement between the parts.

The sound box and needle lsupport are mounted on a pivot which is cushioned against vertical and lateral vibrations so that none or the vibratory energy of the needle is lost. Furthermore, the sound box and needle unit is balanced on'each side of the pivots by means such as weights so that it is not positively or rigidly connected to 45. the tone arm, and consequently floats therein in a very sensitively dynamic state, whereby a maximun of sound is produced without loss of vibrations through inert parts of theA mechanism:

A preferred embodiment is shown in the drawings, of whiche- Fig 1 is a vertical longitudinal section through the tone arm and sound box as- Sembly,

c D of the lnventlon4 Fig. 2 is a Elan view thereof, showing certaln casings roken away.

Fig. 3 is an enlarged plan view of the sound box mounted with the enclosing casing cut away. l

Fig. 4 is a section on the line 4--4 of Fig. 3.

Fig. 5 is a section on the line 5--5 Vof Fig. 2.

Fig. 6 is a plan` view partly in section of a modified form of pivot bearing for the sound box and its associated mechanismf rThe preferred form as shown in the drawings, is mounted on a platform y10 on lwhich a turntable 11 is mounted to receive a record 12. A throat 13 projects through the platform 10 and connects loosely with the end '14 of a horn mechanism (not shown). This throat is .held resilently against a ball shaped swivel joint member 15 by means of springs 16 and 17 fastened to an vupright plate 18 mounted on the platform 10. This late 18 has a curved socket 19 against whic the rear face of `the ballV swivel member 15 bears. A shaft 20A ex- -tends upwardly from the member 15 and is journalled 'in the plate 18 at the top. A cable 20 assthrough the plate 18 and is wrappe the plate 18, it passes over pulleys 21 and extends downwardly to support a weight plate 28. This plate has a lateral Aextension 29 at the top, from which depends a link 30 connected to a dam er plate 31 in the bottom of casing 32. Above the damper plate 31 within the casing 32 is disposed a mass of flexible material, vsuch as'packing 33.v

The casing 32 is supported at one end of va'weighted arm- `34 pivoted atA 35 on the tone arm. Over this mechanism extends a,

cover 36. Th weight of late 28 tends to hold..- the nee e rmly in te groove 0 11 the around the shaft 20A. Back of l plate 31 through the packing or cushion 33.

,Howeveig the vibrationsl of the needle by reason of the packing will not pass to the weighted arm 34.

' Within the tone arm 25, a sound box 37 is pivotally mounted. This soundbox has a diaphragm 38 to the under side of which the needle arm 27 is centrally connected. Intermediate its ends, this needle arm passes through a ball pivot member 39 which rests on a liexible cushion 40 disposed between it and the adjacent surface of the tone arm, This pivot member has laterally extending` arms 41 and 42 provided with ball shaped ends 43 and 44 resting in curved sockets 45 and 46 on the ends of arms 47 and 48 extending from the sound box. These sockets 45`and 46 in turn are received by curved sockets 49 and 50 on threaded stems 51 and 52 threaded into sliding plates 53 and 54 mounted on fixed plates 55 and 56 supported from the tone arm with layers of flexible packing 57 and 58 therebetween. The outer ends of the threaded stems 51 and 52 have curved balls 59 and 6() with which engage the ends 61 and 62 of arms 63 and 64 extending from a weighted plate 65 disposed beneath, but

. not inconta'ct with the sound box 37. 4On

the outer end of this, weighted arm 65 -is a casing 66 containing flexible packing 67 and a damper plate 68. This plate is connected bya link 69 to an arm 70 extending from the sound box.l

Mounted on top of the tone arm is la cover I 71 beneath which is a weighted arm'72 ter of the diaphragm 38 at the top, and thecord 78 connected to the'sound box 37.

In the modification shown in Fig. 6,V the needle arm 27 is supported on a conical ended pivot member 80 seated in adjustable bearings 81' and '82 disposed in a plate83 mounted on the tone arm. The oppositeend of this plate is providedwith extending shafts 84 and 85 having grooves such as 86 therein to receive' set lscrewssuch as 87 0n ring-shaped collars 88 formed on the ends respectively of arms 47, 48', 63 and 64 above mentioned. These arms 'can rotate around the shafts, but will not have any lateral movement with respect thereto.

This type of construction land assembly will permit a free vertical movement of the sound box, its diaphragm and the needle arm,

but any lateral movement therewith, will be prevented. Furthermore, by reason of the opposed weights connected to the sound box and needle arm unit on opposite sides of thel main pivot, the assembly is in a state of delicate dynamic balance to'be responsible in a'maximum degree to the vibrations set upy in the needle. By reason of 'the flexible cushion or packing disposed at the points above mentioned, these vibrations are not allowed to be transmitted to other parts of the mechanism, and consequently a maximum of volume is achieved and a pure tone results.

The effect of weight 72 is to pull up on the sound box, whereas the effect of weight 65 is to pull down on the sound `box.

weight of the sound box on one side ofthe pivot member 39 is balanced by the effect of the weight 34 and the plate 28 on the needle 26. Consequently, the sound box and the needle are delicately supported, the sound box vsubstantially floating with the tone arm.

I claim:

l. In a phonograph, a tonearm, a sound box pivotally supported therein out of contact therewith, a needle arm extending from the tone arm to contact with a record and connected to said sound box, andmeans for These weights are so balanced that very 'little stress is set up in the packing 67. Similarly, the

cushioning the support of said, sound box and needle arm against vertical and lateral vibrations.

2. In a phonograph, a tone arm, a sound box pivotally supported therein out of contacttherewith, a cushion for said pivot to nected to the sound box, a weighted element l connected to the needle arm, and cushioning means between said weightedelements, the sound box and the needle arm.

3. In a phonograph, a tone arm, a sound box pivotally supported therein out of.co n tact therewith, cushioning means for said pivot against vertical and lateral vibrations thereof, a weighted element connected to said sound box tending to exert an upward force thereon, a second weighted element connected to said sound 'box and tending to exert a downward force thereon, and cushioning means between the sound box and one of said 'weighted elements.

4. In a phonograph, a tone arm, a sound box pivotally supported therein out of contact therewith, cushioning vmeans for said pivot against vertical and lateral vibrations thereof, a weighted element connected to said sound box tending to exert an upward force thereon, a second weighted element connected to said sound box and tendingto exert a. downward force thereon, cushioning means between the sound box and one of said weighted elements, aneedle arm extending from the sound box in the opposite direction from the pivot, said needle arm connected to the sound box, a weighted element'associated with the needle arm, and cushioning means between the needle arm and said Weighted element. Y

5. In a phonograph, a tone arm, a sound box pivotally supportd therein out of contact therewith, .cushioning means for said pivot against vertical and lateral vibrations, a needle, arm connected to the sound box and extending from the tone arm in the opposite direct-ion from the pivot, and weighted ele- `box pivotally supported therein out vtact therewith, cushioning means ments connected to the sound box and the needle arm to maintain them in a state of sensitive dynamic balance.

6. In a phonograph, a tone arm, a sound of confor said i pivot against vertical and lateral vibrations,

a'needle arm connected to the sound boxand extending from the tone arm in the opposite direction from the pivot, weighted elements connected to the sound box and the needle arm to maintain them in a state of sensitive dynamic balance, and cushioning means disposed between said weighted elements, the

sound box and the needle arm. v

OBEBT S. WEIR.

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