US1844623A - Pick-up arm - Google Patents

Description

Feb. '9, 1932/ A. YEIDER PICK-UP ARM v Filed July 28, 1928 2 Sheets-Sheet 1 ATTORNEY.

WztnessQ Mai- Patented Feb. '9, 1932 PATEN'T oer-Ice H.ARRY A. YEIDER, OF GRAND RAPIDS, -MICHIGAN, ASSIGNOR TO AUTOMATIC MUSICAL INSTRUMENT COMPANY, OF GRAND RAPIDS, MICHIGAN, A CORPORATION OF DELA- 'WARE rrcx ur ARM Application filed July 28, 1928. Serial No. 295,895.

This invention relates to pick-up arms for phonographs and the like.

The main objects of this invention are to provide improved means for transmitting mechanical vibrations to a distant point without distortion; to provide an improved pickup arm for phonographs which use electrical amplifying and speaking means whiclrwill produce a truer and better quality reproduction without the use of a condenser in the electric circuit than has heretofore been obtained with the use of such condenser; to provide improved means for dampening the vibrations of a stylus bar so that it will transmit without distortion, vibrations imparted to it; and, to provide an improved method of constructing such a pick-up arm.

d An illustrative embodiment of this invention is shown in the accompanying drawings, in which I Fig. 1 is a vertical longitudinal sectional view of the improved pick-up arm and mounting therefor, a portion of the arm being shown in elevation.

Fig. 2 is a top planview partly in horizontal section of the same.

Fig. 3 is a view in elevation of the permanent magnet and solenoid coil at the rear'end of the pick-up arm with the arm shown in section.

Fig. 4 is a sectional view taken 44 of Fig. 1; I

Fig.5 is a thin sectional view taken on the line 55 of Fig. 1.

Fig. 6 is an enlargedview of the stylus mounting taken in longitudinal medial secon the line tion.

- Heretofore in the construction of pick-up arms of the class described it has been customary to employ a condenser in the electrical circuit which amplifies the electrical pulsations produced by the mechanical vibrations of the phonograph record, for the purpose of eliminating or minimizing the needle scratch sounds and the like.

I have discovered, however, that what has heretofore been considered: needle scratch which takes place in the stylus bar as it transmits these mechanical vibrations t0 the electrical unit. This distortion is caused by inde pendent vibrations set up in the stylus bar and in the housingtube within which the stylus bar is mounted. H

This objectionabledistortion has been eliminated in the present construction by mounting the stylus "bar in the housing without having metallic contact therewith and then filling the space between the bar and housing with a congealable fluid which is soft and pliable when it congeals.

The dampening material used for filling the'housing may be a mixture of glue and glycerine which has a melting point well,

above 100 F. Any substance however which 1s pliable at normal weather temperatures would be equally suitable for this purpose, although the best results are obtained from a material which has very little, if any,

shrinkage. If substantial shrinkage occurs when the material cools and congeals, it

draws away from the housing and from the stylus bar and the best results are not obtained.

In the construction shown in the drawings, a thin metal housing tube 1 has its opposite ends closed by bearings 2 and 3 which are in the form of discs slidably fitting in the ends of the tube and secured therein by screws 4 and 5 respectively. The inner faces of the bearings 2 and 3 have axially-disposed sockets 6 and 7 concentrically located ther'eiv which are adapted to receive soft rubber tub 1- lar bushings 8 and 9 respectively.

A stylus bar 10 in the form of a brass rod is provided with reduced ends 11 and 12 which snugly fit within the bushings 8 and 9 so as to support the bar concentrically within the housing tube l'in spaced relation thereto and without having any metallic -contact therewith. Closely adjacent the end 11, the

posed passageway adapted to receive the upper end of a stylus mounting 13, sald mounting being rigidly secured in the bar by bar 10 is provided with a transversely-dissoldering the two pieces together. The lower end of the mounting 13 extends out through an. aperture 14 in the tube 1, said aperture being of considerably larger size than the size end thereof projecting up into the larger bore 15. A collar or head 17 is integrally formed on the plunger 16 and is adapted to have axial sliding fit in the bore 15. The outer end of the bore is threaded to receive a closure screw 18. Means are provided for normally urging the plunger 16 outwardly or downwardly so as to eject a stylus 19 and comprises acompression spring 20 within the bore 15 which bears between the inner end of the screw 18 and the head or collar 17.

The opposite end of the stylus bar 10 is drilled'and threaded at right angles to the axis thereof to threadably receive a stud 21 which hasa reduced shank 22 thereon The stud 21 projects out through an aperture 21A formed in the tube 1 which is also of considerably larger size than the stud so as .to provide ample clearance therearound.

An armature 23 is rigidly secured to the reduced shank 22 by a screw 24 so as to be readilyadjustable and removable. The armature 23forms a core of a coil 25 which is supported by pole pieces 26 and 27 of a permanent magnet 28 which is horseshoe in shape and which embraces the housing tube 1 near the rear end thereof. The shank portion 22 of stud 21 is reduced (i. e. is of less di.ameter than the upper portion of said :ill

stud) in order to be received into the hollow upper end of the armature 23 which is of no greater diameter than said upper portion.

The entire rear end of the housing tube 1 together with the permanent magnet 28. coil 25 and its assembly is housed within a bell-shaped housing 29. The housing 29 is pivoted on diametrically-disposed studs 30 and 31 carried by an upwardly-facing yoke- 32 which is supported on a shank 33 pivotally mounted on a vertical axis -in a supporting housing 34 so that the pick-up arm will have horizontal swinging movement and limited movement in a vertical plane.

The annular space between the stylus bar It) and the tubular housing 1 is filled with a vlbration dampening material 35 which supports. and contacts with. the bar 10 alon r its entire length and completely fills the tu e 1.

This vibration dampening material. as herelnbefore stated. may be a mixture of glue and glycerine which h a meltin point above the normal weather temperatures and which has very little shrinkage when it cools and congeals. This vibration dampeningmaterial when in its congealed state is prefer-, ably of a soft or pliable or rubbery'nature so that the mechanical vibrations imparted to one end of the stylus bar 10 are transmitted without distortion to the opposite end thereof. In the assembly of this device, the soft rubber bushings 8 and 9 are placed in the sockets 6 and 7 respectively of the bearing discs 2 and 3 respectively. The aperture 14 at the front end of the tube 1 of an open ended slot and the stylus bar 10 with the stylus mounting 13 soldered rigidly therein is slipped into the tube 1 with the rear reduced end 12 in the bushing 9. The front disc hearing 2 is then telescoped into the end of the tube 1 with the reduced end 11 of the bar 10 entering into the bushing 8. The stud 21 is then threaded into the bar 10 through the aperture 21A. The vibration dampening material 35 in its heated and fluid form-is then poured into the tubular housing 1, completelyfilling the same and allowed to cool and congeal.

In the use of this pick-up arm. the stylus 19, by reason of its contact with the grooves in the record, transmits mechanical vibrations to the stylus bar 10 which carries these vibrations in true and undistorted manner to the other end thereof. thence through the stud 21 to the armature 23 which is secured thereto. v

In this action the stylus 19 travelling in the laterally undulating groove of the revolving record disk rocks the bar 10 slightly about its longitudinal axis, thus swinging the armature 23 relatively to the magnet 28 and pole pieces 26 and 27. In this manner true and undistorted mechanical vibrations are transmitted and converted into electrical pulsations without distortion and without the usual attendant scratching and objectionable noises heretofore encountered and which have beenattempted to be eliminated by the use of a condenser in the electrical output circuit.

Although but one specific embodiment of this invention has been herein shown and described. it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

Iclaim:

1. In a device of the class described. the

' combination of a supporting housing. a stylus bar within said housing, a stylus mounting I on one end of said bar, an armature mtively connected to the other end of sai bar and a vibration dampening material contacting with said bar. and easing intermediately the ends of saidhar.

" 3. In a deviceof the class described, the

combination of a supporting housing,-a stylus bar within said housing, a stylus mounting on one end of said bar, an armature operatively connected to the other end of said bar and soft pliable material surrounding said bar and supporting the same within said housing without contacting any metallic part of the device.

4. In a device of the class described, the combination of a supporting housing, a stylus bar within said housing, a stylus mounting on one end of said bar an armature operatively connected to the other end of said bar and. a

vibration: dampening material surrounding said bar and supportmg the same within said housing without contacting any metallic part of the device.

5. In a device of the class described, the

combination of a tubular housing, a bearing in each end of said housing, each of'said bearings having a socket therein, a soft rubber bushing in each of said sockets, a stylus bar supported in said bushings in spaced relation to said housing, the space'between said bar and housing being filled with vibration damp- .ening material, a stylus mounting on one end of said bar extending out through an aperture in said housing spacedly therefrom and an armature operatively connected to the other end of said 'bar and extending out through another aperture in said housing spacedly therefrom.

6. A pickup arm for phonographs comprising: a housing mounted for horizontal and vertical arcuate movements and having flexible end members; a stylus bar carried by said zontal and vertical arcuate movements and having flexible end members; a stylus bar inside the housing, spaced therefrom, carried by said niembers'rockably about its longitudimil axis and carrying at one end a laterally extendingstylus mounting and at its other end a laterally extending armature; soft pliable material within the housing and spacing the same from said bar, stylus mounting and armature; and electrical impulse-transmitting means cooperating with the armature.

In testimon .whereof I have hereunto set my hand at rand Rapids, Michigan, this 26th day of J 111y,1928.

HARRY A. YEIDER.

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