US2145389A

US2145389A - Pick-up

Info

Publication number: US2145389A
Application number: US102303A
Authority: US
Inventors: Dally Roy
Original assignee: Webster Electric Co Inc
Current assignee: Webster Electric Co Inc
Priority date: 1936-09-24
Filing date: 1936-09-24
Publication date: 1939-01-31
Anticipated expiration: 1956-01-31

Description

Jan. 3l, 193., R @ALLY M5389 P10K-UP Filed sept. 24, 1936 @Um mi im@ Patented Jan. 31, 1939 UNHTED STTES PATENT OFFICE PICK-UP of Wisconsin Application September 24, 1936,-.Serial No. 102,303

'7 Claims.

The present invention relates to pick-ups, and is particularly concerned with pick-ups of the crystal type.

One of the objects of the invention 1s the provision of an improved crystal pick-up in which the crystals are adapted to be substantially hermetically sealed to prevent the crystals from absorbing moisture.

Another object of the invention is the provision of an improved crystal pick-up in which the crystals are subjected to a twisting action or a torque as distinguished from a bending action.

Another object of the invention is the provision of an improved crystal pick-up provided with an improved mode of securing the crystal elements in place and improved means for eecting an adjustment of the voltage output.

Another object is the provision of an improved crystal pick-up which is sturdy, eicient, capable of being used for a long time without deterioration, and capable of being manufactured at a low cost.

Another object of the invention is the provision of an improved pick-up arm of the sheet metal type in which the undesirable vibrations have been ydamped out and eliminated so as to prevent the eiects of resonance occurring in the arm.

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

Referring to the single sheet of drawings,

Fig. 1 is a top plan View of a fragment of a phonograph equipped with a pick-up and tone arm constructed according to the invention.;

Fig. 2 is a side elevational View of the tone arm and pickup;

Fig. 3 is a side elevational view of the pick-up unit;

Fig. 4 is a side elevational view of parts of the pick-up unit, with one of the covers or clamping members removed, showing the fastening members in section;

Fig. 5 is an elevational view of the inside wall of one of the clamping members, which also forms the pick-up housing;

Fig. 6 is a vertical sectional view through the pick-up unit, taken on the plane of the line 6-6 of Fig. 4;

Fig. 7 is a horizontal sectional View through the pick-up unit, taken on the plane of the line 'l-'I of Fig. 4, looking in the direction of the arrows;

Fig. 8 is a vertical sectional view through the pick-.up unit, taken'on the plane of the line 8-8 of Fig. 2,;showingthe 1detailsof support of the needle;

Fig. 9 isa fragmentarysectional View, similar to the right end of Fig. 7, showing the details of connection for a series` connection of the crystal elements.

Fig. 10 is a vertical sectional View. through the trunnion for the tone arm, taken on the plane of the line lll- Hl of. Fig. 2, looking in the direction of the arrows..

Fig. 11 is atransverse sectional view through the tone arm, taken on the axis Vof the sleeve and screw `92, 93.

Referring to Figs1-.and 2, I0 indicates in its entirety the phonograph equipped with the usual turntablell, bearinga record l2and having a tone arm I3. The tone arm I3 is rotatably and pivotally supportedvu-pon a base member I4, which Ina-y consistv of a substantially cup-shaped sheetl metal stamping having an upper cup eX- tension I5.

The upper `cup extension is provided with a centrally located bore I6 adapted to rotatably receive a tubular shaft I'I` having an upper frustoconicalportion I.8',-fwhicl'lis extended into. a cross piece` t9 and rivetedtherein. The cross piece I9: preferably has an integral, upwardly curved stop arm 2U, which is adapted to engage the inside of the tone :arm I3 and support the tone arm with its needle elevated when the tone arm is not resting on the record I2.

The base I4 maybe secured tothe top of the phonograph by means of screws or other convenient fastening means, and ritis conveniently provided with a groove 2.I in its side wall for passage of .

theelectric conductors

22, 23 provided with the pick-up. The base I4 supports the frusto-conical portion.: If8 ofV the shaft I'I for rotation on a vertical axis, thereby adapting the tone arm to move to different positions radially with respect to the record I2.

The cross piece I9 is preferably provided in its ends with the stamped, frusto-conical sockets 24, eachA of which is adapted to receive the conical end of a screw bolt 25 held in place by a lock nut 26. The cross piece I9 comprises a resilient bronze leaf which is sprung sufficiently to place a slight spring pressure on the conical bearo ings, the lfacesof which are kept constantly engaged by the leaf.r This eliminates entirely any tendency toward chattering in the bearing when vibration is applied to the tone arm, and wear is automatically compensated for by the tendency of the cross piece I9 to take up any wear.

Screw bolts 25 are threaded into the side Walls 21, 2B of the tone arm I3 and are so adjusted that they engage in the frusto-conical sockets 24 of the cross piece I9, thus rotatably supporting the tone arm I3 on the cross piece I9. This permits the tone arm to be lifted from the record so as to remove the needle from the record, and at the beginning or end of the playing of a piece. It also permits the tone arm to follow the irregularities in the record so that the needle may rise or fall as required when the record rotates.

The tone arm I3 preferably comprises a stamped sheet metal member which may be provided with side walls 21, 2B and an end wall 29, the opposite end being open at 30 until closed by the insertion of the pick-up unit. The tone arm I3 is pivotally supported on the cross piece I9 by the screws 25 at a point which is closer to the end 29 than the end 30.

The end portion 29 of the tone arm is suitablir enlarged to provide space for a frequency adjusting unit 3|. This unit 3I comprises an electrical lter unit having one or more resistance coils in connection with a condenser intended to be used to adjust the frequency response of the pick-up to any desired degree.

The tone arm is preferably used with an additional amount of resistance required to make the shunt resistance load between pick-up and tube grid circuit not less than 500,000 ohms.

The

side walls

21, 28 and end walls 29 are joined by a top wall 32, and thereby form an arm of substantially U-shaped cross-section, except for certain ornamental configurations made for the purpose of improving its appearance.

The

side walls

21, 28 are provided with apertures 32, which are aligned with each other and which are adapted to receive the threaded sleeves 33 and the screw bolts 34 which pass through these walls, through a metal stirrup 35, and through the pick-up unit 36, to secure the pickup unit to the tone arm. The metal stirrup 35 comprises a sheet metal member having two

legs

31, 38 which embrace the sides of the pick-up unit 36, and a Wider yoke 39, which substantially covers the end of the pick-up unit, and which is provided with an aperture for passing the needle securing screw 40.

The pick-up unit 36 preferably has its housing made of two identical halves 4l, 42 of molded insulating material, such as Bakelite or other phenolic condensation compound, or die cast metals. The half housing members are provided with the fiat or plane side walls 43, top 44, and back 45, which are substantially rectangular in shape, but it is provided at the needle end with a downward extension 46 adapted to house the needle chuck 41 and the screw 40.

While the halves of the housing are identical in shape, they differ in the fact that the half portion 4I preferably has embedded in its end 48 a pair of longitudinally projecting connector strips 49. These, connector strips comprise strips of metal embedded in the Bakelite and having at their outer ends threaded bores for receiving the screw bolts 50 which clamp the

conductors

22, 23 to the connector strips 49,

The connector strips 49 project into an element chamber 5I, where they have extensions that are soldered to leads 52 suitably connected to the foil which is associated with the crystal elements. When the crystal elements are connected in parallel, as exemplied in Fig. '1, one lead 52 may be brought out from the central foil 53 or from any number of alternate, centrally located foils, and the other lead 54 may be connected to the two outer foils 55, or to the alternate series of foils, if a larger number of crystal elements and foils are used. When the elements are to be connected in series, one lead 52 is connected to the outermost of the foils 55, and the other lead 54 is connected to the outermost of the foils 56 associated with the crystal elements.

The

lcrystal elements

51, 58 comprise flat plates of suitable crystals, such as Rochelle salts, and in the present case the strips are preferably trapezoidal in form, as shown in Fig. 4. The

crystal elements

51, 58 are separated by the metal foil 53, which serves to collect any electric charge generated, from all parts of the surface of the crystals, and on each of the outer surfaces of the

crystal elements

51, 58 there are the foil coverings 55 and 56. The foils and crystal elements are cemented together by suitable cement, such as, for example, melted Rochelle salts, thereby forming a unit which may be installed in the pick-up as such.

The housing halves 4I, 42 are provided with the substantially rectangular depressions 5I, forming the chamber 5I when the two halves are placed together as shown in Fig. 6 or 8. Each of the halves has projecting into the chamber a plurality of

lugs

59, 60, 6I and adapted to serve 9 as clamping jaws for engaging the sides of the crystal unit to clamp it in position in the pick-up. These lugs 59-6I may consist of small blocks of rubber cemented to the interior walls of the chamber 5I and thick enough so that the resilient rubber blocks 59-6I are suitably compressed to clamp the crystal unit in place when the halves 4I, 42 are secured together as shown in Fig. 6.

Any number of such resilient rubber blocks may be used, two of them being preferably located at the extreme right ends of the broadest part of the crystal element so as to secure that end of the element against rotation.

,The additional rubber block 6I disposed near the middle of the element also serves to clamp it, but, being made of rubber, does not prevent transmission of torque from one endA of the element to the other. The left ends of the housing parts 4I, 42 are each formed with half of the sockets necessary to house the armature 41.

The needle chuck 41 comprises a metal member which may be made of die cast metal having a pair of

cylindrical trunnions

62, 63, which are aligned with each other and are carried by a body having a downwardly and outwardly extending needle supporting portion 63. The needle supporting portion 63 may be substantially rectangular or round in section, and is provided at its lower end with an axially extending bore 64 adapted to receive the needle 65.

The trunnion 62 may have a threaded bore 66 communicating with the needle bore 64 and threaded to receive the securing screw 40 which engages the needle and clamps it in the bore 63. Each of the

trunnions

62, 63 is provided with a resilient rubber bearing sleeve 68 which is held on the trunnion by its own tension, being a closed rubber band tensioned about the cylindrical surface. 'Ihe rubber bearing members 68 are adapted to be received in the hemi-cylindrical grooves 69 which are formed in the housing halves 4I, 42, and which provide bores for receiving the rubber sleeves 68 when the housing halves are secured together.

The sockets 10 in each half 4I, 42`surrounding the armature body 41 provide a clearance around this body so that it may rotate on the trunnions E2, 63, and each side of the armature is preferably engaged above and below the trunnions by resilient rubber blocks 1l to 14. These rubber blocks may be slidably received in the threaded bores 15 and engaged by the threaded members 16 so that they can be driven into resilient engagement with the armature 41 to regulate the resilient pressure under which this member moves.

The housing may be sealed against moisture by an additional resilient rubber band or ring 16 which surrounds the body 41 in the bore 11 and elects a water-tight and hermetic seal at this point. the rubber sleeve 18 is to automatically center the needle chuck 63 in the cavity in such manner that it cannot strike the housing during normal operation. The rubber sleeve 68 seals the housing at the trunnion 62, and suitable cement or a gasket may be applied, if desired, between the opposing

surfaces

18, 19 of the halves 4|, 42 of the housing.

The trunnion 63 has a flat attaching flange 80 projecting axially therefrom and provided with a threaded bore 8l for receiving a screw bolt 82. A clamping plate 83 has a bore 84 for receiving the screw bolt B2, and its plate is driven Vinto clamping relation with the crystal element by means of screw bolt 82. Rubber sheets 85, 86 are interposed between the flange 80 and the crystal element and between the flange 83 and the crystal element, insulating the foil from the needle and providing a resilient gripping action for the clamping members 80, 83. The left and smaller end of the crystal element is, therefore, secured to rotate with the

trunnions

62, 63 of the needle chuck.

The adjusting clamp, comprising the shoulder 88, screw 82, clamp 83, and rubber sections 84 and 85, comprise a means for varying the voltage output of the pick-up without disturbing the frequency response. The motion of the needle point and needle chuck up to the clamp is constant, depending upon the frequency being reproduced. The torque developed by the clamp as a result of this motion also depends upon the frequencies being reproduced, but when applied through rubber to the crystal elements the torque applied to the crystal element may be varied over a large degree by varying the pressure applied to the clamp and rubber by the screw 82. The greater the pressure applied, the greater the voltage output will be, due to the added stress induced in the crystal element, and one of the most important features of the invention is the arrangement whereby the voltage output may be adjusted without disturbing the frequency response.

The flanges lill-83 may be made trapezoidal in shape, increasing in size toward the right end, as shown in Fig. 4, to clamp across the full width of that end of the .crystal element. The two halves 4l, 42 of the housing are preferably secured together by tubular rivets 80, which are adapted to pass the securing screws 33, 34 which extend through the

side walls

21, 28 of the tone arm and through the pick-up to secure it in place.

The present pickup is adapted to be used with records of the type having a groove which causes the needle S5 to move laterally in response to the contour of the groove to reproduce sound. When One of the most important purposes of the needle 65 vibrates in a lateral direction about the axis of the trunnions62, '63, the needle chuck has a rotative movement which tends to twist the crystal element, since the opposite end of the crystal element is held in fixed position. The torque produced in the crystal element produces a condition of strain which generates an electromotive force, the amount ofthe electromotive force depending upon the amount of torque, which depends upon the amplitude of vibration of the needle at any time. The present pick-up is, therefore, adapted to produce an electromotive force which, when amplified, reproduces sound recorded upon the record, and it may be used with any suitable amplifying circuit, such as that of a radio receiver.

Referring to Fig. 11, this is a cross-section, taken through a damping block 9D, which is shown in dotted lines in Fig. 1. The channeled arm I3 is preferably provided with a lead block 90, which is a substantial t between the anges of the channel. This block has an aperture Sl for passing the screw sleeve 92 and screw bolt 93, the heads of these members engaging the outside of the flanges of the tone arm and drawing them into close engagement with the lead block 90.

The block may have a groove at the top for holding conductors in proper place. The purpose of this lead block or plug is to damp out the resonance which occurs in the arm, and it is found that the most satisfactory material is lead, due to its very inert nature. Materials other than lead have not proved satisfactory for the reason that they do not have a satisfactory damping action. The free edges of the channeled Itone arm are tightly clamped in engagement with the lead plug by means of making the aperture 9| an oversized hole.

The pick-up is adapted to be used for a long period of time without deterioration because of its improved structure and because of the crystal being sealed against access to moisture, not only by the vcoverings of foil, but by the sealing of the housing with the rubber bearings and gaskets. It is found that a pick-up operating upon the torque principle reproduces sounds faithfully and efliciently, and that the present pick-up may be constructed at a low cost which places it within the means of a large number of purchasers.

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, is:

1. In a crystal pick-up, the combination of a housing comprising a pair of clamping housing members having a chamber therein for receiving the crystal element, said housing having resilient blocks interposed between one end of the crystal element and said housing and effecting a clamping action, a needle supporting member rotatably mounted in said housing and secured to the other end of said crystal element whereby vibration of the needle is adapted to produce torque strains in the crystal element, said needle supporting element having trunnions extending substantially axially of the length of the crystal element, and resilient means engaging movable parts of said needle supporting member and engaged by threaded members for adjusting the resilient characteristics of said pick-up.

2. In a crystal pickup.the combination of a supporting housing withA a crystal member, said housing comprising a pair of complementary housing members formed with registering recesses to provide a crystal chamber, said crystal member being xedly supported at one part and being connected to a needle supporting member at its other part, said needle supporting member being mounted for rotative movement whereby torque is induced in the crystal member to generate electromotive force responsive to the movements of the needle, said housing being provided with resilient cylindrical bushings surrounding all projecting parts of said pick-up and engaging in cylindrical bearings in said housing to seal the pick-up against ingress of moisture.

3. In a crystal pick-up the combination of a housing comprising a pair of complementary members formed with registering recesses adapted to form a crystal chamber and chuck bearings with a crystal in said crystal chamber, and means carried by said housing for engaging said crystal at the point remote from the chuck, a chuck rotatably mounted in said chuck bearings and secured to said crystal, said chuck having a downwardly extending needle supporting portion carried in an.additional recess in said housing, and a resilient rubber bushing surrounding said needle supporting portion to prevent ingress of moisture into the housing at that point.

4. In a crystal pick-up, the combination of a housing comprising a pair of complementary members formed with registering recesses adapted to form a crystal chamber and cylindrical chuck bearings with a crystal in said crystal member, and means carried by said housing for engaging said crystal at a point remote from the chuck, a chuck rotatably mounted in said chuck bearings and secured to said crystal, said chuck having a downwardly extending needle supporting portion carried in an additional recess in said housing, and a resilient cylindrical rubber bushing surrounding said needle supporting-portion and engaging said housing and projecting parts to prevent ingress of moisture into the housing at that point, said chuck having resilient rubber bushings surrounding trunnions of said chuck in said chuck bearings.

5. In a crystal pick-up, the combination of a supporting housing with a crystal member, said crystal being iixedly supported at one end and being connected to a needle supporting member at its opposite end, said needle supporting member being mounted for rotative movement whereby torque is induced in the crystal member to generate electromotive force responsive to the movements of the needle, and said housing being provided with resilient bushings surrounding the projecting parts of said pick-up to seal the pickup against ingress of moisture, and resilient bodies engaging said needle supporting member on its opposite sides adjacent the needle supporting portion for regulating the resilient characteristics of the pick-up.

6. In a crystal pick-up, the combination of a supporting housing with a crystal member, said crystal being fixedly supported at one end and being connected to a needle supporting member at its opposite end, said needle supporting member being mounted for rotative movement whereby torque is induced in the crystal member to generate electromotive force responsive to the movements of the needle, and said housing being provided with resilient bushings surrounding the projecting parts of said pick-up to seal the pickup against ingress of moisture, and resilient bodies engaging said needle supporting member on its opposite sides adjacent the needle supporting portion for regulating the characteristics of the pick-up, and threaded members for engaging said latter blocks to effect adjustment of the pressure on said latter blocks.

'7. In a crystal pick-up, the combination of a supporting housing with a crystal member, said crystal member being xedly supported at one end and being connected to a needle supporting member at its other end, said needle supporting member being mounted for rotative movement whereby torque is induced in the crystal member to generate electromotive force responsive to the movements of the needle, said needle supporting member having a clamping arrangement for engaging the end of said crystal, and a resilient pad included between said crystal and said clamping arrangement whereby the crystal may be resiliently clamped, said clamping arrangement having threaded means for regulating the characteristics of the connection between the crystal and the needle supporting member.

1 ROY DALLY.