Патент USA US2124296код для вставки
July 19, 193s. 2,124,296 _ E. c. GUEDQN TRANSDUCER Filed July 31. 1935 ` EG. 1. .n a A.. i, ' 22 , IN VEA/'ron Emile C. Guedon 2,124,296 Patented July 19, ‘1938 PATENT OFFICE UNITEDN STATES 2,124,296 TRANSDUGER to :Emile vC. Guedon, Audubon, N. J.,a assigner corporation Radio Corporation of America, ‘ of Ílela'ware Y Appncatión july 31, 1935, serial No. 34,016V 10i Claims. (c1. 17e-¿100.411 sidered in connection with the accompanying The present invention relatesto transducers drawing and its scope will be Vpointed ’out in the or translating devices for converting or translat appended claims. ing electrical signal currents into corresponding mechanical Vmovement of an armature member greatly enlarged scale of an electro-magnetic and for converting or translating mechanical movement of saidarmature member into corre sponding electrical currents. . More particularly, the invention relates to pickup device or transducer embodying the in vention, with a cover removed to expose the in I terior mechanism; transducersof the electromagnetic pickup type employed in phonographrecording and repro 10 ducing systems and comprising a vibratory ar mature adaptedto carry a stylus or needle, an electric pickup coil surrounding the armature and a permanent magnet associated with the 15 armature and the coil to provide exciting flux. The invention has for its primary object to provide an improved and simplified construction in a transducer device of the character referred *to> having operating elements which may be more 20 rapidly and easily assembled and adjusted in predetermined relation to each other and which may withstand more severe handling in shipment land'in servicing than has heretofore been possi l25 ble in like devices. _. , , It has been the practice heretofore in trans ducers of the electric pickup type to provide a pair of pole pieces for the permanent magnet having an air gap maintained constant by a non magnetic bridge piece connecting the pole pieces. 30 The magnet itself is usually removable from the pole pieces, being held thereon merely'by aspring tension or by magnetic attraction alone. Be cause of this arrangement the magnetic circuit wasoften momentarily broken when the magnet 35 was moved by vibration or by accident in servic~ ing the device, with the result that the magnetic field thereafter was greatly reduced in strength and required recharging of the magnet before efñcient operation could be obtained. 40 It is, therefore, a further objectof the pres ent invention to provide an improved magnet and pole piece construction in a transducer de vice of the electro-magnetic pickupI type, where~> in the air gap is maintained at a permanent 45 predetermined width-by the magnet itself ¿acting as a yoke, permanently welded to the pole piece. It is also a still further object of the invention to provide an arrangement of parts in a trans ducer device of the electro-magnetic pickup type 50 which renders such a device compact in construc~ vtion and highly efficient electrically in producing relatively high output potentials in response to normal vibratory movement of the armature. The invention will, however, be better under stood from the following description when con V In the drawing, Fig. 1 is a front view on a f Fig. 2 is a cross `sectional view of the device shown in Fig. 1 and on the same scale, taken on 0 line 2-2 vand with the cover in place; Fig. 3 is a bottom view of the device shown in Fig..1 also on the same scale; Figs. 4 and 5 are front views, substantially full 15 size and on a reduced scale from Figs. 1, 2 and 3, showing the magnet and pole piece assembly before and after completion; and Fig. 6 is a detail view, partly in cross section vand on a greatly enlarged scale over that of Figs. 1, 2 and 3, of the armature assembly of the o . device of Figs. l, 2 and 3. ' Referring to the drawing, 1 is a molded compo sition base of insulated material adapted to re' ceive front and rear cover plates 8 and 9 to form therewith a housing or casing for the trans 5 ducer operating mechanism. The base plate vis provided with a rear extension or shank I0 for connection with a suitable tone arm (not shown), and embedded therein are the usual electrical 30 The base is provided with two spaced depend ing leg portions vI2 and each is provided with an elongated slot or opening as indicated at I3 for" receiving a clamping screw indicated at I4 for terminal means II for the device. the interior mechanism. The clamping bolts also engage a portion of a rear cover I5forv the mech anism to hold said cover in place. On the interior face of the base,l a unitary mag net structure is provided, comprising a U-shaped permanent magnet I6> and a pole piece I1 as shown more clearly in Fig. 4. The pole piece Il is provided with welding points I8 for engag ing the poles of the permanent magnet I6 and is thereby spot welded as indicated in Fig. 5 to- pro -vide a good magnetic joint at I9, that is, a tight joint having low reluctance. The construction shown further includes in »the pole piece, two rectangular end portions in 5 dicated in Fig. 5 at Ila'. and Ilb providing a flat- surface at 22 to permit themagnet unit to be 50 seated on a magnetized device (not shown) and properly charged. The pole piece ends I'Ia and I'Ib are substantially of the same cross sectional area as the magnet I6 and between the ends the pole‘piece is recessed as indicated at 23, Figs. 55 2 _ _ ' 2,124,296 4 and 5 to provide a thin bridge portion 24 through which the air gap slot 2U is madel by cutting or milling after welding the ends to the magnet. ber 4I serves to clamp the upper end of the damper block, as indicated particularly in Fig. 2. A cover screw 43 engaging the bracket 4| through It will be seen that a unitary pole piece and magnet structure is thus provided in which the an opening in the outer cover member, as shown in Fig. 2, serves to hold the cover in position. In order that the damping block 39 may not pole piece is welded to the magnet so as to insure a good magnetic circuit at all timeseven when be under tension or compression, the clamping screwsV I4 are released slightly when the screw 40 the pickup device isgbeing serviced `in the field. The magnet acts as a bridge or yoke to maintain Y is inserted through the block. The screws I4 are a constant air gap between the severed portions of the pole piece without utilizing a special con necting link or bridge piece as has been neces then tightened to hold the assembly on the base. rThe damping block .is secured to the armature shaft by frictionV and, to provide a tight joint, the sary heretofore. 'I'he thin wall bridge portion of armature shaft end is slightly heated to cause the .material to melt and How about the shaft when the pole piece is furthermore reduced in cross sec . tion at the center on a taper forming the endV the armature ‘assembly is completed as shown in 15 sections toward the center whereby thelresulting Fig. 6. It will be seen that with this construc pole tips 25, Fig. 5 are tapered. The air gapis, tion the armature spring and damping block together with the armature spacer cushions may be therefore, substantially equal in length to the .A assembled as a unit. 20 width of the armature tail or upper Yenol herein after described. " " ' The unitary pole piece and magnet structure is provided with two tapped holes 26 to receive the clamping screws I4 through the slots i3 and per 25 mits the magnet structure 'to be adjusted‘on the base 'l‘ before ‘being finally clamped in position. A pickup coil or `winding' 2l is mounted on a flat strip of insulating material 28, which is seated against the bottom or lower .ends of the pole piece. ' The pole piece ends are also tapped to receive armature clamping screws 29, which serve to draw a clamping plate V3G against the mount ing strip 28 as shown to return the latter in` a seated position against'th’e'ends ’of the pole piece and to clamp the ends 3|-,32 of the armature pivot shaft. YThe plate orv armature Clamp 3G is of non-magnetic material, preferably of Zinc alloy. , . . ` ' ' Thearmature pivot shaft is integral with the armature`33 which 'extends through the coil 2l' and the space or large airi'gap 23, into the main or narrow air gap 20. ~ _The armature pivot shaft is surrounded by a spacer cushion -preferably of rubber in the> form of sleeves 34 whereby the armature is resiliently mounted when the clampf ing screws 22 are tightened as shown in'Fig. l. The armature pivot shaft portion 32 is tapped to receive aneedleV clamping screw 35 :and extends frontly to receive the curled en_'d of a centering 50 The pickup coil or winding 21 is provided with 20 output leads 44 `which are connected to the terminals Il, .as shown. The armature is pro vided With an axially extending recess for re ceiving a stylus or needle 45 of any suitable type and the needle is retained therein by the needle 25 screw 35 as indicated in Fig. 2. A'second unit of the construction comprises the coil 27 and mounting strip 28 therefor which'may be assembled with the magnet and pole piece structure and as a completed unit is » entirely removable from the base -lwvithout dis turbing the relation between the magnet and its pole piece and without disturbing the air gap and the flux existing in the magnetic circuit. It will' be seen that the magnetic circuit may not be broken by accidental separation of the parts and that the air gap is permanently fixed to a pre determined width. It will further be seen that with the construc tion shown, the pickup coil or winding lies within a rela'tivelyrwide air‘gap between magnetic poles 40 and theV armature extends through the coil into a relatively narrow thin air gap forming the onlylow reluctance path for the flux since the arma ture clamping plate is of non-magneticrmaterial. The pickup winding, therefore-lies within the normal flux path of the magnet and only the tip ofV the armature liesY in the main or narrow air gap.` lIthas Ybeen found that this arrangement securedthereto as shown in Figs; l, 2Vand 6 ' provides high fidelity in the translation of sig 50 particularly. The centering spring is bent at an nals from and to a phonograph record in con spring 36 which isV soldered'or otherwise suitably angle to lie across one frontal face of the pole piece to .be clamped’by a clamping piece 3l drawn in wardly to 'grip it by af’bolt >38 which is threaded intoi one of the tapped openings 25 in the pole piece. ` _ ,. SÃ; . ., VIt will be noted thatl the Yarmature clamp 30 and the -coil mounting strip 28 are slotted about 60 the clamping screw 29- to permit adjustment of nection with an audio frequency signal circuit. It will further be seen that an'advantage in the construction shown resides in the unitary magnet and pole piece construction wherein the magnet is U-shaped providing spaced poles and a pole piece having end portions welded tothe poles of the magnet to provide a low reluctance fiux path throughthe joint. ' the two members with the coil'Z'l and the arma ture 33 to center the armature tail or free end inthe fact that the magnet itself forms ayoke later in the air gap 20 as shown, particularly in for the pole pieces or pole pieceto maintain a . A further advantage in this construction lies 60 Fig. l, before tightening the> clamping member Yfixed air ‘gap without additional bridge elements. 31 by meansv of the bolt 38f »Y . ~ 'I‘he opposite or rear end ofthe armature pivot shaft *isY extended to receive a block or strip Vof inertdamping material, such as Viscoloid-,a Du Pont product, indicated at 39, one end of the strip 70 being .pressed on to the armature shaft as shown more particula'rlyinFigs. 2 and 6, with the op posite end extending upwardly to` a position wherein it isY clamped> Vagainst thelbase member 7. A vclamping screw 4l)Y extendingnfthroug‘h the base into a combined bracketY and clamping mem'-V The air gap is formed by cutting or slotting the pole piece through the thin central web after Welding to themagnet. In this manner the pole piece is prevented from becoming separated from the maghettov break the magnetic circuit, and the air gap is maintained permanently at a desired width. ` ‘ ` v Y The entire construction of the device is ar ranged to facilitate _assembly inspection and ad justment, and to lprevent impairment'of operation inthe field. 75 3 2,124,296 net and pole piece structure, a flat plate of non I claim as my invention: - » ‘ v ' l. A‘magnet assembly for an electro-magnetic transducer device comprising a magnet,- a pole piece of magnetic material united therewith by fusion of metal providing an air gap maintained permanent wholly by said magnetv as a yoke, said pole piece having a" thin bridge portion provided with a slot to form said air gap, said bridge pore magnetic material» engaging the pole piece ends in spaced parallel relation to said central web, a coil mounted on and secured to said plate between said plate and said central web, a vibratory armature extending through the coil and into the air gap, means providing a pivot shaft for the armature extending transversely of said coil support, a tion providing the onlyv magnetic conductingpath 10 yexternal to the magnet'between vthe ends .of- said pole piece, an electrical'winding within thefpole piece adjacent to ` said bridge portion, and an armature member extending through the winding and into said air gap. 15 y ~ 2. In an electro-magnetic pickup device, a uni tary pole piece and magnet structure comprising a U-shaped magnet, and a pole piece member of magnetic material extending between and welded to the poles of said magnet, said member having 20 a thin web between the poles and an air gap therein maintained fixed in width wholly by said ¿magnet as yoke, and providing the only magnetic conducting path external to the magnet between the ends of the pole piece member. 3. In an electro-magnetic pickup device, the 25 , combination with a U-shaped magnet, of a uni tary pole piece of magnetic material permanently united therewith at the magnet pole faces, said . pole piece providing a portion adjacent each pole 30 of the magnet of substantially the same cross sectional area as'the magnet and a thin unitary bridge portion therebetween of lesser cross-sec 35 clamping> plate of non-magnetic material for en- ` gaging the armature shaft, and means for adjust 10 ably-securing saidA clamping and- mounting plates to said pole piece member. , f 7. An electromagnetic pickup device comprising a UÃ-shaped magnet, a pole piece member having ends welded to the magnet poles and having a 15 thin central web slotted to provide a ñxed air gap, said magnet and pole piece thereby providing a unitary magnet and pole piece structure, a ñat plate of non-magnetic material engaging the pole piece ends in spaced parallel relation to said cen 20 tral web, a coil mounted on and secured to said plate between said plate and said central web, a vibratory armature extending through the coil and into the air gap, means providing a pivot shaft for the armature extending transversely of 25 said coil support, a centering spring for the arma ture secured at one end to one end of said pivot shaft, means for adjustably clamping the oppo site end of the armature centering spring to one end of the ypole piece, a block of vibration damp 30 ing material connected with the opposite end of said pivot shaft, a base for said pickup device, tional area, said bridge portion constituting the ' means for clamping said block of damping mate rial to said base in spaced relation to its connec only magnetic conducting element external to tion with the pivot shaft, and means for adjust-` 35 the magnet betweenv the ends of said pole piece and having a slot providing an air gap between ably securing said unitary magnet and pole piece said ends and said magnet thereby providing a yoke to hold said pole piece permanently with structure to said base member. said air gap- fixed. 4. In an electro-magnetic pickup device, the ing ends welded to- the magnet poles and having 40 combination with a magnet having poles in spaced relation to each other, of a pole piece permanently united with said poles and extending therebe tween, said pole piece providing endportions of relatively large cross-sectional area, one adja 45 cent to and contacting each of said poles, and a thin unitary bridge portion of lesser cross-sec tional area therebetween having a slot providing an air gap between the magnet poles, said magnet thereby providing a yoke to hold said pole piece 50 permanently with said air gap fixed, and said bridge portion providing the only magnetic con ducting member external to the magnet and be tween the poles thereof. 8. An electromagnetic pickup device compris ing a U-shaped magnet, a pole piece member hav a thin central web slotted to provide a ñxed air gap, said magnet and pole piece thereby providing a unitary magnet and pole piece structure, a flat plate of non-magnetic material engaging the pole piece ends in spaced parallel relation to said 45 central web, a coil mounted on and secured to said plate between said plate and said central web, al vibratory armature extending through the coil and into the air gap, means providing a pivot shaft for the armature extending transversely of said coil support, means providing a resilient bearing for the pivot shaft on op-posite sides of and adjacent to the armature, the ends of the shaft projecting axially from said bearing means, a centering spring for the armature secured to 55 5. An electro-mechanical translating device. one projecting end of said shaft, and a block of 55 comprising a magnet having poles aligned to pro vide a gap between them, a pole piece member of magnetic material bridging said gap and united at its end >portions with the magnet poles by fusion therewith, and said member having be 60 tween its end portions a thin bridge portion of `relatively small cross-sectional area providing the only magnetic circuit element external to the 65 magnet between said end and having an air gap maintained constant in width by said magnet as a yoke. . ` 6. An electromagnetic pickup device comprising posite projecting end of said shaft. 9. A transducer of the electromagnetic pickup type comprising in combination a base member 60 of insulating material, a magnet and pole piece structure comprising a U-shaped permanent magnet and a rectangular pole piece bridge across the ends of said `magnet and welded thereto to provide a low reluctance magnetic circuit, said pole piece being'recessed intermediate between ' its ends to receive a pickup winding and to pro» to provide a fixed air gap maintained permanent wholly by said magnet as a yoke and providing the only magnetic conducting path external to the vide a thin bridge between the ends of the magnet, and said bridge portion having a transverse slot and being tapered from the ends in the direction 70 of said slot to provide an air gap of predetermined width and length, an armature having one end positioned in said air gap and having an armature magnet between the magnet poles, said magnet versely on opposite sides thereof, means providing a lU -shaped magnet, a pole piece .member of mag netic material having ends welded to the magnet ~70 poles and having 'a thin intermediate web slotted 15 vibration damping material secured to the op and pole piece thereby providing a unitary mag pivot shaft integral therewith extending trans 4 2,124,296 a resilient pivot bearing for said armature shaft, an armature centering spring secured to one end of said pivot shaft, means for clamping _ said spring to said pole piece, a block of vibration damping material mounted 0n the oppositeend of said armature, means for clamping said block of damping material to the base member, and means for adjustably clamping said magnet and pole piece structure to said base member. . 10. Inran electromagnetic transducer device, a unitary magnet and pole piece structure having an air gap maintained permanent in width bythe magnet element thereof as a yoke and having a thin severed- central web providing pole tips, said web forming the only low reluctance flux path between the magnet poles, an electrical pickup winding lying within the normal ñux path of said magnet and pole piece structure, and an armature extending through the coil >and intothe air gap, said armature having a pivot shaft, an armature centering spring connected with one end of said shaft anda block of vibration damping material 10 connected with the opposite end of said shaft. EMILE C. GUEDON.