US1760114A - Pick-up - Google Patents

Description

Ma-y 27, 1930. F, CAPPS ET AL l 1,760,114

PICK-UP Filed April 15, 1929 F'IG. 9 n* 4 FGJ FRANK L. CAPPS FIG. l2 F7613.`

Patented May v27?.. 1930 FFEE PATENT A FRANK L. CMPS, OF MILFORD, CONNECTICUT, AND HARRY A.. SUMMERS, OF :BROOK- LYN, NEW YORK, ASSIGNORS T0 COLUMBTA.. PHONOGRAJPH COMPANY, KNO., OF BRIDGEPORT, CONNECTICUT, A CORPORATION OF NEW YORK Application filed April 13,

This invention relates to new and useful improvements in pick-ups for electric phonographs.

An object of the invention is to provide a pick-up, the armature of which is given a free balance and at the same time has its motion damped.

Another object is to provide an armature damping means comprising a single piece or block of rubber or similar material of predetermined size, the same beingso applied and held in place that no adjustment for compression is necessary.

A further object is to provide a pick-up wherein damping means is not inserted in the air gap between the pole pieces and armature, and wherein the pole pieces present unbroken surfaces to the armature.

Another object is to provide an electric pick-up device wherein the armature is quite free to swing from side to side, resulting in a reduction in the pressure necessarily exerted by a record to secure a sidewise deection of the armature, resulting in less wear on the record.

An additional object is to provide an electric pick-up having great sensitivity.

A further importantvobject of the invention is to provide a means to give the armature more stable balance than any heretofore made, such means further giving the necessary free balance to the armature.

Still another object is to provide a pick-up in `which the damping means is given a standard size and which when coupled with the particular armature construction, provides a device which may be easily and quickly assembled, and wherein the armature may be" accurately centered and locked in place, delay,l

and expense incident to the balancing of bumper pads against one anotherfin tests to determine whether or not they are too free, too stiff, properly centered, etc., being eliminated.

` A further object is to provide a pick-up which may be manufactured and sold at low cost, the parts being so constructed that they may be easily and quickly assembled, and the pick-up itself being so sensitive that less expensive magnets than those usually em- 1929. semi No. 354,854.

ployed may be used, and yet s obtained.

The invention is shown as applied to a wellknownpick-up now -on the market. However, it is to be understood, that the invention is applicable to other forms and styles of pick-up, and that while in the following description the detailed construction, arrangement and operation will be given, the invention is not limited to the specific form shown, since many changes will suggest themselves to those skilled in the art, and reference must be therefore made to the appended claims to a definition of the limitation of the i'nvention.

Referring to the drawing Fig. 1 is a plan view of a pick-up a part of the arm or support therefor being shown;

Fig. 2 is a plan view of a pick-up disconnected from the arm and with its cover removed;

Fig. 3 is a front elevation of the pick-up shown in Fig. 2;

Fig. 4 is a longitudinal view taken along the line 4 4 of Fig. 2;

Fig. 5 is a transverse view taken along the line 5-5 of Fig. 2;

Fig. 6 is a plan view of the magnet and pole pieces, the armature and damping means being omitted; Y

Fig. 7 is a side viewof the armature removed Fig. 8 is a view taken at right angles to Fig. 7;

Fig. 9 is a View similar to Fig. 7 but showinga slightly modified form;

ig. 1() is a view-similar to Fig. 3 but showing the modification;

Fig. 11 is a View similar to Fig. 8, but showing the armature used in the structure of Fig. 10; and

Figs. 12 and 13 are diagrammatic views showing action of stiff and flexible reeds.

Referring in detail to the drawing, at 1 is shown the pick-up adapted to be mounted in a yoke such as that shown at 2 in-Fig. 1,

the yoke being carried by an arm 3 adapted "Ito be mounted for swinging movement over a turn table or other structure carrying a record.- The pick-up includes a base 4 on 1, 3 and 9) to form a closure for the parts.

Mounted on the forward portion of the base is a permanent horseshoe magnet 6 between the arms cf which are disposed pole pieces 7 and 8. The pole faces 9 and 10 in eline upwardly and the pole faces 11 and 112 are concave. Disposed within the space between the pole pieces is an electromagnetic .winding 13, in the form of a bobbin, the same being wound. upon the support 14:.

An armature is disposed within the winding 13 and comprises a body portion 15 having a head 16 substantially in the shape of a prism and as shown in the assembled view, this head is disposed in the air gap between the pole faces 9 and 10, and presents a surface to each pole face, which surface is substantially the area of the pole face. lin this connection, it is 'to be noted that the upper pole pieces taper toward the faces 9 and 10 and that the pole faces are unbroken and are not spaced from the head 16 by blocks of rubber or the like. Further, the armature comprises a pair of bearing portions 17 and 18, the bearing portion 18 being hollow and internally screw threaded, whereby a clamp screw 19 may be used to clamp a stylus'2() in the socket 21, also formed in the armature. Bearings 17 and 18 are as shown, disposed between the pole faces 11 and 12, a strip or sheet of rubber being disposed about the bearings.

Secured in the head 16 and projecting upwardly therefrom, is a flexible reed or fin 22 of metal. To serve its intended purpose, this reed must be highly flexible and we have found that a reed comprising a thin strip of brass is suitable for this purpose.

As clearly shown in Figs. 3 and 5, reed 22 is imbedded in a block or slab 23 of rubber or other vibration absorbing material, although soft rubber has been found to be v highly satisfactory. llt is clear that the block `23 is disposed within a housing, casing or carrier 2li suitably shaped to receive the block of rubber and having outwardly extending horizontal arms 25 and 26 provided with elongated openings 28 for the passage of screws 29. q'llhese elongated bpenings permit the houslng and its contents, the block of rubber, to be shifted slightly one way or the other, so as to center the armature head 16 in the air gap between the pole faces 9 and-13.

Rearwardly of the permanent magnet 6 and also mounted on the base 4 is a block 30 carrying contacts 31 and having sockets 32 to reelve plugs 33 attached to the wires 34, leading to any amplifying system. Wires 35 connect contacts 31 to the Winding 13.

In Fig. 10 a reed 36 is shown attached to the armature head 16, this reed being in the form of a T, its upper arms 37 and 38 extendin in opposite directions and being held against meente the bearings 17 and 18 and a floating ful crum point formed at the juncture of the armature head 16 and the reed 22. rllhe greatest movement of the reed or spring 22 takes place adjacent the head of the armature at the lower surface of the rubber block.

lln making this invention, it was desired to provide a balancing force which would to some extent depend on a metallic part. ll/letal springs such as would be necessary to give the desired free balance to the pick-up armature would not damp motion. Damping of the motion is necessary to improve the frequency character, and in the present instance, damping is accomplished by surrounding a balancing spring with rubber in such a manner that normal vibrations will not be heavily damped but excessive vibrations causing the spring or reed 22 (Figs. 1 through 8) or 36 (Figs. 9 and 10) to vibrate violently, will be damped in accordance with'the amplitude of their motion.

The structure shown in Figs. 10 and 11 has been found not quite as efficient as that shown inthe remainder of the gures 'llhis is duey 'to the fact that vibrations are apt to pass through the spring or reed to the point ofecentact in the supporting housing and reflect back again without completelylosing their energy inthe rubber. However, this structure (Figs. 10 and 11) has many advantages.

With the structure shown in Figs. l through 8, where the reed or spring 22 has its free end imbedded in the rubber so as to Hoat therein, the vibrations passing through the reed.

or iin are completely lost in the rubber.

A further advantage is due to the fact that the large mass of rubber is only under a slight pressure, the force necessary to maintain the armature in balance being not suficientto cause permanent deformation of the rubber. Formerly, there have been structures usin a thread or'membrane of rubber about lg lnch square which after some use is permanently reduced to about@ inch in thickness. With the present structure, a

much larger section or block of rubber isV used. This keeps the stress in the rubber below the point where permanent deforma- `tion takes place. In addition, due to the fact that a larger area ispresent for damping effeet, it is not necessary to drive the molecules of rubber through such a large hysteresis Cil loop. Reducing the size of the hysteresis loop also tends to increase the life of the rubber.

A. very important effect resulting from the present invention is that once a piece of rubber or other damping means of given material and size has been determined upon, no adjustment for' compression is necessary. The only adjustment made with the rubber is to slide the container 24 back and forth to center the armature in the air gap. Should the pick-'up subsequently become deective, it will not be due to failure in the rubber, but will be due to loosening of the screws which hold the container. 'lo correct this, it is only necessary to re-center the armature bysliding the container or housing 24, and again tightening the screws.

Magnetic leakage is also reduced due to the present arrangement, since there are not slots in the pole faces 9 and l0 to receive damping material. This reduces flux leakage and makes possible the use of narrower pole pieces with a correspondingly lighter moving member.

A further advantage flowing from this structure is thatJ the low unit pressure exerted by the rubber block 23 makes possible a more reliable adjustment. ln turn, this makes it possible to have a balance allowing the armature to freely swing Jfrom side to side. Accordingly, wear on records is decreased, since the sidewise pressure necessary to secure a given sidewlse deflection is alsodecreased.

Greater sensitivity is also obtained. rlhe low sidewise force necessary for a given deflection of the armature causes less bending in the needle point and results in less motion of the entire pick-up and its supporting arm. Therefore, more of the vibratory motion of the record groove is transmitted to the top part of the armature, thus improving the sensitivity or etiiciency of the pick-up. Heretofore, it has been readily possible to get 21- free balance with high sensitivity, but without stable adjustment. Further, it has been easy to obtain a sturdy adjustment at the sacrice of sensitivity, and at the cost of wear on the records. With the present arrangement, low sidewise force and great sensitivity is obtained due to the use of thev flexible reed and the block of soft rubber as a damping means.

ln the present instance, owing to the fact that the rubber is compressed only to a low value, there is almost no chance of any deformation in the rubber. The result is a high degree of stability of adjustment. Moreover, the motion is transmitted from the armature to the rubber through a iexible member, and therefore, the stability of adjustment obtained by using a large mass of rubber is not attained in the expense of a free Vbalance with its accompanying high sensitivity. l

'lhere is a certain advantage .resulting from the placing of the rubber blocks 23 in a housing, or casing 24. The rubber can be made suiciently close to a selected standard so that a definite size of block and a casing or housing definitely diminished to it it, may be chosen. rlhus, instead of the necessity of balancing two pads one against the other, and test the balance to make sure it is not too free, nor too stiff and properly centered, it becomes only necessary to assemble the rubber into the housing or casing and position this assembly over the spring or reed and slide the assembly to one side or the other until the armature is accurately centered in the air gap, after which, the screws 29 are tightened. y

Having thus described the invention, what is claimed is:-'

l. in an electric phonograph pick-up, an

armature mounted Jfor rocking movement about a pivot, al flexible spring member projecting from said armature and damping means enclosing the end of said spring.

2. ln an electric phonograph pick-up, lan armature, a flexible spring member projecting from said armature, and damping means enclosing the free end of said spring. g

3. :in an electric phonographpick-up, an armature, a pair of pole pieces disposed one at each side of said armature. an airgap between said pole pieces, said armature having a head disposed in said air gap, a spring member secured to the head of the armature and projecting outwardly of the air gap, and damping means engaging each 'side of the sp1-infT l member.

4c. n an electric phonograph pick-up, an armature, a pair of pole pieces disposed one at each side of the armature and having an air gap between them, said armature mounted for rocking movement about a substantially .I horizontal pivot and having a head disposed in said air gap, a spring member secured to said head and projecting upwardly therefrom out of said air gap and a damping means engaging each side of said spring beyond the air gap. i

5. ln an electric phonograph pick-up, an armature. a pair of pole pieces disposed one at each side of the armature and having an air gap between them, said armature mounted for rocking movement about a substantially horizontal pivot and having a head disposed in said air gap, a spring member secured to said head and projecting upwardly therefrom out of said air gap, and a damping means engaging each side of said spring be` yond the air gap, said damping means at its under side engaging the upper surface of said pole pieces.

6. In an electric phonograph pick-up, an armature, a pair of pole pieces disposed one at each side of the armature and having an air gap, between them, said armature mounted for rocking movement about a substantiallyed for rocking movement about a substan-- tially horizontal pivot and having a head disposed in said air gap, a spring member secured to said headand projecting upwardly therefrom out of said air gap, and a damping means engaging each side of said spring beyond t-he air gap, said damping means com.- prising a block of rubber.

8, ln an electric phonograph pick-up, an armature, a pair of pole pieces disposed one at each side of the armature and having an air gap between them, said armature mounted for rocking movement about a substantially` horizontal pivot and having a head disposed in said air gap, a spring membersecured to said head and projecting upwardly therefrom out of said air gap, damping means engaging said spring, said damping means comprising a block of rubber into which the free end of said spring is imbedded.

9. ln an electric phonograph pickup, an armature, a pair of pole pieces disposed one at each side of the armature and having an air gap between them, said armature mounted for rocking movement about a substantially horizontal pivot and having a head disposed in said air gap, a spring member secured te said head and projecting upwardly there from out of said air gap, and a amping means engaging each side of Said spring heyond the `air gap, and a housing enclosing said damping means and means to secure the yhousinf6 in placeo 10. lian an electric' phonograph pick-up, an armature, a pair of pole pieces disposed one at each side of the armature and having an air gap between them, said armature mounted tor rocking movement about a substantially horizontal pivot and having a head disposed in said air gap, a spring member secured to said head and projecting upwardly therefrom out of said` air gap, said damping means comprising a block of rubber into which the free end of said spring is imbedded, and a housing for said block and means for securing the housing in place. v

11. A device as in claim. 9, said housing be= ing laterally adjustable to center the' armature in the air gap.

12. A device as in claim l0, said housing beiearia FRANK lL. CAPPS. HARRY A. SUMMERS.

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