US2257466A - Sound recording apparatus - Google Patents

Description

P 1941- H. A. HOWELL 2,257,466

SOUND RECORDING APPARATUS Filed March 25, 1940 INVEN OR.

be readily made.

Patented Sept. 30, 1941 SOUN D RECORDING APPARATUS Hugh Howell, Berwyn, 111., assignor to Frank Raffles, Chicago, Ill.

Application March 25, 1940, Serial No. 325,766

2 Claims.

This invention relates to sound recording and reproducing apparatus in general and more particularly such apparatus as is used for making dis'c type phonograph records and for reproducin the sound recorded on such records. In

sound record.

One class of machines for making disc type sound records consists of a cutting stylus mounted at the end of a swinging arm which is'so ar ranged in relation to a turn table upon which the recording disc is located that the arm moves radially at a rate which bears a fixed relationship to the rate of rotation of the turn table. To effect this type of motion there is provided a speed reducing gearing interconnecting the recording arm with the turn table. Such apparatus requires high accuracy in manufacture and is,

therefore, quite expensive. Suchapparatus cannot be readily and economically changed to effeet a different speed relationship between the radial movement of the arm and the angular movement of the turn table. For some typesof recording it is advisable that such change may For instance, for recording speech it is quite possible to make the grooves in the disc typerecord very close together, thereby producing a comparatively long playing record. n the other hand, for recording music, particularly orchestral music, a greater spacing of grooves is desirable in order to allow for the production of the necessary high range of volume.

It is one of the objects of the present invention to provid a mechanism for moving the tone arm radially of the turn table in such a manner that changes in rate of speed can be readily effected.

It is a further object of the present invention to provide a recording apparatus having a grooved record guiding disc so located with respect to'the record cutting head that the grooves in the guiding disc can not possibly become clogged by shavings from the record being formed. i i

The attainment of the above and further objects of the present invention will be apparent from the following specification takenin conjunction with the accompanying drawing form ing a part thereof.

table.

Figure 3 is a bottom plan view of the turn table ofFigure 1. H i Reference may now be had more particularly to Figuresl and 2 of the drawing. "The operating mechanism is mounted on a plate I that is secured to a cabinet 2 in any desired manner,

as by a number of screws 3. A constant speed electric motor 4 is mounted on the underside of the plate I, and through a suitable speed reducing gearing 5 turns a driving pulley 6 which is in engagement with-the rim 1 of a turn table 8 that is mounted on theplate I for'rotation about an axis 9 comprising a stationary circular pin. The turn table 8 rests upon a boss I 0 which includes a thrust bearing for the turn table. The turn table may be removed bodily fromthe'plate I by lifting the turn table vertically. The turn table includes a record receiving top surface I3 and has an ofi center pin .14. A disc type record l5 may be placed upon the surface [3. The record l5 has a central hole through which thepin 9 passes, and has another "hole throughwhich the pin 14 passes, thus positively holding the record against shifting upon the turn table. The record disc l5 may be of any of the well known types of thermo-plastic or other smooth material adapted to have a sound groove formed therein and sufficiently strong for a very'large number of play.- backs. The record disc is not Dre-grooved.

A guiding disc I8 of brass'or other metal is removably secured to the underside of the turn table 8 in any desired manner, as by a plurality of screws I!) that thread into holes in the rim of the turn table, with the heads of the screws lying in countersunk holes in the guiding disc I8. The guiding disc l8 has a spiral groove 20 formed on the bottom or exposed surface thereof. This spiral extends from a point 22 a short distance from the center of the disc-to a point 23 adjacent the outer periphery of the disc; The disc I8 has a central hole 25 of a diameter exceeding. that of the boss I!) so that'the disc I8 is not required to bear any of the thrust of the weight of the turn To remove and replace the disc 18 it is merely necessary-to lift the turn table, thus removing the turn table from the plate I. It is then a simple matter to unscrew the screws l9.

An electro-magnetic cuttinghead 39 or sound impressing head; of a wellknown construction and having a cutting needle 3|, is provided for cutting a spiral sound groove into the record 15 and impressing that sound groove with a sound track. The electric cutting head or record impressing head 30 is mounted at the nd of an angle bracket 3| pivoted at 32 to a support 33.

The support 33 has a circular shaft 34 secured thereto and extending into a bushing 35 provided with a thrust bearing 36 so that the support may be oscillated about the axis of the shaft 34.

A U-shaped guiding arm 40 is pivoted at 4| to the support 33 and carries a guiding pin or needle 42 at one end, said pin being removably secured by a screw 43. The opposite end of the U-shaped arm 40, indicated at 45, extends up to and terminates adjacent the bracket 3|. A leaf spring 46 is secured to the underside of the support 33 by a screw 4'! and bears at its free end 48 against.

the arm 40, constantly urging the arm to rotate about its pivot 4| in a clockwise. direction to maintain the needle 42 in engagement with the spiral groove 20 on the guiding disc I8. When the cutting head 30 is lifted away from the record receiving surface of the turn table by pivotal action of the bracket 3| about the pivot 32, the first small upward movement of the cutting head is of 'notefiect upon the end. of thearm 40. This provides a small amount of lost motion in a vertical direction between the cutting head 3|! and the guiding arm 40. After the needle 3| has been elevated a small amount, of the order of one-quarter or one-eighth of an inch, a further upward movement of the cutting head 30. causes the end '50 of the bracket 3| to engage the end 45 of the arm 40 and swing the same in a counterclockwise direction about the pivot 4|, and against the tension'o'f 'theleaf spring 46 This causes the.

needle 42 at the end of thearm 40 to move out of engagement with the guiding disc l8. The support 33 may then be turned about the shaft 34 as a center to bring the cutting head out of position over the turn table and thus permit in.- -'sertion or removal of a record upon the turn table. Likewise, when the cutting head 30 is moved from the dotted line position shown in Figure l to the full line position, the cutting head 3Bis maintained elevated above the turn table by an amount such that the needle 42 is maintained below and out of contact with the guiding disc l8.

' As the cutting head is lowered to bring the needle 3"] into engagement with a record l5, this lowering action causes the end 50 of the bracket 3| to permit the spring 46 to swing the arm 40 to bring the needle 42 into engagement with the disc I8.

explanation will now be given of the manner of forming a sound track upon the record disc IS. The electric motor 4 is started to rotate the turntable. Thereafter the cutting head 30 is positioned-over the disc l5 and lowered so that the needle 3| engages the disc. This operation brings the needle 42 into engagement with the spiral groove 20 of the guiding disc l8. Rotation of the turn table causes the needle 42 to ride in "the spiral groove 20 and thus turn the support 33 to move the cutting head 30 radially of the turn jtableras the record I5 is being rotated. The needle-3| thus cuts a spiral groove in the disc which spiral groove "is of the same pitch as the preformed spiral groove in the guiding disc i8. At'the same time the needle 3| is caused to vibrate, electro-magnetically, by amplified voice currents that are transmitted to the coil of the cutting head by conductors 55. The needle 3'! thus forms the sound record in the groove as the groove is being cut in the record disc. When the cutting head is lifted, a counterbalancing spring 31 becomes effective to hold the head in its elevated position. The tension on the spring may be adjusted by an adjusting screw 38.

In the preferred arrangement the sound track ing music.

is formed in the record disc l5 as a spiral from the inside to the outside of the disc, the spiral 20 on the guiding disc I 8 being preferably formed in that manner in. relation to the direction of rotation of the turn table. rotates, and the needle 3| cuts its sound track in the record I5, the cuttings or shavings of the disc l5 tend to turn radially inwardly of the groove being cut. Sincethe cutting head is being moved radially outwardlyit is constantly being moved away from the shavings formed by it, thus eliminating the need of a brush or the'like for sweeping the shavings out of the path of the cutting needle 3|. View of the present invention to form the spiral groove 20 in such a relation to the direction of rotation of the turn table that the groove is cut in the record disc I 5 from the outside towards the inside of the disc, if desired.

It is to be noted that the position of the guiding disc I8 is such that the groove 20 therein cannot become clogged by shavings or cuttings from the disc I5. This is a distinct advantage in that it thus permits the use of a guiding disc N3 of materials which can be worked in a simple manner. Also, it permits the formation of the grooves closer together without danger that thin shavings from the disc l5 will clog the guiding spiral 20.

The disc I8 may be readily removed and replaced by a different disc having a spiral 20 of a greater or lesser number of turns per inch radially of the disc. It has been found that for making records of the spoken voice the grooves of the spiral 20 may be much closer together than is possible for making records of music, where the volume and frequency range is greater. Thus if 'a record is to be made of spoken words a guiding disc I8 can be used wherein the grooves are closer together than in the case of a guiding disc used to guidethe recording head 30 when record- As a result,.a longer playing record is produced. By means of the present invention the guiding disc l8 can readily be replaced by one having a greater or lesser number of 'turn xper inch of length, as required for recording speech or recording music, as the case may be.

I he spiral groove '20 on the disc 18, is of a width and number f turns somewhat in excess of the maximum width or number of turns of a recording groove to be formed on a record l5. The innermost turn 22 of the spiral 23 is closer to the center of the disc than the innermost turn of the groove to be formed on the record I5. The needle 42 on the arm 40 is therefore not in vertical alignment with the needle 3|. Instead the needle 3| is at a greater radial distance from the center 9 than is the needle 42. The needle 42 is therefore "always closer to the center pin 9. than is the needle 42. As a result it is possible to make a sound groove on a record 9 which is of a diameter larger than the diameter of the turn table or of a diameter larger than the outside diameter of the disc l8.

' At 65 is indicated a standard type of electro magnetic sound pick-up which is mounted at the "end f an arm 66 pivoted at 61 in the usual manner, whereby the present apparatus may be used for reproducing sound as well as for recording sound.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. Itis, however, to be understood that the invention is not limited to the precise construction here As the turn table 8' It is, of course, within the pur-' shown, the same being merely illustrative of the principles of the invention.

, What I consider new and desire to secure by Letters Patent is:

1. In an apparatus for recording sound on a disc type record, a turn table having a record receiving surface on one side thereof and a spiral guiding groove on the opposite side, a support mounted for turning about an axis parallel to but spaced from the axis of the turn table, said support including a portion movable to a position overlying the table, a record impressing head pivoted on said support'at said overlying portion for movement towards and away from the record receiving surface, a guiding arm pivoted on said support for movement towards and away from the spiral guiding groove, said arm having guiding means movable into and out of engagement with the groove by pivotal movement of said arm on said support, spring means urging the guiding means towards the groove, said guiding means moving in said spiral groove upon rotation of the turn table and being moved by the spiral to move said arm and said support to effect a movement of the head corresponding to the movement of the guiding means in the spiral groove, and a member rigid with the record impressing head and engaging the arm responsive to pivotal movement of the head away from the record receiving surface for causing a corresponding pivotal movement of the arm to bring the guiding means out of said spiral groove.

2. In an apparatus for recording sound on a disc type record, a turn tab-1e having arecord receiving surface on one side thereof and a spiral guiding groove on the opposite side thereof, a support mounted for turning about an axis parallel to but spaced from the axis of the turn table, a record impressing head pivoted on said support for movement towards and away from the record receiving surface, a forked member pivoted on the support and embracing the turn table and having groove engaging means at the lower tine thereof, spring means urging the groove engaging means of the forked member into engagement with the guiding groove on the turn table, said record impressing head including means rigid therewith and engaging the upper tine of the forked member for moving the upper tine of the forked member downward upon pivotal movement of the head away from the turn table whereby such pivotal movement of the head causes the lower tine to move downwardly and disengage the guiding groove engaging means from the groove.

HUGH A. HOWELL.

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