US2272905A - Record cutting mechanism - Google Patents

Description

Feb. 10, E942. N. l.. CONRAD ETAL.

` RECORD CUTTING MECHNISM 2 Sheets-Sheet 2 Filed April ll, 1941 ill Patente Feb. 10,- 1942 asconn CU'r'rrNG MECHANISM Norman L. Conrad, Chicago, and Colin B. Dale, Oak Park, Ill., assignors tov Webster-Chicago Corporation, Chicago, ill., a corporation of Illinois Appleman api-11 11, 1941, serial No. ssaoss Y 12 claims. The present invention is concerned with a simple and dependableI record cutting mechanism which, as a self-contained unit, is adaptable to certain existing phonographs for the purpose of cutting sound grooves in a disk record whose surface -is suitably prepared for this operation. Such a device is particularly adapted for home use, and in its operations'no complications or special manipulations need be involved.

The present improvements are directed to such a unitary mechanism having special provision' against back lash arising from play or slack in the transmission; and` having a dependable Vfrictional drive in the transmission by which power is supplied to slowly advance the arm whereon the cutter is mounted.

These and other features as will hereinafter ,appear may be embodied in certain mechanisms of which two exempliflcations are set forth in the accompanying drawings in the manner following:

Figure 1, which isa top plan view of a phonograph base illustrates a record with cutting mechanism in place, also a tone arm which is swung out of the way to one side;

Fig. 2 is an enlarged detail in section taken on line 2-2 of Fig. 1;

Fig. 3 is a detail in perspectiveshowing the under side of the cutter and the adjustable spring therefor;

Fig. 4 is a fragmentary bottom plan view showing the under side of the phonograph base and motor thereon, together with one form of transmechanism; Fig. 5 is an enlarged detail in taken on line 5-5 of Fig. 4;v

Fig. 6 is asectional detail of another form of transmission which may be incorporated into the general assembly shown in Fig. 4; and

Fig. 'l is a view in section, taken on line 1-1 of Fig. 6.

Referring to Figgl, we have shown a conventional phonograph base B in the form of a platform adapted to bemounted within or upon an appropriate cabinet, portable or otherwise. Extending through the base is a spindle I0 adapted to be'received within the central" opening of a turntable T, and, according to the drive that is shown by way of example, this spindle is in frictional engagement with the turntable to establish a driving connection therefor. Upon the turntable a disk record R is adapted to be rested with its central opening receiving the spindle whereby to maintain a concentric relationship therewith.

vertical section 1 mission ,for driving the turntable and the cutter A cutter arm A is swingingly mounted atl-one side of the base, preferably near one corner, in

such a position as to rest, when inactive, within a yoke bracket II, and to extend over a record to produce sound grooves -therein when in the position shown in full lines in Fig. 1. A tone arm l2 is also swingingly mounted upon the base, being equipped, if desired, with an electric pickup I3 for tracking in the grooves of a record when swung from an inactive position (as shown) to the usual playingI position (not shown).

Any suitable driving mechanism may be employed to rotate the turntable. As shown, a center type of drive may be used, comprising an open frame F supported by and depending .from the base to expose certain meshing gears including a spur gear i5. The motor may include a stator (field) I6 and a rotor (amature, not shown) from which is extended a shaft that enters into a housing I1 wherein is accommodated certain reduction gearing, including a driven shaft I8 which extends vertically to support and drive the spur gear IB. The motor as well as the housing for 'the reduction gear all are supported by the base as by means of a horizontal plate frame I9 connected as by screws 20 with certain posts which depend from the base. f y

The mechanism described up to this point Fis entirely conventional and lforms no part of our invention. We propose to utilize, however, any of the existing drive mechanisms available for our purpose for the operative attachment thereto of the cutter mechanism which will now be explained in detail. 'I y Through the base plate, preferably at one corner as already suggested, is an vopening for receiving an elongated vertical bearing 25 adapted to extend partly above and partly below the base to which the. bearing may be secured conj veniently-as with the aid of a nut 26. This bear-- 'ing accommodates a post 21 which has capacity for turning movement therein, the upper end ofl the post carrying a head 28 which is locked fast thereto and provided with a hinge connection at 29 vfor erted radially of the hinge connection, as by a e spring 29B, will serve to prevent any play or loose the supportv of the arm A. Pressure ex-` back lash under all operating conditions.

A shield 35 of generally conical form may be fitted around the upper end of the bearing, so as to present an ornamental and'attractive appearance where it would otherwise be exposed above the base plate. Below the .base the bearing is joined to a bracket 35 which extends laterally toward the turntable drive (here shown as near the center of the'base), the bracket being provided with -a pair of depending ears 31 and 38 formed with aligned bores therethrough so as to furnish bearings for a shaft 39. One end'of this shaft, which is positioned relatively close to the turntable drive, carries a worm wheel 40 in mesh with a worm 4I on a shaft 42 whereon is mounted fast a' gear 43 that may be placed in mesh with the spur ,gear I through one of the openings in the frame E. 'I'he bracket is fixed in position' by its connection with the bearing 25 at one end and elsewhere as by a screw 45 which passes through the base for threaded connection with a boss 4B upstanding from the bracket at a point relatively remote from its fixed end. In this way motion originating with the motor is assured of transmission through the shaft 39 to its end adjacent the bearing where it carries,A a worm 41 in lmesh with a worm gear 48 having a free mounting upon the lower end of the post 21 where it is of reduced diameter. as best shown in Fig. 5.

Our invention is concerned largely with the driving connection that is established between the worm wheel 48 and the post 21 so as to provide an even and assured'flow of power free of For this purpose, we have shown two forms of transmission of which one, illustratedin Figs. 4 and 5, will first be considered.

Around the reduced lower end. of the post is fitted a friction plate 50, desirably of steel, brass, bronze, bre or other suitable material, the plate being formed with a tongue 5| upstanding from its periphery at -one point in a position which permits engagement successively with opposite I sidesl of the bracket 35 if the arm A be swung to its limit in either direction. This plate is locked to the post 21 in any convenient manner, as, for example, by swedging the post at 52. In its peripheral region the plate may be offset to provide an annular bearing surface 53 which is adapted to engage a friction disk 54 having a relatively greater c oeiiicient of friction, such as Bakelite or the like. By reason` of the peripheral offset of the plate,its frictional contact with the disk is confined to the annular offset area near the periphery of the plate. The disk is also in engagement with one face of the worm gear 48 to which it may be secured non-rotatably as by a pin 55.

The opposite face of the gear is engaged by a brake disk 55 having a relatively greater coeffinular engagingsurface offset from another friction plate in the form of a Washer 51, desirably made of or faced with steel, brass, bronze, or other suitable material. and against this washer pressure may be exerted by a coil spring 5B which surrounds the post. The spring may be secured in place as by a washer 59 which is adjustably supported on the lower threaded end of the post with the aid of a pair of lock nuts 60. One of the several elements contained in the assembly just described, preferably the friction lplate 50, is locked to the post 21, the remaining plates and disks being free. The friction plate 51 is provided with an extension arm 5l which leads to a boss 62 depending from the base plate so asfto receive therein a screw 63 which traverses the arm to secure the latter in fixed relationship to the base. In this way the plate 51 is held xedly against motion. 4

I'he cutter arm A which is swingingly mounted upon a postvupstanding from the base plate, is

desirably channeled upon its under side to accommodate a cartridge H which contains the motivating element for a cutting tool 65. At the end of the cartridge opDOsite the tool is a pair of spaced pointed lugs 55 adapted to be fulcrumed within aligned angular crotches of a plate 61 which is 'secured within the cutter arm (see Fig. 3). The cartridge is accordingly free to rock through a vertical plane about the crotches as an axis. The cartridge which is relatively heavy will tend to swing -down at its free end where the tool is positioned, and to control the'gravity force which causesithe tool to engage the record to produce sound grooves therein there is provided a ledge 68 extending rearwardly v from the cartridge at a point just above the than 1s the friction disk s4. Because of this rei lationship, the larger brake disk provides a greater area of friction surface than is afforded by the smaller friction disk 54. The frictional properties of the larger brake disk are also relatively greater than those of the smaller friction disk, and the friction surface is located at a greater radial distance fromy the center of movement, so that there is an overbalancing of frictional resistance on the side'of the worm gear which is engaged by the larger brake disk 55.

In engagement with the brake disk is an ancrotch (see Figs. 2 and 3); one end of a coil spring 59 is `connected to the ledge, its opposite end 10, which is bent in the form of an eye, being tted around the threaded shank 1I of a screw having a knurled head 12. One. end of the shank 13, which is pointed, is journalled within a bearing 14 depending from the arm'A.

the opposite end being journalled within abearing 15 that is provided in a cross plate 15 which extends transversely of the arm. Wiring connections 11 extend through the arm into the cartridge to transmit electrically thereto the sound vibrations that are to determine the character of the grooves produced 'in the record by 8B may be varied. thereby aectingthe counter` force vof the spring 69 which acts upon the cartridge to control the pressure with which the tool is tracked -in the record.

In Figs. 6 and I we have shown a modified brake mechanism which will now be described.A

Insofar as the parts illustrated in Figs. 6 and '1 are the' saine as those shown and described in4 connection with Fig. 5, they carry corresponding reference numerals.

The post 21 which extends through the bearing 25 is-providedwith a friction plate Il connected I fast thereto and formedy adjacent its periphery with a lug 8l to which is connected one end 82 worm gear 48.

vof a tension spring 83 whose opposite end 84 is fastened to a screw 85 which takes into a boss 88 depending from the bracketBB. .The friction plate 80 is engaged on its under surface bya friction disk 90 against which bears one face of a.

When the cutting tool engages-with 'a record,

several forces are set in motion which produce a condition that is dealt with very effectively by the mechanism of this invention. .With the record rotating in the directionvindicate'd by the arrow in Fig.- l, the force that is required for the tool' to plow a groove in the record is exerted on the cutting arm A in the direction shown by the arrow along the line a which is tangent to the radius of the cut. This force operates on a moment arm indicated by the line b tending to swingthe cutting arm toward the center of the record. This swinging movement becomes less as the tool draws nearer to the center of the record until, at the end of the cut, with the needle at c, the

moment arm is of the length shown by the line d.

This force, however, assures maintenance of a firm contact between the one setof interengageable faces of the teeth on the worm wheel 41 and with the mechanism srown in Figs. s and 1, the spring 83 exerts a torque on the shaft in the same direction, tending to make more intimate the contact between the interengaglng faces of the teeth already referred to. There is also at times a further force produced bythe cut grooves in the recordV occasionally tangling and .reacting on the cutting tool with the result that there is a tendency to pull the arm A toward the center. When several threads are thus tangled, this force may become considerable. With the spring mechanism shown in Figs. 6 and 7, any such force simply combineswith the other forces already noted to make the facial contact between the teeth of the worm wheel and worm gear more ins timate.

With the springless type of drive shown in Fig. 5, there is at all times a brake friction which retards the floating worm gear 48. This compels the worm wheel 41 to pull this gear so as to in- 'crease' the intimacy of contact between oneset of the faces of the interengaging teeth `on the worm wheel and worm gear. To this is added the force resulting from plowing of the groove in the record, also any torsion force tending to pull the cutting arm A toward the center, so that the value of the braking eiect of the smaller friction disk '54 should desirably be high enough to prevent these combined forces, resulting from plowing of the groove and inward swinging of the cutting arm, from setting up any back-lash from the Ainterengaglng teeth. This high value of brake effect which is afforded by the mechanism cut. tion, i. e., that which obtains between thesmallerl load which continues while the record is being On the play-back, however, another fricfriction disk. 54 and the worm gear 48, is added to the motor load, but this is less than isthe fric-V tion obtaining between the larger brake4 disk 5l and the same worm gear. It follows, therefore, that the amount of extra load put on the motor,

by the friction developed through engagement of the smaller friction disk 54 with the worr'r gear 48, will not compensate for the reduction in'motor speed which will take place when the groove Ebeing cut in the record.

The spring type of mechanism (Figs. 6 and '1) eliminates brake friction while cutting of the record proceeds, and the only load on` the motor is that which is produced by the cutting needle plowing the groove. On the play-back, however, the cutting arm A is usually set back out of the way upon the bracket I l, so that the friction disk 90 automatically becomes a brake the value of which'can be so adjusted, by manipulation of the nut 60, as to impose on the motor a load which is approximately equal to` the load of the cutting tool. It is manifest, therefore,l that by the means herein disclosed we have provided effectively for elimination of play or back-lash-an important consideration because of imperfect reproduction of sound which would otherwise result.

1. In a phonograph havingl` a rotatable post adapted to carry a cutter arm,'a power transmission in connection with the post comprising a friction plate in fast connection therewith, a second Afriction plate having av loose mounting on the post,'a xed connection for the second plate, a pair of friction disks loosely mounted on 'the post, one engaged by each plate, and a gear wheel loosely mounted on the post receiving engagen ment from the two disks' whereby rotation is'imparted from the gear lwheel to one diskan'd .thence to the plate in fast connection with tl'e post and a brake action-is. imparted by the A'other plate acting through the other disk, thence through the gear wheel, the remaining disk, and through the plate in fast connection withv the post.

2. In a phonograph having a rotatablevpostl adapted to carry a cutter arm, a power trans- Y assembly of plates, disks and gear wheel wheref by to enhance the frictional connection therebetween.

3. In a phonograph having a rotatable post adapted to carry a cutter arm, a power transmission in connection with the post including a pair of plates mounted on the post, one in fast under discussion is added to the motorload at a time when the cutting tool is in action.

It is always desirable to play back a record at approximately the same speed as it was turning at the time the sound grooves were formed therein. With the springless brake device of Fig. 5, there is applied to the motor one heavy friction connection therewith and the other loose thereon, a xed connection for the loose platea gear wheel loosely mounted on the post betweenthe plates, spring means urging the loose plate toward the gear wheel and the gear wheel toward the fast plate whereby to establish a frictional drive between the gear wheel and the fast plate. and means for positively driving the gear wheel whereby to transmit therefrom through the fast plate al friction drive to the post while receiving y from the loose plate a sustained braking action to prevent back lash.

4. In a phonograph having a rotatable post toward the fast element, and means for positively driving the gear wheel whereby to transmit therefrom through one set of elements, including the one which is fast on the post, a friction drive to rotate the post while receiving from the loose element which is -xed a sustained braking action to prevent back lash.

5. In a phonograph having a base and a rotatable post adapted to carry a cutter arm, va

transmission including a disk mounted on the, 1 post and locked thereto, a gear wheel mounted to rotate freely on the post and engaged on one side by the disk, a second disk engaging the opposite gear wheel side mounted freely on the post4 and having an anchorage with respect to the base,.and spring means exerting a thrust axially of the post upon the disk-gear wheel-disk assembly thereon for'maintaining a substantial friction therebetween whereby a driving force imparted to the gear wheel will be transmitted through the locked disk to turn the post.

6. In a phonograph having a rotatable post and a motor, a transmission for establishing a driving connection 4between the motor and the post comprising a gear wheel freely mounted on the post, a pair of friction disks in engagement with opposite faces of the gear, a pair of friction plates in engagement with the disks, `means establishing a fast connection between one of the plates and the post, and means connecting the other plate iixedly with the base whereby the gear which is frictionally engagedby the adjacent disks will serve to transmit therethrough rotary motion to the Ipost free of backlash.

7. In a phonograph having a basea rotatable post and, a gear wheel freely mounted on the post, a power transmission in connection with the gearwheel, a friction drive between the gear wheel and post, a pair of. friction disks freely mounted on the post one on each side of the gear wheel in engagement' therewith, means establishing a, fast connection between one disk and the gear wheel, a pair of friction plates, one in engagement with each disk, means establishing a fast connection between one plate and the post, and means establishing a fixed connection between the other plate and the base,

whereby when rotation is imparted to the gear wheel, a friction drive is established to the post through the medium of one friction disk and' tatable post, a power transmission-in connection with the post including a gear wheel and a plurality of interengaglngnfriction plates and disks assembled operatively therewith, the disks having engagement with opposite faces' of the gear wheel and the plates having peripheral offsets to define annular surfaces of relatively small wit-h the post including a gear wheel and a plurality of interengaging disks and plates assembled operatively therewith, means connecting one of the disks with the gear wheel, means connecting the plate adjacent the last named disk with the post, means connecting the other plate with the base, the engaging surface of the plate connected to the post being of less area and at a'lesser radial distance than the engaging surface of the other plate, and means exerting a thrust pressure upon the gear wheel-disk-plate assembly to enhance the frictional connection therebetween.

10. In a phonograph having a base and a rotatable post, a power transmission in connection with the post including an assembly of friction elements and agear wheel mounted on the post, oneof the` elements of maximum .friction value being anchored fixedly relative to the base and i another of` lesser friction ,value being connected fast to the post, and means acting to maintain the wheel-friction-element assembly in frictional driving relation.

11. In a phonograph having a base and a rotatable post, a power transmission in connection with the post including a gear wheel having a free mounting thereon, a friction' plate mounted on the post and fast thereto,.a friction disk freely mounted on the post between the plate and gear wheel and in engagement with each, means acting to maintain the plate-wheel-disk assembly in frictional driving relation, and spring means exerting a torsional force against the friction plate and post connected therewith in opposition to a power force transmitted thereto through the gear wheel.

l2. In a phonograph having a base and a rotatable post, a power transmission in connection with the post including a gear wheel having a free mounting thereon, and a friction element connected fast with the post and in engagement g with the gear wheel, means for maintaining the friction element and gear wheel in driving rela-l tion, and means applying to the friction element a torsion force in opposition to the driving force transmitted thereto by the gear wheel.

' NORMAN L. CONRAD.

COLIN B. DALE.

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