US1874101A - Cutter head for phonograph recording - Google Patents

Description

Aug. 30, 1932. R. HEAD 1,874,101

CUTTER HEAD FOR PHONOGRAPH RECORDING Filed July 30, 1929 INVENTOR fiober z f/ead,

BY g ,DW W +M ATTORNEYS Patented Au 30, 1932 UNITED @STATES PATENT OFFICE ROBERT HEAD, OF

TION or nELewAnE ASSIGNOR, ZBY MESNE ASSIGNMENTS, TO

CUTTER HEAD FOR PHONOGRAPH RECORDING Application filed July 30, 1929. Serial No. 882,254.

This invention relates to the art of phonograph recording on blank forms of wax or other suitable material capable of receiving impressions from a vibrating stylus; and more particularly relates to the stylus-bearing cutter'utilized in the actual record-cutting process. I

An object of the invention is to provide a so-called advance ball attachment forthe cutter, the purpose of which is to automatically regulate the depth of the cutting groove and thus prevent overcutting during record- 1n Tn the recording of acoustical vibrations by means of impressions made in blank forms consisting of wax or the like, it is common practice to mount the stylus-bearing cutter upon a pivotally supported arm extending axially in both directions from the point of support. The cutter is mounted at one end of the arm, and suitable weights for counterbalancing the cutter are mounted at the op osite end of the arm. The depth of the cut is regulated by so positioning the balancing weights that the weight of the cutter overbalances the weights by a sufficient amount to give a desired depth of out. If the wax form or blank, which receives the cut, is perfectly homogeneous and uniform thruout and presents a perfectly plane surface to the cutting stylus, this method of adjustment will result in approximately constant depth of cut during the entire recording process.

Record blanks are in general of sufficiently uniform density thruout as to. effect to a negligible extent the uniformity in depth of cut during recording. It is a common fault of wax blanks, however, to offer a warped or otherwise uneven surface to the cutter element which, in general, results in varying degrees of penetration of the cutting stylus.

' Thus where the above described arrangement is utilized for placing the cutter in operative engagement with the record blank, a relatively deep cut will occur as an elevation passes under the stylus and a relatively shallow cut as a depression passes thereunder. Upon reproduction of a record cut in this fashion the variations in depth of out cause corresponding variations in 'intensit of the reproduced sound or quavering e ect which is displeasing acoustically.

The present invention provides a device for overcoming this effect by ensuring" that the cutting stylus penetrates the blank to a substantially constant depth at all oints. of the recording surface regardless o irregularities in the surface thereof. This device for regulatin depth of out, which is termed an advance all consists of an adjustable support provided with a highly polished spherical or knob-like bearing surface adapted to engage the surface of the record in advance of the sound groove formed by the cutting stylus and thereby partially support the weight of the cutter. This bearing surface or advance ball, due to its blunt rounded contour, merely slides upon the surface of the blank leaving no appreciable impression thereupon. I

The advance ball is situated adjacent the cutting stylus, and is provided with means for adjusting the height thereof relative to the point of the stylus, in this way regulating the depth to which the stylus penetrates into the record. By properly adjusting the weight of the cutter carried by the advance ball support, the advance ball may be caused to ride upon the surface of'the record at all times in this manner causing the cutting stylus to penetrate the wax to a substantially constant depth at all times including the passage over elevations and depressions.

A detailed description of the advance ball attachment of the present invention will be given with reference to the drawing, of which Fig. 1 shows in perspective a standard type of electricalcutter of well-known construction having associated therewith the advance ball attachment of the presentinvention.

Fig. 2 shows a plan view of the cutter with the advance ball in position, as viewed from below in Fig. 1.

Fig. 3 shows a side elevational view of the cutter, partly in section, in position for out- CITY, NEW YORK, A CORPORA- ting a record, portions of the record blank and of the recording machine being properly,

associated therewith to indicate the mode of closure thereof is not required in describing the advance ball attachment of the present invention. The use of the advance ball attachment described herein is, of course, not limited to the particular cutter structure shown, but may, with minor modlfications, be applied to any desired type of cutter.

Referring-to the drawing, the cutter comprises a permanent horse-shoe magnet 1, a cutting stylus 2, and a casing 3 encloslng the internal structure of the cutter such as an armature 25 suitably associated with the cutting stylus and'an acoustical-frequency current-carrying coil 26, with leads 27 sultably surrounding the same for actuatmg the stylus in accordance with the sounds to be recorded. A bottom plate 18 is aifixedto the caslng 3 by means of screws 19 for further enclosing the internal structure of the cutter. Alfixed to one side of the cutter by means of screws 24; is a plate 23 provided with a cylindrical lug 4 which lug is adapted to fit into a corresponding hole of the pivotallysupported arm of the cutting machine mentioned above, after the manner indicated in Fig. 3.

The advance ball attachment comprises a hinge plate 5 affixed to the casing 3 by means of screws 6. A bar 7, preferably of metal, of sufliciently rugged structure and material to be rigid, is pivotally aiiixed at one end to the hinge plate 6 by means of the pin 8 assing thru suitable holes in the bar and inge plate. The opposite end of the bar 7 projects beyond the cutter as shown in Figs.

1 and 2, and contains a shallow centering groove 16 adapted to receive the bevelled point 15 of an adjusting screw 9. This adjusting screw 9 is screw-threaded thru a suitably drilled and screw-threaded portion 14 of a lug 12 afiixed to the side of the casing 3 by means of screws 13; The adjusting screw 9 has a knurled head 25 adapted to permit manual operation thereof for adjusting purposes. The lug 12 has formed integral therewith an outwardly projecting hook 13 having looped thereabout one end of a coiled spring 10, the other end-of which is ailixed to the bar 7 by means of the pin 11. The spring 10 is a tension spring adapted to maintain the free end of the bar 7 at all times firmly against; the point 15 of the adjusting screw, regardless of the position to which the screw is adjusted.

The bar 7, at a point adjacent the stylus 2, is provided with a knob-shaped bearing member 17 having a polished surface and a radius of curvature suitable for causing the same to ride easily over any slight irregularities in the surface of the record. The

advance ball 17 may be constructed of any suitable material, but it has been found that a sapphire is very well adapted for this purpose, since it is a hard material which takes a high polish.

It can be seen from Fig. 1 that the height with the coiled spring merely hoo ed thereover, together with the pivotal support 8, provides means for readily obtaining access to the internal structure of the cutter to replace the stylus or repair the internal structure. To accomplish this, the sprin 10 may be easily "rasped and unhooked rom the 'hook 13, a ter which the bar 7 is swung clear of the base-plate 18, thereby permitting the base-plate to be removed from the casing 3. It is believed that the two features discussed immediately above are novel to the present invention.

Fig. 3 furnishes an illustration of the manner in which the advance ball operates during the recording process. mounted on the cutting machine by inserting the lug 4 in a corresponding hole in the pivoted arm 21 associated with the machine in accordance with well understood practice. Only the portion of the ivoted arm 21 which is adapted to receive t e lug 4 is shown in the drawing; the remainder of the armbeing broken away, since the method of associating the same with the recording machine and the structure of the latter are well known in the art as shown by the patent to Quinby 1,785,047. The advance ball 17 rests upon the surface of a record 20, a portion of which is shown in section. The weight of the cutter is adjusted to cause the stylus 2 to penetrate the blank until the advance ball 17 rests upon the surface thereof the depth of the out being, of' course, determined by the adjustment of the adjusting screw 9 after the manner described above. The rotation of the blank and the radial advance of the cut ter is such that the advance ball 17 always rides in advance of the sound grooves 22 formed by the cutting stylus 2.

I claim:

1. The combination with a phono raph record cutter including a stylus, o? a rigid bar extending across the base thereof adjacent said stylus, means pivotally aflixing one end of said bar to said cutter, the other end of said bar projecting beyond said cutter and having longitudinally formed therein a shallow centering groove for reception of the bevelled point of an adjusting screw, said adjusting screw being screw-threaded thru a lug aflixed to said cutter, said lug having formed thereon an outwardly exof the advance ball 17, relative to the point The cutter is tending hook adapted for fastening one end of a coiled spring connected to said bar for holdin the same against said adjustin screw or all adjusting positions thereof, an a knob-shaped support carried by said bar adjacent said stylus and adapted to engage the surface of a record in advance of the sound groove formed by said stylus.

2. The combination with a phonograph record cutter including a stylus, of a rigid bar having one end pivotally affixed to said cutter and extending across the base thereof and projecting beyond the same, said projecting end having longitudinally formed therein a shallow centering groove for reception of one adjusting screw point, said screw being screw-threaded thru a lug affixed to said cutter, means resiliently maintaining said bar against the screw in all adjusting positions, and said bar being provided with a smooth rounded support adjacent said stylus adapted to en age a rec-- 0rd, said adjusting screw provi ing means for regulating the penetration depth of said stylus into said record.

3. The combination with a phonograph record cutter including a stylus and having a removable base plate for aifording access to the internal structure thereof, of a rigid bar pivotally afiixed at one end to said outter and extending across the base thereof to project beyond the same, said projecting end having longitudinally formed therein a shallow centering groove adaptedto receive the point of an ad usting screw, screw-threaded thru a lug aflixed to said cutter, and means for resiliently maintaining said bar against said screw for all adjustin positions thereof, said bar being provide with a rounded support adjacent said stylus adapted to engage the surface of a record, said resiliently maintaining means comprising a coiled spring aflixed at one end to said bar and having the other end looped about an outwardly extendin hook affixed to said cutter, whereby said bar may be unfastened at one end and swung clear of said base plate to facilitate removal of the same.

In testimony whereof I affix my signature.

. ROBERT HEAD.

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