US2173051A - Recording head and process of recording - Google Patents

Description

Sept. 12, 1939. A. DE MADALER ET AL 2,173,051

RECORDING HEAD AND PRocEsS OF RECORDING Filed Aug. 26, 1936 I 1 '19 n '53 k 1 91 :Wm

31 g I i 11 INVENTORS ATTORNEY mans... 12, 1939 RECORDING HEAD AND PROCESS or I rmcoanme Arthur De- Madaler, Bayport, and William L.

Woolf, Bayside. Long Island, N. Y., assignors to Film Recording Corporation,- a corporation of New York -'Application August 26, 1936, Serial No. 98,106

25 Claims.

device for recording a groove in a solid medium, the groove having a wave pattern with excursions from a straight line corresponding in amplitude,

frequencyandshapeto the pattern of the electric'waves forming them". When so. used this device is'known as a cutting head. It will be apparent to those skilled in the art that such a device may be used in the reverse manner, namely, to generate electrical impulses corresponding in frequency and amplitude to the wave pattern ,of a groove recorded in a? solid medium; when so used this device is commonly known as an electric v pickup. One object of this invention is to devise an instrument that will be-finore sturdy and less sub-. ject to getting out of order than those heretofore 3 available.

Another object is to devise an instrument that will form records with less needle scratch than those heretofore in use.

A still further object is to provide an instrument that records a groove of great durability permitting many reproductions with a minimum of distortion.

A'more specific object is to devise an instrument capable of making a record of good quality on a strip of film, particularly a film moving at the rate of speed commonly employed in moving picture practice, namely, from approximately 6 inches per second in the case of 16 m. m. film to 18 inches per second in the case of m. m. films.

.In this device a groove is formed by a recording point pressing into a moving medium. The 35 recording point is not movable in the direction in which the groove-carrying medium moves, but is capable of motion substantially at right angles thereto. The recording point is mounted in the end of a stylus which is rigidly connected to a rotary member. The oscillation or vibration of the rotary member causes corresponding vibration or oscillation of the recording point. To facilitate the vibration of the rotary member it is mounted on knife edges and provided with springs which restore it to its original position when displaced therefrom. Displacements are caused by thrusts transmitted through a connecting pin from a vibrating armature to a rocker arm rigidly attached to the rotary member.

0 The construction and operation of this device will be readily understood by referring to the drawing in which like numbers refer to like parts.

Figure 1 is a top view of the improved recording head.

Figure 2 is a side elevation.

This invention relates to an electro-mechanical Figure 3 is a section on line 3-3 of Figure 2. Figure 4 is a fragmentary perspective view showing the recording unit. g In this device a cutting point I is mounted in one end of a stylus 2, the other end of the 5 stylus'being rigidly attached to a rotary member 3 which is supported on knife edges 4; the rotary member 3 is held tightly against the knife edges by springs 5. A rocker arm 9, also rigidly attached to rotary member 3, receives impulses 10 from an armature M through a connecting rod l0 causing the recording point I to transcribe a wavy line on a film 24 moving on a sprocket wheel 22. The needle point I is embedded in the film to a depth of .002 inch.

In the preferred embodiment ofthe invention the recording point I is a polished diamond. The stylus 2 is designed in cross-section and made of a material to afford the maximum possible rigidity with the minimum possible mass; parm ticularly is it desirable to limit the mass of the stylus in the end remote from the rotary member. The stylus should not be subject to internal vibration but should vibrate only as a whole in unison with the rotary member which drives it. 25 In the preferred embodiment of this device the stylus is oval in cross-section, the long axis of the oval lying in the plane perpendicular to the'plane of the rotary member. This stylus is also tapered, diminishing in cross-section as it apa proaches the recording point. We have also employed hollow stylus models, and stylus models made of Duralumin as well as-steel, or Bakelite.

It is preferable to slant the stylus forward from the rotary member, the preferred angle between a thembeing approximately sixty degrees.

The rotary member 3 is formed with slots or grooves I! which bear against and provide seats ;'for the knife edges 4. Boththe slots or grooves and the knife edges are polished and hardened. o The rotary member 3 may be made hollow to reduce the mass or may be made of solid material. It has also been made from Duralumin as well as steel, wood, metal, brass, etc. Duralumin models have been v employed fitted with steel bearing 45 surfaces for the knife edges. The knife edges are held in place and supported by pins 8 which fit snugly into holes drilled into the body of the device. 'These pins may be further secured by set screws Bshown in Figure 3. In the preferred n embodiment of this device the knife edges are either complete circles or segments thereof and may be turned about the pins 8 as an axis in order to supply new bearing edges against the crushed or worn. The pins 8 are sufliciently tight to prevent vibration but loose enough to permit rotation of the knife edges by the application of sufficient force without shearing off.

In the preferred embodiment of this invention the springs 5 are curved in form and act as cantilevers. One end of each spring is attached to the rotary member 3 by screw 6. The opposite end of each spring is held by an adjustable screw 7. The springs 5 are so placed that the stresses generated in them by tightening the screws I tend to rotate the rotary member in opposite directions. In the drawing only two springs are shown. More springs may be employed, if desired. As the screws 1 are tightened the stresses in the springs are increased. By this means the vibrating portion of this device is tuned so that the natural period of the vibrating portion of the device may be tuned to any frequency desired.

In practical operation it is preferable to tune the apparatus to a high pitch.

The usual commercial loud speakers of the day through which recordings made by the device are reproduced, have a tendency to attenuate high frequencies. In order to overcome this tendency we have found it desirable to over-record the high frequencies by the same amount which the reproducer system attenuates them. This practice has an added advantage of minimizing needle scratch. 7 It is important that the springs be capable of withstanding suflicient strain to cause the system to vibrate naturally at very high frequencies. This requires a spring system of great stiffness and the requisite stifiness is provided by the construction described. By curving the springs through a wide angle as shown in Figs. 3 and 4 we have found that the resistance of the spring system to motion of the stylus is substantially proportional to the angular displacement within the limits of the displacement employed in recording, viz. about two tenths of one degree. Springs have been employed varying in curvature from 180 to 360 degrees.

The resistance ofiered by the spring mounting is consequentlyyery large compared with the force exerted on the stylus when the cutting point is cutting the groove in the record and thus the device is comparatively free from resonant peaks.

The slots or troughs I 2 may be milled across the entire length of the rotary member 3 or may be segments only near the ends of the rotary memher. If in segments care must be exercised to see that their axes lie in the same straight line. A projecting lug I3 is rigidly attached to the device and provided with threads for engaging one of the screws 1. A portion of the material of the device is cut out to provide a recess for the other adjusting screw I. An armature I4 is centered with one end mid-way in the gap provided by pole pieces I5 and I6 and the other end midway in the gap provided by pole pieces I! and I8.

It will be noted that the tightening of one of the screws i will pull one end of the armature ll to the right, while the tightening of the screw 1 in the other spring will pull that same end of the armature to the left. By a proper setting of these screws one end of the armature is centered mid-way between the pole pieces l5 and I6 and the other end of the armature opposite the connecting pin is centered between pole pieces I! and I8. By adjus ing the relative positions of the screws I the system is balanced. By tightening or loosening both screws I without changing their relative positions-with respect to each other, the system is tuned. By making the springs sufliciently long and curving them through a wide angle the stillness of the system remains constant within the limits of its normal vibration.

The rocker arm 9 which is attached to the ratary member 3 is also designed to be stiif, light. strong and free from vibration within itself so that any vibration transmitted to it by the connecting rod III is transmitted without distortion to the rotary member 3 and thence to the stylus 2. The rocker arm 9 is tapered, increasing in cross-section from the connecting rod M to the rotary member 3. It is also oval in shape, the long axis lying approximately in the same plane as the connecting rod Ill. The rocker arm may be made hollow to reduce mass. It may be made of steel or lighter material. We have employed successfully models in which the rocker arm ti, rotary member 3 and stylus 2, were all made in one piece, steel having been employed in some models and Duralumin in others.

The rocker arm 9 is placed forward on the rotarymember 3 between the springs 5 and knife edges 4, causing the stresses of vibration to be transmitted through a portion of the rotary member 3 as well as through the rocker arm ii and the stylus 2. By this means there is a. tendency to decrease the noise transmitted through the system.

The ratio of the vertical distance of the connecting rod Ill from the rotary member (which is approximately the length of the rocker arm) to the vertical distance from the recording point to the rotatry member (which is the length of the stylus time's the sine of the angle included between the stylus and the rotatry member) is of great importance. If this ratio is unity, the distance of travel 01 the end of the armature is equal to the distance of travel oi the recording needle. If the ratio is less than unity the record'- ing needle moves a lesser distance than the armature. By this means the needle may be made to move through the record medium by applying to the armature a force less than that which the resistance of the record medium offers to the needle. If this ratio is greater than unity the recording needle will move further than the armature. By this means, provided adequate recording power is available, high notes of small amplitude may be recorded which otherwise may be lost due to thetendency of the medium to flow under the needle pressure. Variations in this ratio may be made to give variations in the tone quality of the recording, and may be made to compensate for variations in the record medium. It is preferable to dampen the connecting rod ID with a piece of rubber damping material I I. The connecting rod l0 should be made of thin, light material. By making the rod sufficiently small in diameter it may be made to absorb a portion of the noise which would otherwise be transmitted' through it from the armature. The connecting ro'd must not be sufficiently thin, however, to set up vibration and noise of its own nor sufficiently thin to absorb desirable high frequencies transmitted from the armature. In the preferred embodiment of this invention the connecting pin is .030 inch in diameter.

The armature I4 is supported in position by an armature spring II.

The armature spring 3| is made sumciently rigid to prevent motion of the armature as a whole from right to left, but is flexible to rotary motion of the armature. In the preferred embodiment 01' this invention this spring is made of Phosphor bronze. This spring is held in posi- .structure of the device.

tion by screws 32 and 33 threaded into struts I1 and 38' attached to the pole pieces. Pole pieces I6 and I. on one side of the; armature are of-like polarity being attached to the same pole of the magnet 30, forming the main supporting Pole pieces I and II on the opposite side of the magnet are of like polarity, but of opposite polarity to I 6 and I8, both being attached to the opposite pole of the magnet 30. The armature I4 is surrounded by two coils l9 and 20 electrically connected to each other so that a current passing through the coils in one direction will magnetize the armature with one polarity and a current passing through the coils in the opposite direction will magnetize the armature with the polarity ,of the opposite direction, the magnetizing forces of the two coils assistingeach other. If poles I6 and I8 are south poles and if poles I5 and II are north poles and if the current is passing through the coils in such direction as to make the upper end of the armature north and the lower end south, the

- armature will tend to rotate about the spring 3| in a clock-wise direction (Figure 2) causing the recording point I to move toward the left. If. the

current through the coil is reversed the armature will be magnetized in the opposite direction and a cause it to rotate in a counter-clockwise direction, forcing'needle point I to move to the-right.

If the needle point is removed from its central position as a result of a current in the coil it will be restored to its original position by the springs when the current disappears. If an intermittent direct current or an alternating current be impressed upon the coil the cutting point I will vibrate in synchronism with the interruptions of the direct current or with the reversal of the direction of the alternating current If the current is modulated with voice or music frequencies the needle will vibrate with like frequencies and corresponding amplitudes, and cut a groove having corresponding characteristics.

In one form of this invention a thrust bearing II is provided to restrain the rotary member 3 against motion in the direction of the motion of the record medium 24. This bearingmay be formed by sharpening the forward end of. the

4 in the troughs l2 of the rotary member 3. It

is also desirable to have the springs 5 attached to the rotary member 3 by means of screws 6 on this same straight line or axis.

While this device may be used for recording on any phonographic record made of such materials as acetate, wax,-aluminum, etc., it is particularly adapted to recording on a film. When so used a strip of film 24 is threaded over the sprocket wheel 22, the perforations in the film engage the teeth of the sprocket wheel and-under the rollers 23 which-hold the film against the sprocket. As the mm 24 moves forward in the direction of the, arrow shown in Figure 4, the recording point I carves a groove 25 in the film 24. If no electrical impulses are passing through the coils I! and 20, the groove-will be a straight line, but if electrical impulses of audio Irequency pass through the coil the groove will be a wavy line having frequency and amplitude characteristics corresponding to such impulses.

' memberin one direction and the stressesinthe-r' an electro-magnet coil provided with a soft iron core and carrying direct electric current as will be well understood by those conversant with the art.

The coils I9 and 20 are prevented from pressing against the armature spring 3| by coil spacing blocks 34 held in place by screws 35.

The stiffness of the system may be understood from the following: by applying a force of one half pound to'the stylus at right angles to the rotary member 3 and at a point one half inch in vertical distance from the line joining the point of contact of the knife edges with the rotary member, the point is deflected approximately .002-of an inch. The rigidity of this system makes it very stable. These devices have been used constantlyfor several months with rough handling. and have never had to be rebalanced in any way. In this device, very high needle pressures are employed, reaching intensities of the order of 70,000 pounds per square inch. This is achieved by concentrating a pressure with a vertical component of. approximatelyone half pound on a needle point, the cross-sectional diameter of which is .003 of an inch at the surface of the medium. This point is ground at an angle of approximately 45 degrees and with, a ball point of .002 inch diameter. By forcing the needle into the medium to a depth of .002 inch the groove is .003 of an inch wide at the top. The high pressure employed on the needle point compresses the material making the groove walls very. dense and highly polished. The high polish reduces the needle scratch and the great density of the groove walls as well as the fact that the While the preferred embodiment of the invention has been described in detail, it should be understood that the invention is not restricted to the precise details here described, but may be carried out in other. ways.

Weclaim as our invention:

1. In a'recording head, a recording point, an actuating stylus therefor, a rotary member, said stylus being rigidly attached to and actuated by said rotary member, knife edges for supporting said rotary member, a plurality of cantilever springs attached to the rotary member; the stresses in a number of said springs serving to rotate the rotary member in one direction, and the stresses in the remainder of said springs serving to rotate the rotary member in the opposite direction. v

'2. In a recording head, a recording point, an actuating stylus therefor, a rotary member, mounted on knife edges -said stylus being rigidly attached to and actuated by said rotary member, a plurality of cantilever springs secured to the rotary member; the stresses in a number of said springs being disposed to turn-the rotary" remainder of said springs being disposed to turn the rotary member in the opposite direction,

means for setting the rotary member in a pre-' determined angular position with respect to the knife edges by adjusting the positions of the ends of the cantilever springs remote from the rotary member.

3. In a recording head, a recording point, an actuating stylus therefor, a rotary member, supported on knife edges, rigidly attached to and actuated by said rotary member, a plurality of cantilever springs attached to the rotary member; the stresses in a number of said springs serving to turn the rotary member in one direction, and the stresses in the remainder ot' said springs serving to rotate the rotary member in the opposite direction means for controlling the tension in the springs tending to rotate the rotary member in one direction, and independent means for varying the tension in the springs tending to rotate the rotary member in the opposite direction, permitting the tension in both sets of springs to be increased or decreased without changing their tension with respect to each other and without varying the angular position of the rotary member with respect to the knife edges.

4. In a recording head, a recording point, an actuating stylus therefor, a rotary member, said stylus being rigidly attached to and actuated by said rotary member, a plurality of 1 cantilever springs attached to said rotary member; the stresses in a number of said springs being,disposedto rotate the rotary member in onedirection and the stresses in the remainder of said springs being disposed to rotate the rotary member in the opposite direction; means for varying. the tension of said springs, said springs being capable of withstanding suflicient stress to permit the vibrating portion of the system to be tuned to any resonant frequency between 500 and 15000 cycles per second.

'5. In a recording head, a recording point, an actuating stylus therefor, a rotary member supported on knife edges, said stylus being rigidly connected to said rotary member, a rocker arm rigidly attached to said rotary member, a connecting rod attached to the end of said rocker arm opposite the rotary member, said connecting rod disposed within a plane substantially at right angles to the plane containing the rotary member, the end of said connecting rod opposite the rocker arm' being attached to an armature adapted tovibrate in unison with sound impulses.

6. In a recording head, a recording point, an actuating stylus therefor,-a rotary member supported on knife edges, said stylus being rigidly connected to said rotary member, a rocker arm rigidly attached to said rotary member, and a rubber damped connecting rod connecting said rocker arm to an armature adapted to vibrate in unison with sound impulses.

'1. In a recording head, a recording point, an actuating stylus therefor, a rotary member mounted on knife edges, said stylus being rigidly connected to said rotary member, a rocker arm rigidly attached to said rotary member, an armature susceptible to vibration in unison with sound impulses, a rubber damped connecting rod connecting said rocker arm to said armature, said connecting rod being sufficiently thin to absorb sound impulses of scratch noise frequency.

8. In a recording head, a recording point, an

actuating stylus therefor, a rotary member mounted on knife edges, said stylus being rigidly connected to said rotary member, a rocker arm rigidly attached to said rotary member, an armature suspended in a magnetic field, and surrounded by a coil adapted to vibrate at audio frequencies in unison with electrical impulses in said coil, and a connecting rod attached to said armature and to said rocker arm.

9. A device of the type described comprising two coils, electrically connected, susceptible to electrical impulses of audio frequencies, an armature suspended within said coils by a flexible spring disposed between said coils, the two ends of the armature disposed in two air gaps, each gap being formed by two poles, the two poles on one side of said armature being of like polarity, and of opposite polarity from the two poles on the opposite side of said armature; a source of magnetic energy to magnetize said poles, a rotary member supported on knife edges, cantilever springs attached to said rotary member, for restoring the rotary member to a fixed angular position, a rocker arm rigidly connected to said rotary member, a connecting rod between one end of said armature and said rocker arm, and a stylus, rigidly connected to said rotary member.

10. In a recording head, a rotary member supported on knife edges, said knife edges being circularly curved, and a recording point carried by said rotary member. v

11. In a recording head, a rotary member supported on knife edges, said knife edges being in the form of a complete circle, and a recording point carried by said rotary member.

12. In a recording head, a rotary member, a plurality of curved cantilever springs secured to said rotary member, the stresses in certain of said springs operating to turn the rotary member in one direction, the stresses in the other springs operating to turn the rotary member in the opposite direction, a stylus rigidly secured to the rotary member, and .a recording po nt carried by said stylus.

13; Ina recording head, a rotary member, a plurality of curved cantilever springs secured to said rotary member, said springs being curved through an angle not less than 180 degrees, the stresses in certain of said springs operating to turn the rotary member in one direction, the stresses in the other springs operating to turn the rotary member in the opposite direction, a stylus rigidly secured to the rotary member, and a recording point carried by said stylus.

14. In a recording head, a rotary member, a plurality of curved cantilever springs secured to said rotary member, the stresses in certain of said springs operating to turn the rotary member in one direction, the stresses in the other springs operating to turn the rotary member in the op- Y posite direction, the resistance offered by said springs to the rotation of said rotary member being approximately proportional to the angular displacement of said rotary member from its position of rest when said angle of displacement does not exceed two-tenths of one degree, a stylus rigidly secured to the rotary member, and

a recording point carried by said stylus.

15. Ina recording head, a rotary member provided with a trough and supported by a plurality of knife edges bearing in said trough, said rotary member being attached to a plurality of springs, the stresses in certain of said springs serving to rotate the rotary member in one direc m 'tion, the stresses in other of said springs serving vided with a plurality of trough segments, the

axis of which all lie in the same straight line, a plurality of knife'edges bearing in said trough segments for pivotally supporting the. rotary member, said rotary member being attached to a plurality of springs, the stresses in certain of said springs serving to rotate the rotary member in one direction and the stresses in others of said springs serving to rotate said rotary member in the opposite direction, and a stylus, carrying a recording point, rigidly secured to said rotary member.

17. In a recording head, a rotary member supported on knife edges, a rocker arm rigidly attached to said rotary member, means for impai ting vibrations of audio frequency to said rocker arm, and a stylus, provided with a recording point, rigidly secured to said rotary member.

18. In a recording head, a rotary member supported on knife edges, a rocker arm rigidly attached to said rotary member, an armature, a connecting rod, one end of which is attached to said rocker arm and the-other end of which is connected to said armature, and a stylus, provided with a recording point, rigidly secured to said rotary member.

19. In a recording head, a rotary member supported on knife edges, a stylus, provided with a recording point, rigidly secured to said rotary member, a rocker arm rigidly attached to said rotary member, an armature, a connecting rod,

one end of which is attached to said armature and the other end of .which is attached to said rocker arm at a point, the vertical distance of which to a straight line drawn between the points of contact of the knife edges with said rotary member is greater than the vertical distance from the recording point to the said line.

20. In a recording head, a rotary member supported on knife edges, a stylus, provided with a recording point, rigidly secured "to said rotary member, a rocker arm rigidly attached to said rotary member, a connecting rod, one end of which is attached to an armature and the other end of which is attached to said rocker arm at a point, the vertical distance of which to a straight line drawn between the points of contact of the knife edges with said rotary member is less than the vertical distance from the recording point to the said line.

21. In a recording head, a rotary member supported on knife edges, a stylus, having a recording point, rigidly carried by said rotary member, a rocker arm rigidly attached to said rotary member, an-armature, a connecting rod, one end of which it attached to said armature and the other end of which is attached to said rocker arm at a point, the vertical distance of which to a straight line drawn between the points of contact of the knife edges with said rotary member is equal to the vertical distance from the recording point and the said line.

22. In a recording head, a rotary member supported by knife edges, a stylus having a recording point, rigidly attached to and actuated by said rotary member, said rotary member being attached to a plurality of cantilever springs, the stresses in certain of said springs serving torotate the rotary member in one direction, and the stresses in theremainder of said springs beingdisposed to rotate the rotary member in the opposite direction, means for controlling the stresses in said springs tending to rotate the rotary member in one direction, and an independent means for varying the stresses in the springs tendingto rotate the rotary member in the opposite direction, both said means permitting the stresses in both sets of springs to be increased or decreased without varying the angular position of the rotary member with respect to the knife edges.

, 23. In a recording head, a rotary member supported on knife edges, a stylus haying a recording point, rigidly attached to and actuated by said rotary member, a rocker arm rigidly attached to said rotary member, an armature, a rubber damped connecting rod connecting said rocker arm to said armature and capable of vibrating in unison with sound impulses. said connecting rod having a diameter not greater than 30 thousandths of an inch.

24. In a recording head, a rotary member supported on knife edges, a stylus, having a recording point, rigidly secured to said rotary member, springs attached to said rotary member capable of offering a force resistant to rotary motion to the amount of eight ounces, applied one-half inch from the axis of rotation of said rotary member when the angular displacement of said rotary member does not exceed two tenths of one degree.

25. In a recording head, a rotary member, supported by knife edges, a stylus, having a recording point, rigidly secured to said rotary member said rotary member being attached to a plurality of cantilever springs, the stresses in a numberof said springs being disposed to rotate the rotary member in one direction, and the stresses in the remainder of said springs being disposed to rotate the rotary member in the opposite direction, said springs being capable of tuning to sucha stiflness that a force-of eight ounces applied perpendicularly to and one-halt inch from a line drawn through the points of contact of said knife edges with said rotary member, will not deflect said point at which said force is applied more than .002 inch.

m-rmm DE MADALER. WILLIAM L. woorr.

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