US2071477A - Apparatus for recording sound on or reproducing from an endless band of film - Google Patents

Description

Feb. 23, 1937. D. VON MIHALY APPARATUS FOR RECORDING SOUND ON OR REPRODUCING FROM AN ENDLESS BAND 0F FILM Filed March 21, 1935 2 Sheets-Sheet 1 Attorngyq Fb. 23, 1937. 11 VON MlHALY 2,071,477

APPARATUS FOR RECORDING SOUND ON OR REPRODUCING FROM AN ENDLESS BAND 0F FILM Filed March 21, 1935 2 Sheets-Sheet 2 Patented Feb. 25, 1937 UNITED STATES APPARATUS FOR RECORDING SOUND ON OR REPRODUCING FROM AN ENDLESS BAND OF FILM Dnes von Mihaly, Berlin-Wilmersdorf, Germany,

assignor to the firm Julius Pintsch Aktiengesellschaft, Berlin, Germany Application March 21, 1935, Serial No. 12,322 In Germany March 21, 1934 14 Claims.

This invention relates to apparatus for recording sound on a film or reproducing sound from a film record.

Many attempts have been made already to produce apparatus for recording and reproducing sounds being free from the disadvantages of the known phonographs, said disadvantages consisting chiefiy in the necessity of frequently changing the record disc and in the frequent interruptions of the sound reproduction caused by the shortness of the sound record on the disc, the loss of all very high and very low frequencies etc.

There has been developed an apparatus for recording sound on an endless band of photographic film and for reproducing sound from a record on such film in which the sound record is in the form of a plurality of separate parallel tracks on the film which tracks are running in parallel direction to the edges of the film, and are successively traversed by the recording light beam or by the reproducer, the transfer from one track to another being effected automatically under the control of the film. In this apparatus the shifting of the light beam across the film is effected either by an electromagnet controlled by a contact carried by the film or by mechanical means including a lever adapted to engage a notch in the edge of the film.

Both means for efiecting the shifting of the light beam across the film have the common disadvantage that the speed of the shifting of the light beam is depending upon the state of the shifting means in the instant of their action. Thus in case of the electromagnetic shifting the speed of the movement of the light beam depends upon the strength of the current flowing through the winding of the electromagnet which may be reduced or increased according to the temperature of the winding, the purity of the contacts in the circuit of the winding, the pressure acting upon these contacts etc.; in case of the mechanical shifting the speed depends upon the friction of the mechanical parts varying with the temperature, the wear and tear of these parts, and the quality of their lubrication, as well as upon the extent to which the notch in the edge of the film has been widened by the frequently repeated knocks of the lever engaging the notch. In consequence of the differences of the speed of the movement of the light beam across the film caused by these reasons the light beam will describe different ways on the film each time it is shifted, and therefore the sound reproduction will be interrupted at each shifting of the light beam. Provided that in order to make full use of the whole width of the film the sound tracks are arranged very near to one another, then the irregular shifting way of the light beam may even result in reproducing the neighbouring sound track for the time of the shifting.

Another common drawback of the above mentioned means for shifting the light beam across the film is that they cause frequent breaking of the film since the contact carried by the film is constantly rubbing the neighbouring windings of the rotating film-spool, while with the mechanical shifting the film gets injured by the frequent comparatively hard knocks of the lever controlling the shifting device.

The object of this invention is to provide an apparatus of the above described type, in which the speed of the shifting movement of the light beam is exactly predetermined so that the shifting ways of the light beam on the film will be exactly parallel to one another and, in consequence thereof, the light beam will always remain in exact register with the sound track during reproduction.

Another object of the invention is to shift the light beam from one sound track to the next with a speed being exactly proportional to the speed of the lengthwise movement of the film.

A further object of the invention is to derive the driving of the device for shifting the light beam from the driving means effecting the lengthwise movement of the film.

Still another object of the invention is to control the device for shifting the light beam by an electromagnet which is controlled by a contact gliding on the edge of the film and cooperating with a notch in the film. Since for securing the reliable operation of this arrangement the contact has to be pressed against the edge of the film only with moderate pressure, the film will not be injured thereby so that breaking of the film as well as Widening of the notch are avoided.

Referring to the drawings, Fig. 1 is a perspective View with parts broken away of the apparatus; and Fig. 2 is a detail thereof drawn to a slightly larger scale.

In the base plate 2 forming the cover of the housing I is at one end a circular hole 3 in which the plate 5 carrying the filmspool 4 is mounted in such manner, that its plane is inclined with respect to the plane of the base plate 2. The film-spool is supported by freely rotatable rollers 6 radially arranged on the plate 5, and also freely rotatable guide rollers 1 are provided for holding the spool in position on the plate 5.

On the other end of the base-plate 2 a drum 8 is mounted which is provided with a groove ID of a width equal to the width of the film. On both sides of this groove two slightly raised guides l l for the film are provided; and within the groove ID a vertical slit i2 is arranged, the width of said slit being about 0.02 mm. and its length be ing equal to the useful width of the film. Within the drum 8 a photoelectric cell It is mounted, said cell being connected in known manner to an amplifier and to a loudspeaker.

Between the film-spool 4 and the drum 8 there is a sprocket M which is mounted upon the axis l of the motor l5, and is driven by the motor. On both sides of said sprocket |4 spring supported pressing rolls H are provided. The endless band of film 9 is withdrawn from the inside of the coil over the roller 1' by the one side of the sprocket i4, is then led round the drum 8 to the other side of the sprocket I4 and past the guide roller l8, and it Winds up on the outside of the spool 4. By using the two sides of the same sprocket l4 for feeding the film to the drum 8 and for withdrawing it therefrom exactly uniform movement of the film round the drum 8 is secured.

Before the drum 8 there is a mask IS, the opening of which lies exactly before the slit |2 of the drum 8. The diameter of this opening 29 is substantially equal to the width of any of the sound tracks 2| on the film. The mask I9 is fastened to a frame 22 which is vertically shiftable along guides provided within the drum 8. A light source 24, f. e. an incandescent lamp, and a condenser lens 25 are secured to the lower part of the frame 22 while the mask I9 is carrying an inclined mirror 26. If the apparatus is to be used for recording sounds, then of course the incandescent lamp has to be replaced by a lightsource the light-intensity of which is variable with the strength and the frequency of microphon-currents acting upon it, i. e. by a discharge lamp.

The light of the light-source is concentrated to a light beam by the lens 25 and falls through the opening 23 of the base plate 2 upon the inclined mirror 26 by which it is reflected through the opening 20 and the slit 2 upon the film 9, and through the sound tracks of the film onto the photoelectric cell l3.

The frame 22 rests by means of the adjustable knife edge 21 upon the one end of the horizontal lever 29 which is supported by a pin 28. To the other end of the lever 29 a vertical lever 30 is pivoted, the upper end of said lever serving as the armature 3| of an electromagnet 32, and its lower end carrying the threaded head 33. This head is pressed against the screw-spindle by the spring 34. To the lower end of the axis 36 of the spindle 35 is secured the friction disc 31 against which presses the rope pulley 38 which is driven by the motor l3 by means of the rope 39. On the friction disc 31 a pin 40 is provided which is engaged by the one end of a lever 4| thus preventing rotation of the disc 31. The other end of the lever 4| serves as the armature of an electromagnet 42 in the circuit of which there is a switch consisting of the two contacts 43 and 44. The spring borne contact 43 carries a roll gliding along the edge of the film I9.

On the end of the lever 29 a contact 45 is provided, and this contact as well as its countercontact 46 are inserted into the circuit of the electromagnet 32. The distance between the contacts 45 and 46 is equal to the distance between the two utmost sound tracks on the film 9 multiplied by the ratio of the length of the two arms of the lever 29.

Now the operation of the apparatus if employed for recording sounds shall be described. In this case naturally the mask I9 is to be re placed by another one having a slit of suitable dimensions instead of the opening 20.

With the frame 22 being in its lowest position the slit 20 of the mask I9 is exactly on the level of the first, lowest sound track to be recorded on the film, and consequently the light beam passing through the opening 20 and slit 20 produces the first sound track on the film which is moved by the motor H5 at uniform speed in direction of the arrow.

When the entire length of the film but a few centimeters has been passed through the light beam and the point 4'! is reached at which the sound record should transfer to the next sound track, the notch 48 passes the contact roller 43. Thereby the contacts 43 and 44 are closed and the electromagnet 42 is energized. The left arm of the lever 4| is drawn downwards by the electromagnet, consequently the right arm of said lever disengages the pin 40, thus allowing the friction disc 3'! to be rotated by the constantly rotating rope pulley 38. The friction disc, however, can make only one revolution because the contacts 43 and 44 are instantly opened again when the notch has passed the roller 43, and therefore the lever 4| stops the friction disc as soon as the pin 40 reaches this lever again.

During the rotation of the friction disc 31 the spindle 35 is also rotated and the head 33 is pressed downwards while the frame 22 and with it the light beam is lifted until the rotation of the disc 37 and of the spindle 35, after one revolution, is stopped by the lever 4|. As the disc 3'! and the spindle 35 are driven by the film driving motor Hi, the speed of rotation of the spindle 35, and, in consequence thereof, the speed of the shifting movement of the light beam on the film is exactly proportional to the speed of the film, so that the sound track recorded during the shifting process will be a substantially straight line rising from the level of the first sound track to the level of the second sound track. The same play is repeated every time when the light beam transfers from one sound track to the next so that all bridging portions of the sound tracks will be exactly parallel lines beginning and ending at the same points of the film.

If the apparatus is employed for reproducing the sound record made in the above described manner the process is quite similar: In consequence of the dependence of the shifting movement of the light beam on the lengthwise movement of the film the light beam describes here the same parallel lines on the film as in the recording process and therefore remains in constant register with the sound tracks also at their bridging portions so that any interruption of the reproduction is avoided. As soon as the last,

highest sound track of the film has entirely passed through the light beam, and the spindle 35 is rotated again, then the contact 45 reaches the contact 46. The electromagnet 32 gets energized and attracts its armature 3| whereby the head 33 is disengaged from the spindle 35. Then the frame 22 is lowered by the action of the spring 49 and, the circuit of the electromagnet 32 having been interrupted again at the contacts 45, 46, the head engages the spindle 35 again at its highest part so that the sound record is automatically reproduced again from its beginning.

The reduction of the transformation of the movement of the head 33 to the frame 22 by means of the reducing lever 29 has the advantage that the thread of the spindle 35 and of the head 33 need not be made so fine as it were necessary for directly shifting the frame by the width of a sound track (i. e. 0.5-0.1 mm.) but the thread can be made coarser and accordingly cheaper. Moreover the reduction makes it easier to overcome the inertia of the movable parts; and finally it enables to adjust the movement of the frame corresponding to one revolution of the spindle 35 by means of the screw 50, thus making it possible to pay regard to any reduc tion of the original distance of the sound records due to the shrinkage of the film.

By closing the contacts 43, 44 by hand by means of the button the light beam can be focused on any desired sound track. The same effect can be obtained by means of a handle secured to the lever 4| and projecting beyond the housing I, said handle enabling to lift the lever 4|, thus allowing the spindle 35 to rotate as long I as the light beam reaches the desired sound track.

Instead of the shiftable mask 19 naturally also other movable optical devices may be used for shifting the light beam on the film, like adjustable mirrors or prisms. The relative movement between the film and the light beam may also be effected by shifting the film instead of the light beam.

Having now particularly described and ascertained the nature of my invention and in what manner the same is to be performed I declare that what I claim is:

1. In apparatus for recording sound on or reproducing sound from an endless band of film having a plurality of photographic sound tracks running substantially in parallel to the edges of the film, means for directing a narrow light beam on the film, means for driving the film in lengthwise direction, and means for causing intermittent relative movements between the film and the light beam in a direction transversely of the film at a constant speed proportional to the speed of the lengthwise movement of the film at each complete passage of the endless band past the light beam.

2. Apparatus according to claim 1, in which the force for effecting the transverse relative movements between the film and the light beam is derived from the means for driving the film in lengthwise direction.

3. In apparatus according to claim 1 said means for driving the film in lengthwise direction comprising a motor, the means for causing the transverse relative movements between the film and the light beam being driven by said motor.

4. In apparatus according to claim 1, an electromagnet for controlling the operative connection of the means for causing the transverse relative movements between the film and the light beam with the means for driving the film in lengthwise direction, and a switch in the ciruit of said electromagnet, said switch being adapted to be controlled by a notch or perforation in the film.

5. In apparatus for recording sound on or reproducing from an endless band of film having a plurality of photographic sound tracks running substantially in parallel to the edges of the film, means for directing a narrow light beam on the film, a motor for driving the film in lengthwise direction, and means including a spindle adapted to be driven by said motor for causing intermittent transverse relative movements between said film and said light beam at a constant speed proportional to the speed of the lengthwise movement of the film at each complete passage of the endless band past the light beam.

6. In apparatus for recording sound on or reproducing from an endless band of film having a plurality of photographic sound tracks running substantially in parallel to the edges of the film, a motor for driving the film in lengthwise direction, an electromagnet, means controlled by the film for controlling said electromagnet, means including a spindle connected to and driven by said motor for causing transverse relative movements between said film and said light beam, a friction coupling between said spindle and said motor, and means operated by said "electromagnet for normally preventing movement of said spindle.

7. In apparatus for recording sound on or reproducing from an endless band of film having a plurality of photographic sound tracks running substantially in parallel to the edges of the film, optical means for directing a narrow light beam on the film, a movable support carrying said optical means, a motor for driving the film in lengthwise direction, and means including an adjustable speed reducing device for shifting said support in a direction transversely of the film, said shifting means being connected to and driven by said motor.

8. In apparatus for recording sound on or reproducing from an endless band of film having a plurality of photographic sound tracks running substantially in parallel to the edges of the film, optical means for directing a narrow light beam on the film, a movable support carrying said optical means, a motor for driving said film in lengthwise direction, a screw-threaded spindle, a friction coupling connecting said spindle to said motor, means for checking said spindle, means controlled by the film for intermittently releasing said checking means, a screw-threaded claw engaging said spindle, and a lever operatively connecting said movable support to said claw.

9. In apparatus according to claim 8, a knife edge secured to said support and resting upon said lever, and means for adjusting the position of said knife edge upon said lever.

10. In apparatus according to claim 1, means for automatically shifting said light beam from its position in which it registers with the last sound track on the film back to its position in which it registers with the first sound track of the film, after the entire length of the last sound track has passed through said light beam.

11. In apparatus according to claim 8, means for automatically interrupting the engagement of said claw with said spindle for a short time after said claw has reached one of its extreme positions on said spindle.

12. In apparatus according to claim 8, an electromagnet adapted to disengage said claw from said spindle, and a switch in the circuit of said electromagnet, said switch being operated by said means for shifting the support of said optical means so as to be instantaneously closed when said shifting means reach a position in which the light beam would have the useful portion of the width of the film.

13. In apparatus according to claim 6, means for releasing said checking means by hand.

14. In apparatus according to claim 6, a handoperated switch in the circuit of the electromagnet for operating said checking means.

DENES voN MIHALY.

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