US2118347A - Mechanical sound recording apparatus - Google Patents

Description

y 1938. J. J. HARDENBERG 2,118,347

MECHANICAL SOUND RECORDING APPARATUS Filed Sept. 28. 1936 Jeff/JED E/VBEEG flrrd 5 /1/15 y Patented May 24, 1938 UNITED STATES 2,118,347 MECHANICAL SOUNI I IIIESECORDING APPARA- Jan Jesayas Hardenberg, Eindhoven, Netherlands, assignor to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands Application September 28, 1936, Serial No. 103,039 In Germany September 30, 1935 '8 Claims.

My invention relates to mechanical sound re cording apparatus and more particularly to a driving device for use in such apparatus.

To insure satisfactory recording it is essen-' tial that the film be moved past the recording point at a very constant speed, and although various types of driving devices have been proposed for this purpose, such devices are unsatisfactory for mechanical recording due to the relatively large recording forces exerted on the film. If the device comprises a toothed roller to drive the film at the recording point, the speed of the film, due to the film becoming more or less wrinkled for one reason or another, will be made irregular by tooth frequencies. If intermediate driving gears are used they may introduce disturbing tooth frequencies, and in ad-. dition such gears are expensive as they must be very accurately out. On the other hand if a friction drive is used for mechanical recording,

the active surface of the friction driving wheel may become worn in spots due to the high starting forces, with the result that the speed of the film becomes irregular.

The above difiiculties are particularly severe in mechanically recording on a film, one or more sound tracks whose width variations are appreciable enlargements of the depth variations, and my invention is particularly advantageous for use in this type of recording. Such a type of recording has been described in U. S. Patent No. 1,919,116, to James A. Miller, in which a V- shaped cutting tool having an apical angle of about 174 is used, and which tool exerts upon the film a variable recording force, for instance, up to about 30 pounds per square inch. Prior recording devices using at the recording point a roller directly coupled to a flywheel driven through a mechanical filter from a driving motor do not give satisfactory results in this type of recording, because with the extremely high recording forces, the mass of the flywheel and the elasticity of the mechanical filter bring about natural vibrations which constitute a serious drawback. To eliminate this difficulty the mechariical filter would have to have the contradictory properties of being sufficiently elastic to absorb any disturbing tooth frequencies and of being sufficiently rigid to prevent the varying recording forces from causing deleterious vibrations.

The object of my invention is to overcome the above difliculties and to provide a simple and inexpensive driving device for mechanical recording apparatus by which a very uniform film speed at the recording point is insured without any flywheel. i

In accordance with the invention I drive the film at the recording point by a smooth or nontoothed recording roller driven from a driving motor through a friction drive cooperating with a large diameter driving wheel having a small mass, fixed on the shaft of the recording roller.

To eliminate any irregularities in the film speed due to uneven wearing of the friction surface, I provide two friction driving wheels driven by the motor and adapted to be selectively placed into engagement with the driving wheel. One of the friction wheels, referredto hereinafter as the starting friction wheel, engages the driving wheel only while the recording roller is being accelerated to the normal recording speed. The second friction wheel, referred to hereinafter as the running friction wheel, serves to drive the film during the recording and is adapted to en-- gage the driving wheel only after the recording roller has reached, or substantially reached, its

normal running speed. The friction wheels may be selectively placed into engagement with the driving wheel either manually or automatically and in the latter case I provide a mechanism interconnected with the starter of the driving motor, whereby operation of the starter controls the engagement of the friction wheels.

Further features and advantages of my invention will appear as the description progresses.

In order that my invention may be clearly understood and readily carried into effect, I shall describe same more fully with reference to the accompanying drawing in which:

Figure 1 is a sectionized view of a portion of a recording device embodying a driving device according to the invention.

Fig. 2 isa sectionized view of a portion of a recording device illustrating another embodiment of the invention.

Fig. 2a is a view of a portion of Fig. 1 showing a modified bearing.

Fig. 3 is a partly sectionized view of a portion of a recording device using a drivingdevice according to another embodiment of the invention.

Fig. 4 is a view along line 4-4 of Fig. 3.

Fig. 5 is a view along line 55 of Fig. 4.

The device shown in Fig. 1 comprises a rotatably-mounted shaft 2 carrying a driving wheel I and a smooth-faced recording roller 30 driving a film 3| upon which a sound track is to be mechanicallyrecorded. For clarity, the recording tool and actuating mechanism therefore are not shown but these may be of any type used for mechanical recording.

Pivotally mounted at I on a lever 32 so as to be rotatable in the direction of arrow 40 is a driving motor 5 having a shaft 4 upon which are fixedly mounted a starting friction wheel 3 having a beveled active surface cooperating with the conical surface 9 of the driving wheel, and a running friction wheel 8 adapted to engage the cylindrical surface 33 of the driving wheel. The motor 5 is preferably a synchronous motor with asynchronous starting.

Lever 32 is pivoted at 34 to a fixed support whereby the motor 3 may be moved in the direction of arrow 42 to thereby disengage wheel 3 from surface 3. Secured with one end to the upper end of the motor and with its other end fixed, is a tension spring 6 serving to hold wheel 3 in contact with the surface 9 when the apparatus is in the position shown, and to bring wheel 8 into contact with surface 33 when the motor is moved in the direction of arrow 42 by lever 32.

As shown, the device is in its starting position with the starting wheel 3 driving the driving wheel I, and when driving wheel I and roller 30 have acquired approximately normal running speed, the motor is moved by lever 32 in the direction of arrow 42 to thereby bring wheel 3 into engagement with surface 33 to thus drive wheel I during the normal running of the device.

In such a friction drive, any desired transmission ratio may be readily obtained by suitably selecting the diameters of the friction wheels and of the driving wheel, and in addition toothed recording rollers and transmission gears are dispensed with, thereby avoiding disturbing tooth frequencies. i

To decrease the driving force exerted by the wheels 3 and 3, I give the surfaces 9 and 33 of the driving wheel I a large diameter, for instance about 8 inches and preferably about 16 inches.

This also reduces the degree to which shocks or unevenness in the rotational speed of the driving wheel are transmitted to the recording roller 33 and thus reduces disturbances at the recording point. To insure an accurate mechanical sound record, the diameter of roller 30 must be above a minimum value, and thus the smallest diameter of the driving wheel to secure the above results is determined thereby.

The active surface of the running friction wheel 8 is preferably made of a flexible material, such as rubber, which materially dampens the shock and is preferably rounded to give a better frictional contact. Due to the use of the separate .starting wheel 3, such a rounded surface can be used without the danger of uneven wear thereon.

From the above it is seen that the protrusive or accelerating driving is effected only by the starting wheel 3 and thus only the surface of this wheel can be effected thereby, whereas the surface of wheel 8 will retain its circular shape.

Fig. 2 illustrates the driving device of Fig. 1 as applied to a sound-film reproducing and recording device such as is used in broadcast studios and the like. In this figure the shaft 2 carrying the driving wheel I is rotatably supported in an oblique manner by a bearing H. The shaft 2 passes through a stationary supporting plate l0 upon which aie mounted the various rollers, film spools, sound scanning device, etc. (not shown).

The weight of the driving wheel 10 is represented by the vector G having components A and B; the component B causing undesirable wear on one side of the bearing whereas component A acts on the bottom of the bearing. By using the driving device according to the invention a force C opposite in direction to force B is exerted on the wheel I and by suitably arranging the device the force C may be made equal to force B and eliminates same. Thus, only the force A remains active, which force is less than the weight as represented by vector G.

The bearing H and the cooperating portion of the shaft 2 may be tapered upward and the s aft switch of the motor. In this figure the motor 5 is mounted with the interposition of a rubber pad l2 to prevent the ,motor vibrations being transmitted to the supporting plate and recording instruments upon a supporting bracket 36 having two arms l3 fixedly secured to a rod l4. The rod i4 is rotatably supported so as to be slidable in its axial direction by two bearings l5 fixedly mounted on a suitable support. Secured to rod l4 are two disc-shaped guides l6 cooperating with a roller l1 fixed to a lever l8. (See Fig. 4.)

A spring 23 having one end fixed and its other end secured to the motor 5 exerts an upward force on the motor approximately equal to the weight of the motor and the parts; attached thereto to keep the motor floating. The spring 23 also serves to hold the friction wheel 3 against the surface 3 and for this purpose its fixed end is mounted to the rear of the plane of the drawing.

The motor 5, which is preferably a synchronous motor with asynchronous starting, receives cur-v rent through a starting switch 31 from a supply 38 into engagement with the surface 33 by the action of spring 23; the motor being rotated slightly about the axis of rod l4. This movement is effected automatically by operation of the starter 31, and for this, purpose, as shown in Figs. 4 and 5, the lever I8 is pivoted at I9 and provided at its end with a roller 20 cooperating with a spiral slot 24 in a disc 2| connected to the shaft 22 of starter 31.

As shown in Figs. 4 and 5, the roller 20 is in the circular part of the slot 24 whereby lever I8 is in the position shown in Fig. 4 and the motor and wheels 3 and 8 are in the starting position as shown in Fig. 3. Upon rotation of the starter shaft 22 into the'running position of the motor, cam 2| is turned in the direction of the arrow 46 whereby roller 20 and the end of lever l8 are moved in the direction of the arrow 41. This moves rod l4 in the direction of the arrow 39 whereby the motor is lowered, wheel 3 is disengaged from surface 9, and wheel 8 is brought into engagement with surface 33 by the action of spring 23.

While I have described my invention in connection with specific examples and applications, I'do not wish to be limited thereto but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:

1. A mechanism for driving a film at the sound-recording or reproducing point, comprising a film-driving roller, a wheel rotatable with said roller and having a driving surface, a shaft, a motor for driving said shaft, two friction wheels mounted on said shaft and adapted to selectively engage said surface, and means to move said, shaft to thereby bring one of said friction wheels into engagement with said surface only during driving surface having a diameter greater than 8 inches, a shaft, a synchronous motor with asynchronous starting for driving said shaft, two friction wheels mounted on said shaft and adapted to selectively engage said surface, and means to move said shaft to thereby bring one of said friction wheels into engagement with said surface only during starting of the mechanism and to bring the other friction wheel into engagement with said surface only during normal running of the mechanism.

3. A mechanism for driving a film at the sound-recording or -reproducing point, comprising a driving wheel provided with a large-diameter driving surface having a cylindrical portion and a conically-shaped portion, a smooth-faced filmdriving roller rotatable with said driving wheel, a driving motor, a running friction wheel driven by said motor and having a rounded surface, a starting friction wheel driven by said motor and having a beveled surface, and means to bring the beveled surface of said starting wheel into engagement with the conically-shaped portion of said driving surface only during the starting of the mechanism and to bring the rounded surface of said running wheel into engagement with the cylindrical portion of said driving surface only during normal running of the mechanism.

4. A driving mechanism for driving a film at the sound-recording or -reproducing point, comprising a driving wheel having a large-diameter driving surface, a smooth-faced film-driving roller rotatable with said driving wheel, a driving motor, a power supply system for said motor including a starting device, two friction wheels driven by said motor and adapted to selectively engage said driving surface, and-means controlled by said starting device to bring one of said wheels into engagement with said driving surface only during starting'of the motor'and to bring the other wheel into engagement with said driving surface only during normal running of the motor.

5. A mechanism for driving a film at the sound-recording or -reproducing point, comprising a driving wheel provided with a large-diameter'driving surface, a smooth-faced film-driving roller directly driven by said driving wheel, a synchronous driving motor with asynchronous starting and having a shaft, two friction wheels fixedly mounted on said shaft and adapted to selectively engage said driving surface, mounting means for said motor permitting lateral and axial displacement thereof and including a resilient member counterbalancing the weight of the motor and forcing the friction wheels in the direction of said driving surfaces, and means connected with said mounting means to bring one of said friction wheels into engagement with said driving surface only during the starting of the mechanism and to bring the other friction wheel into engagement with the driving surface only during normal running of the mechanism.

6. A -mechanism for driving a film at the sound-recording or -reproducing point, comprising a driving wheel provided with a large-diameter driving surface having a cylindrical portion and a conically-shaped portion, a smooth-faced film-driving roller rotatable with said driving wheel, a synchronous driving motor with asynchronous starting and having a shaft, a power supply for said motor including a starting device, a starting friction wheel having a beveled active surface adapted to contact said conicallyshaped portion, a running friction wheel having a rounded active surface adapted to contact said cylindrical portion, said friction wheels being fixedly mounted on said motor shaft, mounting means for said motor permitting lateral and axial displacement thereof and including a resilient member counterbalancing the weight of the motor and forcing said friction wheels toward said driving surfaces, and means connected to said mounting means and actuated by said starting device to place said starting friction wheel in engagement with the coni-cally-shaped driving surface only during the starting of the mechanism and to place said running friction wheel in engagement with the cylindrical driving surface only during normal running of the mechanism.

7. A mechanism for driving a film at the sound-recording or -reproducing point, comprising a driving wheel provided with a large-diameter driving surface having a cylindrical portion and a conically-shaped portion, a smooth-faced film-driving roller rotatable with said driving wheel, a synchronous driving motor with asynchronous starting and having a shaft, a power supply for said motor including a starting device, a starting friction wheel having a beveled active surface adapted to engage said conicallyshaped portion, a running friction wheel having a rounded surface adapted to engage said cylindrical portion, said friction wheels being fixedly mounted on said motor shaft, mounting means for said motor permitting rotational and axial movement thereof and including a resilient member counterbalancing the weight of the motor and forcing said friction wheels in the direction of said driving surface, and means to bring said starting friction wheel into engagement with the conical surface portion only during the starting of the mechanism and to bring said running friction wheel into engagement with the cylindrical surface portion only during normal running of the mechanism, said latter means comprising a cam connected to said starting device, and a member controlled by said cam and controlling the position of said motor and friction wheels.

8. A driving mechanism for driving at the recording point a film to be mechanically recorded, comprising a driving wheel having a large-diameter driving surface, a smooth-faced film-driving roller rotatable with said driving wheel, a shaft, a motor directly connected to said shaft, two friction wheels mounted on said shaft and adapted to be selectively placed into engagement with said driving surface, and means to move said shaft to thereby place one of said friction wheels in engagement with said driving surface only during the starting of the mechanism and to place the other friction wheel in engagement with said driving surface only during normal running of the mechanism.

JAN JESAYAS HARDENBERG.

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