US1920789A - Film driving apparatus - Google Patents

Description

Aug 1933? c. 1 H-ElsLl-:R' 1,926,789

FILM DRIVING APPARATUS Filed Dec. 28. 1929 I ChoPLes LHeLeLer, 2 bg HLS Attorney.

Patented ug. i, 1933.

1,920,783; MLM nnrvmo srraaa'rns Charles l.. liieisler, Schenectady, N.

Y., assigner to General Electric Gompany, a Corporation ci New York Application December 28, 1929.v Serial No. 417,212

7 Claims.

My invention relates to apparatus for recording sound on a nlm or for reproducing sound from a record film. More particularly it relates to that part of the apparatus by which the lm is driven past the point at which the record is made on or at which the record is read of the film. It is the object of my invention toprovide apparatus of this character having improved means for driving the lm with the desired degree of uniformity past the'point of recording or of reproduction.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims;

Referring to the drawing, Fig. 1 is a side View partly in section of apparatus involving my invention; Fig. 2 is a cross-sectional view of thesame taken on the line 2-2 of Fig. 1; and Fig. 3 is a fragmentary view corresponding to Fig. 2 showing a modification.

While my invention is applicable both to apparatus for recording sound on a nlm and to apparatus for reproducing sound from a lm record.- I have chosen for convenience to illustrate it as forming a part of a reproducing apparatus.

The film 1 having the sound record 2 thereon adjacent to one row of sprocket holes is shownl engaging opposite sides of the same sprocket 3, suitable pressure rolls 4 and 5 being provided to hold the lm against the sprocket. Ob* viously separate sprockets may be employed if desired to engage the lm-as it approaches and leaves the apparatus and they may be variously positioned in accordance with the desired path of the film through the apparatus. From the pressure roll 4 the film passes successively in a tension loop over the control roll 6, over the 40 combined pressure and guide roll '7, around the drum 8, over the pressure roll 9, and thence in a free loop to the pressure roll 5 and sprocket 3. Both the sprocket and drum are driven from a common source of power such for example as a synchronous motor and where gearing is employed between the source and the drum, I prefer to have a ywheel secured to the shaft 10 of the drum.` The drum shaft is journaled in bearings one of which is shown at12 and inthe form illustrated the drum comprises the two coaxial portions 14 and 15, portion 14 being integral with the shaft 10 and portion 15 being detachably secured by the thumb screw 16 to the reduced extension 17 of the shaft. Within the drum is the 'xed member 19 which supports the photoelectric cell 20 and itself is supported by the bar 21 extending out through the annular gap between the two drum sections. By meansof the optical system shown at` 22 light from a suitable source is focused on the record portion of the film in the form of a narrow transverse band or line, the light after being modulated by the sound record passing on into the photo-electric cell. If desired, the drum may comprise but the one portionr 14, that 'part of the lm bearing 65 the sound record overhanging the end of the drum.

As has already been mentioned above, the sprocket and drum are connected to be driven m from the same source, preferably a synchronous motor, and if this driving connection is such that the sprocket and drum .rotate with a xed ratio relative to each other it is found in practice that the loop or the amount lof slack film between the sprocket and drum will either grow steadily larger 1 as the machine is operated or will grow steadily smaller, the nlm eventually becoming taut and being damaged. This is .primarily due to variations in film shrinkage. I have overcome this diiculty by providing aj compensator 23 which is 80 shown arranged in the drive connection to the drum, the effect of 'which isI to so regulate the speed of the drum that it moves the lm at exactlythe same speed as does the sprocket. The compensator comprises essentially a differential S5' mechanism by means of which the movement of the worm wheel 24 driven by' the worm 25 on the motor shaft rotates the drum shaft 1G at a variable speed depending upon the pressure of the brake 26 on the brake wheel 27. Through gear D0 24a and other gears, not shown, movement is transmitted from gear 24 to sprocket 3. Brake 26 is mounted on the lever 28 to which the spring 29 is attached to'apply the brake. Engaging the lever 28 is the roller 30 on the arm 31 secured to 9b shaft 32 to which also is secured lever 33 carrying roll 6. The details of the compensator construction form no part of my present invention and are disclosed' and claimed in various' forms in my Patents 1,771,922, July 29, 193.0 andx1,793.'99, 10U Feb. 17, 1931 andin my copending applications Serial No. 212,349 filed August 11, 1927, and Serial No.'34l,147 filed Feb. 19,` 1929 all of which are assigned tothe same assignee as the present ap` plication. Heretofore I have applied. aspring to the lever 33 to yieldingly hold the roll 6 against the film loop. Such a spring is shown at 25 in my above-mentioned' Patent 1,771,922. In my present construction I have dispensed with the spring and instead have applied the mass 35 to 110 the lever. By reason of its weight this mass causes f the lever 33 in response to an increase in size A ing themselves of the film loop to rotate counterclockwise keeping the desired tension in the film approaching the drum andoperating the brake lever 28 to ,f release the brake against the tension of the spring 29. In addition to the above functions which also were performed by the spring formerly employed, the mass 35 functions as an inertia device to further steady the movement of the film. Because of the mass 35 the lever 33 is less responsive to small variations in the speed of the film as feci by the sprocket such as may come from imperfect sprocket tooth action or from the gearing employed in the drive connection to the sprocket, hence the brake 26 which regulates the speed of the drum and consequently the film speed is less subject to those Variations than inthe former construction.` I prefer that the torque produced by the mass 35 be sufficient only to operate the brake lever against the spring 29 and to cause the roll 6 to exert a light pressure against the lm loop so as to follow any gradual changes that take place in the size of the loop. When such a machine is first started after being threaded with a film the lever 33 slowly moves one wayor the other for a few seconds while the parts are adjustand then appears to remain fixed during the passage of the remainder of the film.

Roll '7 mounted on arm 38 is a combined pressure roll to press the lm against the drum and a guide roll having end flanges which by engaging opposite edges of theA film prevent side weave thereof. Where the film leaves the drum it passes over the pressure roll 9 and into a free loop before reaching the pressure roll 5 and sprocket 3. It has been found that where a film is wrapped about a power actuated drum and is `pressed thereagainst bya roll which is caused to rotate through its contact with the film on the drum as in the present case, there is a tendency for the roll to retard the film with the result that there occurs a backward creepage of the film on the drum. For the proper recording and reproduction of sound, the rotation of the drum should be uniform to a high degree of precision and the film should follow the drum with a like degree of` precision. vAny creepage that occurs means that the film is slipping over the surface of the drum and this slippage is not as a steady movement but is of a rapid intermittent character. Such departure from the highly uniform movement of the drum obviously offsets to a certain extent the advantages of moving the film by the drum. Moreover it is found that when two spaced pressure rolls are employed to press the film against the drum, each driven through its contactwith the film on the drum, there often is a tendency for that part of the film between the two rolls on the drum to become enlarged or too full so that the film fails snugly to hug the drum. Thus with an arrangement of drum and light beam as illustrated results not only in a lack of uniformity of i'llm movement through the light beam but it also affects the focus of the beam on the sound record. I overcome the above mentioned difficulties and objections by causing the pressure roll 9 to be driven by means other than the film on the drum in such a manner that there is a tendency for the roll to overdrive the film, that is to move the film slightly faster than it is moved by the drum. Various means may be provided for so driving the pressure roll. In Fig. 2, Where I have illustrated by way of example a simple and effective means for this purpose, the arm 40 which is pivotally -of the two rolls 9 and 44 being corneal. That portion of the drum face which engages roll 44' is, in Fig. 2, the same diameter as those portions supporting the film adjacent the sound record. Preferably the roll 9 has a tire of soft, resilient material such as felt or rubber and the roll 44 has a hard faceadapted to resist wear. In Fig. 2 I have shown the diameter of ,the drum slightly reduced (the -showing being considerably exagi gerated) at those portions thereof which contact with those parts'of the lm removed from the sound track in order to insure the most intimate contact between film and drum adjacent the sound track. Arm 40 supporting the rolls 9 and 44 and also arm 38 supporting the pressureguide roll 7 are yieldingly held against the drum. For the best operation I prefer that the respective pressures exerted by the rolls at the beginning and the end of the film-wrap about che drum shall always have a predetermined relation with each other andin order to insure this relation I employ the single coil spring 46 which connects at its ends 105 with the two arms and at an intermediate point passes over the stud 47. Because of the difference in diameters of rolls 9 and 44, roll 9 tends to move the film faster than it is moved by the drum but since the diameter and coefficient of friction of 110 the roll 9 is greater than. that of roll 44 slipping occurs only between roll 44 and the drum. By this means it will be seenthat the film is constantly urged forward and is thereby caused rmly to hug the drum. It should be understood 115 that the tendency of the roll 9 to move the iilm forward is never so great that the film is caused to slide forward on the drum. In Fig. 3 I have illustrated a modification in which the rolls 50 and 51 corresponding respec- 120 tively to rolls '9 and 44 both are cylindrical and vthat portion of the drum engaging roll 51 is somewhat larger in diameter than the film supporting portion. In this figure the drum is shown having a uniform diameter of its filmengaging face. The construction and operation otherwise is like that of the form shown in Fig. 2.

If desired the nlm-engaging roll may be arranged so that it contacts with the lm only at one side of the sound track and in the case of a recorder where there is no necessity for the light to pass through the film the drum may be constructed to support the film for the entire width of the latter. Under certain conditions the roll 7 may be raised out of actual contact with the iilm on the drum in which case it -functions only as a guide for the film approaching the In the drawing I have purposely omitted for the sake of greater clearness a complete -showing of the enclosing casing of the apparatus, the light 140 source, the driving means for the sprocket and drum, etc. as such form no part of my present invention and are well known to those familiar with apparatus of this character.

What I claim as new and desire to secure by 145 Letters Patent of the United States, is:

1. In apparatus for recording sound on a nlm and for reproducing sound from a record film including a sprocket and/a drum arranged to engage a film at spaced points thereof, means for et, including a brake and a controlling member therefor movable in response to changes in the length of the film between the sprocket and drum and having a mass operative to maintain the controlling member in contact with thev lm and to control the pressure applied by the brake, the mass of said member serving to render the brake substantially unresponsive to sudden small variations in the speed of the film,

2. In apparatus for recording sound on a hn and for reproducing sound from a record ilm including a sprocket and a drum arranged to engage a iilm at spaced points thereof, a compensator for regulating the speed of the drum including a controlling lever therefor carrying a roll arranged in a loop in the lm between the sprocket and drum and a brake operated by said lever, said lever having a mass secured thereto and arranged to move the lever in response to gradual variations in size of the loop, said lever by virtue of the inertia of said mass being substantially unresponsive to sudden small variation in illm loop size. t

3. In apparatus for recording sound on a film or for reproducing sound from a record film including a uniformly driven drum about which the lm is wrapped and means for increasing the adhesion of the film and drum comprising tensioning means for the lm approaching the drum, and an over-driven member arranged to4 press the lm against the drum Where it leaves the same.

4. Film driving mechanism including a drum about which the lm is adapted to be Wrapped,

means for rotating the drum ata uniform speed, and means ten n' g to overdrive the'film on the drum comprising a rotatable member having one portion engaging said drum .and another portion arranged to press the nlm against the drum.

5. Film driving mechanism including a drum about which the ilm is adapted to be wrapped, means for rotating the drum at a uniform speed,

and means tending to overdrive the lm on the drum comprising a rotatable member having one portion driven by the drum and another portion engaging the lm on the d'rum and a pivotal support for said member intermediate said portions.

6. Film driving mechanism including a drum about which the film is adapted to be Wrapped, means for rotating the drum at a uniform speed, and means tending to overdrive the film on the drum comprising a rotatable member having one portion driven by the drum and another portion engaging the iilm on the drum, and means for resilientlymoving the rotatable member toward the drum including a pivotal support for the member arranged between said portions.

7. Film driving mechanism including a druml about which the lm is adapted to be wrapped, means for rotating the`drum at a uniform speed, and means tending to overdrive the i'llm on the drum comprising a shaft having at one end a roll engaging said drum and at the other end a roll arranged to engagethe film on the drum, an intermediate bearing for the shaft having a pivotal mounting perpendicular thereto and a spring actuated arm supporting said mounting.

CHARLES L. HEISLER.

CERTIFICATE 0F CORECTION.

l Patent No. l, 920, 789.

August l, 1933.

` CHARLES L. prisma.

it is hereby certified that error appears in the printed specification of the above. numbered patent requiring correction as follows: Page 3, lines 27 and 28,

- claim 3, strike out the word "including" and insert a comma; and 4that the said l with this correction therein that the same may Letters vPatent should be read Signed (Seal) Patent Office.

ll.. J. Moore. Acting Commissioner of Patente.

Images