US2705640A

US2705640A - Sound motion picture apparatus

Info

Publication number: US2705640A
Application number: US224696A
Authority: US
Inventors: Valle Guillermo A Del
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1951-05-05
Filing date: 1951-05-05
Publication date: 1955-04-05
Anticipated expiration: 1972-04-05

Description

G. A. DEL. VALLE ISOUND MOTION PICTURE APPARATUS April 5, 1955 3 Sheets-Sheet 1 Filed May 5, 1951 ATTONEY April 1955 G. A. DEL VALLE SOUND MOTION PICTURE APPARATUS 3 Sheets-$heet 2 Filed May 5, 1951 Eufllermn H. 35%311:

ATTORNEY April 5, 1955 e. A. DEL VALLE SOUND MOTION PICTURE APPARATUS 5 Sheets-Sheet 5 Filed May 5, 1951 INVENTOR Guillermu H, del Valle ATTORNEY United States Patent SOUND MOTION PICTURE APPARATUS Guillermo A. Del Valle, Merchantville, N. 1., assignor to Radio Corporation of America, a corporation of Delaware Application May 5, 1951, Serial No. 224,696

3 Claims. (Cl. 274-4) The present invention relates to sound motion picture apparatus and more particularly to mounting means for sound translating devices used on such apparatus.

In the motion picture art, a film has been developed bearing a magnetic sound track which has demonstrated desirable characteristics. However, in order to use this type film, conventional machines must be modified to the extent of incorporating a magnetic transducer in the sound system. Since some of the film used on these machines will be of the type bearing the magnetic sound track and some will be of the type bearing the conventional optical sound track, the modification of conventional machines to adapt them to use with the magnetic sound track should not be such as to prevent the machines from being used with the conventional or optical sound track. A system suitable for use with either type film is shown and described in a copending application to Masterson, Ser. No. 124,470, filed October 29, 1949, now Patent No. 2,605,364, issued July 29, 1952.

In that application there is described and claimed a sound system in which a magnetic transducer and a mirror are mounted on a bracket which is secured to the machine in a position surrounding a sound drum. The mirror and the magnetic transducer are spaced about the bracket by substantially 90. The two elements are selectively moved into operating position by rotating the bracket through the 90 angle. In that system, when the transducer is in its operating position, the assembly is sub stantially rigid. That is to say, the relative radial position of the transducer with respect to the outer surface of the sound drum is fixed. In the operation of the machine, the film is drawn around the sound drum so that the sound-track portion of the film overhangs the rear edge of the drum. Since the film is usually made of a flexible plastic, the unsupported sound-track frequently develops imperfections in the form of waves or undulations. If the relative position of the transducer and the sound drum are fixed, these waves will cause variations in the spacing between the sound-track and the transducer which may be converted into undesirable amplitude variations in the signals.

Accordingly, it is an object of the present invention to provide an improved sound system for motion picture apparatus suitable for use with film bearing a magnetic sound-track.

It is another object of this invention to provide an improved sound system as set forth characterized in that means are provided for resiliently supporting a magnetic transducer in a position for engagement with the magnetic sound-track of a film.

A further object of the present invention is to provide an improved sound system as set forth which is selectively adaptable for use with film bearing either a magnetic or an optical sound-track.

Still another object of this invention is to provide an improved mounting means for a magnetic transducer.

It is a still further object of the present invention to provide an improved mounting means as set forth characterized in that the transducer is resiliently supported.

Yet another object of this invention is to provide an improved mounting means as set forth characterized in that a transducer supported thereon may be adjusted with respect to the sound-track on the film.

In accomplishing these and other objects, there has been provided, in accordance with the present invention, a mounting bracket secured to the main body of a motion 2,705,640 Patented Apr. 5, 1955 picture machine adjacent to the sound drum thereof. An arm is mounted on the bracket for limited pivotal movement at a point remote from the drum. The arm has a portion at the free end thereof extending between the drum and the main body of the machine, and partly into the drum. A magnetic transducer is carried on that portion of the arm adjacent to the drum. Resilient means are secured to the bracket and positioned to exert a biasing force on the arm'for urging the transducer into resilient engagement with the sound-track of a film which is being advanced over the drum.

A better understanding of the present invention may be had from the following detailed description when read in connection with the accompanying drawings, in which:

Figure 1 is a partial perspective view of a motion picture projector embodying the present invention. The exciter lamp assembly is shown opened for a better view of the sound system.

Figure 2 is a front view of a mounting means for a transducer and an operating switch therefore constructed in accordance with the present invention. The device is shown in position for operation with a film bearing an optical sound-track.

Figure 3 is similar to Figure 2 but shows the device in position for operation with a film bearing a magnetic sound track.

Figure 4 is a top view of the mounting means shown in Figures 2 and 3,

Figure 5 is an end view of the mounting means, and

Figure 6 is a side view, partly broken away, of the operating switch assembly shown in Figure 3.

Referring now to the drawings in more particularity, there is shown an embodiment of the present invention as applied to a conventional motion picture projector 2 in which a film 4 is pulled from a supply reel (not shown) by a sprocket 6 and advanced intermittently by a pulldown mechanism (not shown) through a projection gate 8, over a guide roller 10, under a pressure roller 12, around a sound drum 14, over a filter roller 16, and around a. sprocket 17 to a take-up reel (not shown).

The mounting means for the signal translating apparatus, shown more clearly in Figures 2-5, consists of a mounting bracket 18 which is secured to the frame of the machine. An aperture 20 near one end of the bracket is adapted to receive a shaft 22 upon which the sound drum 14 is carried. To the opposite end of the bracket, remote from the sound drum, there is secured a pivot pin 24. An arm 26 is mounted, at one end thereof, on the pivot pin 24.

Surrounding the pivot pin, and between that pin and the arm there is placed an eccentric sleeve 28. A pin 30 extends from the end of the eccentric sleeve into a complementary recess 32 in a knurled cap member 34. The knurled cap member is secured to the pivot pin 24 by a screw 36.

On the bottom of the bracket 18 (as viewed in Figures 2 and 3) adjacent the pivot pin 24 there is secured a folded leaf spring 38. The free end of the spring presses against an adjustable stop 40 on the arm 26. This stop may comprise, as shown, a screw 40 and a nylon unthreaded insert 42 which is pressed into a suitable opening in the arm. By varying the length of the stop, the pressure exerted thereon by the spring may be accordingly adjusted. The free end of the spring is provided with a slight twist whereby the pressure exerted on the stop 40 has a component of force in a crosswise direction to take up any play that may be introduced by the tolerances in the assembly adjacent to the pivot pin 24.

A screw 44 with an eccentric head 46 is attached to the bracket 18. The eccentric head 46 extends through an elongated opening 48 in the arm 26. The threaded portion of the screw 44 extends through a second nylon insert 50 which is securely imbedded in the bracket. The purpose served by both of the

nylon inserts

42 and 50 is to permit intentional adjustments of the respective screw members, but, because of their binding action, to prevent a misadjustmcnt from occurring through vibration of the apparatus, or the like.

The free end of the pivoted arm 26 is somewhat enlarged and is recessed on the top of the enlarged portion to contain a magnetic transducer unit 52, preferably of the type shown and claimed in a copending application to Granthan, Serial No. 102,023, filed June 29, 1949, now Patent No. 2,621,259, issued December 9, 1952. The transducer unit comprises a core assembly 54 which, with its associated coils, is molded into a block of plastic material 56. A transducer retaining spring 58 is secured to' the body of the arm and extends outwardly over an edge of the plastic portion of the transducer unit 52. A substantially inverted-U-shaped front plate 60 is secured to the face of the enlarged portion of the arm 26 by a pair of screws 62. Between the transducer unit 52 and the front plate 60 there is placed a rocker plate 64. A pair of adjusting screws 66 extend through the front plate and press the rocker plate 64 against a substantially flat face on the transducer unit, the remainder of the surface of the transducer unit, as viewed in a transverse plane being substantially circular. This arrangement provides means whereby the transducer may be adjusted for azimuth. That is, the gap in the core may be oriented at substantially 90 to the direction of travel of the sound track thereover.

The enlarged portion of the end of the arm 26 is provided with a substantially inverted-U-shaped recess in the bottom thereof. The legs of this U-shaped recess are adapted to straddle the shaft 22 of the sound drum 14. The sound drum is a hollow cylindrical drum having an open end which is open to the rear or towards the frame of the machine. The enlarged free end of the arm extends partially into the interior of the drum so that the transducer unit carried thereby is positioned with the film contacting surface of the core assembly adjacent to the rear edge of the drum. In this position the transducer is adapted to engage the sound track portion of the film which overhangs the rear edge of the drum as it is being advanced thereover.

In addition to the magnetic transducer, the pivoted arm also carries a mirror 68. This mirror is carried in a V-shaped recess in the extreme end of the arm 26, in such a position that a beam of light projected from an exciter lamp unit 70 passes through andis modulated by an optical sound track on the film being advanced around the drum. falls upon the mirror 68 and is reflected thereby to a photocell 72.

One of the legs 74 defining the U-shaped recess in the bottom of the free end of the arm is extended below the drum. There is a notch 76 provided in the side of this extended leg. In order to effect a shift from the magnetic sound system to the optical sound system or vice versa there is provided a mechanical switching arrangement. The switch mechanism includes a mounting plate 77 which is secured to the frame of the machine. Extending outwardly from the mounting plate is an operating handle or switch shaft 80, which is keyed to the knob 78, extends through a suitable bearing 82 and terminates behind the mounting plate 76 in an eccentric cam 84. The cam 84 rides in a transversely elongated opening 86 in a switch plate 88. The arrangement of the cam and the opening in the switch plate is substantially equivalent to a scotch yoke. Rotation of the cam produces a vertical (as viewed in the drawings) movement of the switch plate. An extension 90 on the switch plate terminates in a hook-like projection 92 which engages the edges of the notch 76 in the extended leg 74 of the arm 26.

A microswitch 94 is mounted on the back of the switch mounting plate 77 and adapted to be actuated by the movement of the switch plate 88 as hereinafter further explained.

When the mounting assembly is placed on a machine as shown in Figure 1, the arm extends between the drum and the body of the machine, with a portion of the free end of the arm extending intothe rear open end of the drum. In this position, the transducer is placed adjacent to the open end of the drum with its upper or film contacting surface projecting slightly beyond the outer surface of the drum.

In order to adjust the position of the transducer so that the sound track on the film will engage the transducer at the non-magnetic gap therein rather than on one of the shoulders thereof, the screw 36 is loosened, freeing the knurled cap member 34 fromthe pivot pin 24. Thus loosened. the knurled cap may be rotated about the screw 36. Since the pin 30'protruding from the end of the eccentric sleeve 28 rests in the radial recess 32 in the knurled cap, rotation of the cap will cause a corresponding movement of the sleeve about the pivot pin, causing a longitudinal movement of the arm 26 carrying the transducer. Thus the transducer may be shifted with a transverse translational movement with respect to the drum whereby the gap in the transducer may be adjusted with respect to the curvature of the film defined by the drum to produce optimum magnetic coupling between the transducer and the sound track. While the arm and the transducer have been thus adjusted, the screw may then be tightened, locking the several parts in their respective positions.

To adjust the transducer radially of the sound drum to regulate the distance that the transducer projects beyond the surface of the drum, the screw 44 with the eccentric head 46 is rotated. Since the eccentric head 46 projects through the opening 48 in the arm, and the folded leaf spring 38 presses the arm in a direction so that one side of the opening bears on the eccentric head, rotation of the screw 44 will cause a rotational movement of the arm about the pivot pin 24 commensurate with the shift in the direction of the eccentricity of the screw head. So long as the are through which the arm is thus rotated is small, the movement of the transducer occasioned thereby will be substantially radial with respect to the drum. The

extent to which the transducer projects beyond the surface of the drum, together with the adjustment of the arm with respect to the folded leaf spring, determines the pressure that the film contacting surface of the transducer will exert upon the sound-track portion of the film. The opening 48 in the arm through which the eccentric head of the screw 44 projects is elongated to accommodate the longitudinal movement of the arm as previously described. The opening is also somewhat larger, in the direction transverse of the arm, than the eccentric head of the screw. This arrangement permits a limited amount of freedom of movement of the arm against the bias pressure exerted thereon by the leaf spring. Thus, when the film is passing over the drum, the transducer is biased into a resilient engagement therewith.

If, through wear or other causes, it becomes necessary to readjust the transducer, the foregoing procedure may be repeated, obviating the necessity of remachining the parts.

When the apparatus has been set to operate with film having a magnetic sound-track, the hook-like projections 92 on the extension of the switch plate 88 projects into the notch 76 in the leg 74 of the arm 26 without engaging the edges of the notch. That is, the hook-like member rides free in the notch. Thus, the arm, and hence the transducer, is free to follow any irregularities in the film without interference from the switch portion of the assembly.

The stroke or travel of the switch plate 88 is, however, greater than the intended amount of movement of the free end of the arm. Therefore, when the selector knob is turned to the optical" position and the cam 84 causes the plate to move downward (as viewed in the drawings), the initial movement of the plate takes up the slack between the hook-like projection and the lower edge of the notch. The remainder of the downward stroke pulls the arm, against the force of the bias spring 38, to a position where the film contacting surface of the transducer is below the outer surface of the sound drum, hence out of engagement with a film being advanced over the drum.

The purpose served in moving the transducer out of engagement with film when using a film bearing an optical sound track is twofold. First, running the film over the transducer while the transducer is not being used would produce unnecessary wear on the face of the transducer. Second, in accordance with standard operating procedure, no stationary member should be allowed to engage the optical sound-track portion of a film while it is being run. This prevents scratching the film, which scratches would produce distortion in the optical reproduction of the recorded signal.

When the arm has thus been shifted by the operation of the switch mechanism, the mirror 68 carried in the recess in the end of. the arm is in a position to reflect the light from the exciter lamp assembly 70 onto the photocell unit 72. If, then, a film bearing an optical soundtrack is advanced over the sound drum, the film will pass between the exciter lamp and the mirror and thereby modulate the light beam in accordance with the signal on the optical sound-track.

The microswitch 94 mounted on the switch mounting plate is connected in series with the exciter lamp of the optical system and, in the system illustrated, should be of the type which is open when released. Thus, when the system is in position to respond to a magnetic soundtrack, the switch plate does not bear on the actuator of the switch, therefore, the eXciter lamp is not energized. However, when the system is switched to optical, the switch plate depresses the actuator of the microswitch, closing the circuit to the exciter lamp preparatory to operation with a film bearing an optical sound-track.

What is claimed is:

1. A sound reproducing unit for magnetic film records comprising a sound drum, means for advancing film over said drum, a shaft for said drum, a bracket having a portion surrounding said shaft, an arm, pivot means connecting one end of said arm to said bracket at a point remote from said drum, said arm having a portion at the other or free end thereof extending adjacent said drum, a magnetic transducer mounted on the free end of said arm adjacent to said drum whereby said transducer is adapted to engage a portion of a film being drawn over said drum, resilient means operatively coupled between said bracket and said arm for biasing said transducer into engagement with said film, and means including an eccentric member surrounding said pivot means for effecting an adjustment of said arm in a direction longitudinal thereof whereby said transducer may be adjusted with respect to the curvature of said drum.

2. The invention as set forth in claim 1 characterized by the addition of means including a second eccentric member for efiecting an adjustment of said arm in a direction transverse thereof, said second eccentric member being rotatably secured to said bracket, said arm having an elongated opening through which said eccentric member projects.

3. In sound motion picture apparatus of the type adapted for use with film bearing a magnetic sound-track, having a sound drum about which said film is adapted to be advanced and a magnetic transducer adapted to engage the magnetic sound-track on said film adjacent said drum; mounting means for said transducer comprising a bracket, an arm, pivot means connecting one end of said arm to said bracket at a point remote from said drum, said arm having a portion at the other or free end thereof extending adjacent said drum, said transducer being mounted on said arm adjacent the free end thereof, resilient means operatively coupled between said bracket and said arm for biasing said arm in a rotational direction about said pivot with respect to said bracket, an adjustable stop means for determining the position of said arm with respect to said bracket, said adjustable stop means comprising an eccentric member rotatably mounted on said bracket, said arm having an elongated opening therein through which said eccentric member projects, and means including an eccentric member surrounding said pivot means for effecting adjustment of said arm in a direction longitudinal thereof with respect to said bracket.

References Cited in the file of this patent UNITED STATES PATENTS 2,003,434 Goldhammer June 4, 1935 2,257,028 Westerkamp Sept. 23, 1941 2,439,446 Begun Apr. 13, 1948 2,535,480 Begun Dec. 26, 1950 2,550,916 Davis May 1, 1951 2,560,569 Hare June 17, 1951 2,585,913 Camras Feb. 19, 1952 2,588,616 Carlson Mar. 11, 1952 2,605,364 Masterson July 29, 1952