US2545941A - Actuating apparatus for sound systems - Google Patents

Description

March 20, 1951 P. H. CASE ET AL 2,545,941

ACTUATING APPARATUS FOR SOUND SYSTEMS Filed June 21, 1948 2 Sheets-Sheet 1 March 20, 1951 P. H. CASE ET AL 1 ACTUATING APPARATUS FOR sown SYSTEMS Filed June 21, 1948 2 Sheets-Sheet 2 Patented Mar. 20, 1951 ACTUATING APPARATUS FOR SOUND SYSTEMS Percival H. Case, Lawrence, Mich., and Philip L.

Karr and Henry J. Koeber, Jr., Chicago, 111., assignors to Illinois Watch Case 00., a corporation of Illinois Application June 21, 1948, Serial No. 34,194

7 Claims.

This invention relates to actuating apparatus for a sound system, and more particularly to actuating apparatus for a sound system having a radiant wave emitting member.

One feature of this invention is that it provides an improved bracket for mounting the radiant wave emitting member of a sound system; another feature of this invention is that it provides means on said bracket for maintaining said wave emitting member in operative position; another feature of this invention is that it provides a bracket having a pair of oppositely biased spring clips engaging the wave emittin member adjacent opposite ends thereof for maintaining said member straight despite changes in its length; a further feature of this invention is that said bracket is of insulating material so that it may be inserted in and removed from the sound system without shorting the electrical circuits of said system and without endangering the operator; still another feature of this invention is that the spring clips which maintain the wave emitting member straight despite changes in the length of said member are of conducting material and comprise a portion of the heating circuit for the wave emitting member, thereby providin an improved means for automatically connecting the wave emitting member into the heating circuit when the bracket on which said member is mounted is inserted into its housing, and similarly providing improved means for disconnecting the wave emitting member from the heating circuit when said bracket is removed from it housing; yet a further feature of this invention is that the bracket upon which the wave emitting member for the sound system is mounted is provided at one end with a gripping projection which extends out of the housing wherein said bracket is mounted, and the cap which closes the housing for said bracket is hollow and encloses said projection; and still another feature of this invention is that the housing for the bracket on which the wave emitting member is mounted has a socket of insulating material adapted slidably to receive the bracket, the spring clips on said brackets havin leaf portions for engaging the walls of said socket to hold said bracket frictionally therein.

Other features and advantages of this invention will be apparent from the following specification and from the drawings in which:

Fig. 1 is a side elevation of a moving picture projector having sound reproducing means and having apparatus for developing actuating waves constructed in accordance .with the invention;

Fig. 2 is an enlarged fragmentary vertical section through a portion of the projector shown in Fig. 1;

Fig. 3 is a fragmentary vertical section along the line 3-3 of Fig. 2;

Fig. 4 is a top plan View of the bracket upon which the wave emitting member is mounted; and

Fig. 5 is a side elevation of the apparatus of Fig. 4, the wave emitting member and the spring clips upon which it is mounted being shown in one position in solid lines and in another position in broken lines.

While it will be apparent to those skilled in the art that the invention disclosed in this specification is applicable to many different types of sound systems, the invention is illustrated as applied to a motion picture sound projector, and the invention will be described in connection with such a projector.

In the projector ilustrated in Fig. 1 a casing 10 carries a film feed spool l l and a film take-up spool 12 at least the take-up spool being driven in conventional manner, as by an electric motor (not shown) in the housing. A film l3 which is initially wound on the feed spool I I is transferred to the take-up spool 12 during the operation of the projector, this film passing over a sprocket M, from where it is fed past a film gate l5 which may be conventional. A projection lamp (not shown) within the casing Ill illuminates that portion of the film which is opposite the aperture in the gate [5, and a lens arrangement I6 is adapted to focus the beam of light on a screen.

As is well understood in the art, means are provided for causin the film to move intermittently past the gate so that each frame is stationary during the time that light from the projection lamp is thrown upon it. This means is illustrated as comprising a claw El driven in conventional manner by a cam arrangement [8. After leaving the ate 15 the film passes over a roller i9 being held in frictional contact with said roller by a lever arm 20 which carries a supplemental roller 26a. A sound drum 2| carries the now continuously moving film past the sound take-off apparatus, and the film then moves over another roller 22, over a take-up sprocket 23, and onto the take-up spool l2. The general operation of the apparatus just described is conventional and will not be described in greater detail here.

As is conventional the film l3 carries (usually along one edge) a sound track 1311, and a source of actuating waves are provided, these waves being modulated by the sound track and reproduced in any conventional manner, as for example by an amplifier and speaker arrangement associated with the projector. In a projector being built and incorporating the inventions here being claimed, the audio variations taken from the sound track are caused to modulate radio frequencies and these are transmitted to a separate amplifying and reproducing system, as for example that of a conventional radio receiver.

In a conventional sound projector provided with a source of radiant energy on one side of the sound track and a translating device, as for example a photo-electric cell, on'the other side of the sound track, the Waves from the source are modulated by the sound track on the film and the modulated waves are picked up by the photo-electric cell and converted into electrical energy which is then amplified and translated into sound. In the past it has been the usual practice to utilize an incandescent exciter lamp as the radiant source of actuating waves. The use of such an exciter lamp resulted in certain serious problems, and in the application of Philip L. Kari for Actuating Apparatus for Sound Systems filed March 5, 1948, as Serial No. 13,245, an improved means for developing the actuating waves was disclosed and claimed. This improved means is illustrated in Figs. 2 and 3 of the drawings, and will be described briefly here.

If a conventional incandescent exciter lamp is used to provide the actuating waves, and if the exciter lamp is energized from a source of varying current, as for example a conventional 60 cycle alternating current source (which is usually desirable since the film is usually driven by an A. C. motor) the temperature of the exciter lamp filament is constantly being increased or decreased at the rate of 120 cycles per second. While the filament may retain enough brightness that this change is not noticeable to the eye, actually the intensity of the illumination emitted by the exciter lamp varies at a frequency of 120 cycles per second in an amount of the order of which in effect modulates the actuating waves emitted by the lamp with a 120 cycle signal so that a corresponding hum, sometimes termed a 60 cycle hum by virtue of the frequency of the current causing it, is present in the sound output. While it is possible to minimize or eliminate this 60 cycle hum by means of providing a separate oscillator for energizing the exciter lamp filament with an alternating current having a high rate of change above the range of audibility, by employin sharply tuned rejection circuits, or by providing a separate D. C. source, as for example a battery, to energize the lamp, each of these methods of minimizing hum requires the addition of expensive and bulky apparatus to the projector.

The apparatus illustrated in Figs. 2 and 3 provides an extremely effective and simple way to eliminate hum from the sound output, and in addition this apparatus provides a source of actuating waves which is considerably less complex sitive pickup extends Within the sound drum 2| so that a portion of the device is adjacent the sound track Isa on the film 53. The photosensitive device 25 preferably comprises a lead sulphide cell which is extremely sensitive to waves in the infra-red portion of the spectrum, this type of cell being of the order of 20 or 30 times more sensitive to these waves than the cesium cell usually used for sound reproduction in the motion picture field. This sensitivity to relatively low frequencies provides advantages as will hereafter appear.

A lens 2'! is mounted in a bracket 28 within the casing 25, this bracket bein yieldable to permit slight movements of the lens as a function of the position of a focusing screw 28a. The lens may comprise merely a small cylindrical glass rod, preferably having a diameter of about of an inch.

At the end of the casing 2% remote from the sound drum there is a housing 29 having an opening which is closed by a threaded cap 30, and instead of an incandescent exciter lamp a straight filamentary type radiant wave emitting member Si is provided, this wave emitting member being illustrated as a segment of Nichrome resistance wire about one-half inch lon and having a diameter of about .012 inch.

This wave emitting member is connected in series with an impedance already in the system, as for example, the projection lamp, in order to limit the current flow through the valve emitting member which has a relatively small resistance, usually less than one ohm. The wave emitting member is heated only to a radiant temperature, as for example a temperature of the order of 1500-l800 F. so that it is characterized by a dull red or orange-red glow. When heated to such a temperature the wave emitting member emits waves in the relatively narrow infra-red and red wave band comprising only a small portion of the radiant energy frequency range near the lower end of said radiant energy frequency range. This band comprises frequencies having their energy content almost entirely in wave lengths of the order of 8,000 angstrom units and over, and cover the relatively long wave length visible waves and the even longer wavelength infra-red waves. Changes in the intensity of these waves as the result of temperature change in the filamentary wave emitting member is only very small when compared to changes in intensity in the relatively short, yellow, blue and white waves emitted by a conventional incandescent exciter lamp. Consequently the wave emitting member may be energized directly from the 60 cycle commercial alternating current which energizes the drive motor of the projector, and the small variations in intensity of the emitted waves due to the cyclical temperature changes in the member 3! are so small that hum in the sound output is substantially entirely eliminated. Therefore, there is no need .for converting the energizing current for the wave emitting member to a frequency above the audible range, for attempting to filter out the undesired waves, or for energizing the wave emitting memher from a separate D. C. source.

Furthermore, the wave emitting member may be operated in open air and need not be encased in a glass envelope or other protective device. As an additional advantage, since the Waves emitted are substantially entirely within a narrow band and are not spread out over the entire radiant spectrum avery sharp image of the straightwave emitting member may be formed on the film without using a complex and expensive optical system, the lens 21 of Figs. 2 and 3 simply comprise a commercially obtainable glass rod having a diameter of /8 of an inch. If the Waves emitted by the member 3| covered the entire radiant energy spectrum such a simple lens as that shown at 21 could not focus waves from the entire spectrum to produce an image of the sharpness required in such a projector, and a more expensive and more complex lens system would have to be used.

The present invention comprises a novel arrangement for mounting the wave emitting member 3| so that it is easily placed in operating position in the projector and is readily removable therefrom and does not buckle as its length changes when it is heated. The member 3| is secured at its opposite ends to a pair of spring clips 32 which are carried on a mounting bracket 33. The spring clips 32 are oppositely biased so that they exert a force away from each other and act to maintain the wave emitting member 3| taut and straight despite changes in the length of said member due to temperature changes as said member is heated to provide wave emission. A pair of terminals 35 are on the bracket 33, these terminals comprising the upper portions of rivets which secure the spring clips 32 to the bracket so that each terminal extends through the bracket on its under side and makes contact with the respective one of a complementary pair of terminals 36. Consequently, when the bracket 33 is mounted in operating position the wave emitting member 3| is automatically connected into its operating circuit by means of leads 31 which connect the terminals 36 with the operating circuit. The clips 32 are of conducting material, and since said'clips are in series with the terminals 36 and the wave emitting member 3|, the clips comprise a portion of the heating circuit for the filamentary wave emitting member 3|. The bracket 33 is of insulating material so that it may be placed into the housing or removed from the housing without shorting the filamentary heating circuit and without endangering the operator.

A pair of shoulders 40 and 4| within the housing 29 provide a seat for an insulating socket 42 which mount the terminals 36 and which is formed to provide a trackway in which the bracket 33 is slidable. Leaves 32a extending from the spring clips 32 engage the walls of the socket member 42, thus frictionally holding the bracket within said socket, providing good contact between the terminals 35 and 36, and preventing undesired movement or vibration of the bracket 33.

The bracket 33 has a gripping projection 33a which, as may best be seen in Fig. 3 extends out of the housing 29 when the bracket is mounted in operative position. The provision of this extension makes it easy to insert the bracket in the housing and remove it when desired without coming into contact with the wave emitting member 3| which may be hot, and without using any tools. The opening through which the bracket enters the housing is threaded as may be seen in Fig. 3 at 43, and the cap 30 has complementary threads and may be screwed onto the casing to close this opening. The cap is hollow so that it encloses the projection 33a. If desired the cap may be provided with a screw slot 30a. to facilitate its removal (see Fig. 1).

In operating a film projector or other sound system having a radiant wave emitting member of the type shown here, the member is mounted, as by welding, between the spring clips 32, these clips being compressed as shown in broken lines in Fig. 5 so that they exert a force away from each other and hold the wave emitting member taut and straight even though the length of said member increases upon temperature change as shown in full lines in said figure. The cap 30 is then unscrewed to open the housing 23 and the bracket 33 is slid into the socket 42, the leaves 320. pressing the contacts 35 down against the contacts 36 and insuring that good electrical contact will be made while at the same time the bracket 33 is frictionally held against vibration in the socket. The cap 3|) is then replaced and the wave emitting member is ready for operation. In the event it is desired to remove the wave emitting member for any reason, either during the operation of the projector when said member is heated or when the projector is not operating it is merely necessary to unscrew the cap 30, grip the projection 33a and pull the bracket out of the housing. The heating circuit to the wave emitting member will automatically be broken and at the same time there is no possibility of shorting the circuit and no danger that the operator will touch the hot member 3| While removing the bracket.

While we have shown and described certain embodiments of our invention it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

We claim:

1. In a projector having sound reproducing means, apparatus for developing actuating Waves, comprising: a straight, filamentary type radiant wave emitting member; a bracket having said member fixedly mounted thereon; a pair of oppositely biased spring clips on said bracket engaging said member adjacent opposite ends for maintaining said member straight despite changes in its length; and a housing adapted slidably to receive said bracket and member, said housing having electric terminals for energizing said wave emitting member.

2. Apparatus of the character claimed in claim 1, wherein said bracket is of insulating material and said clips are of conducting material and comprise a portion of the heating circuit for said filamentary member, said clips having terminals which slidably contact the termnals in said housing.

3. In a projector having sound reproducing means, apparatus for developing actuating waves, comprising: a wave emitting member; a bracket for mounting said member, said bracket having a gripping projection at one end; and a housing adapted slidably to receive said bracket and member, said projection extending out of said housing when said bracket is mounted in operating position for readily removing the bracket from the housing.

4. In a projector having sound reproducing means, apparatus for developing actuating waves, comprising: a wave emitting member; a bracket of insulating material for mounting said member, said bracket having a gripping projection at one end; a housing adapted slidably to receive said bracket, said projection extending out of said housing when said bracket is mounted in operating position; and a removable cap for closing said housing, the cap being removable without disturbing the bracket in the housing.

5. In a projector having sound reproducing means, apparatus for developing actuating waves, comprising: a radiant wave emitting member; a bracket of insulating material for mounting said member, said bracket having a gripping projection at one end; a spring on said bracket for maintaining said member straight despite changes in its length; a housing adapted slidably to receive said bracket, said hous n having a threaded opening and said projection extending out of said opening when said bracket is mounted in operating position; and a hollow cap adapted to be threaded on said housing to close said opening, said projection being enclosed within said hollow cap.

6. In a projector having sound reproducing means, apparatus for developing actuating waves, comprising: a, straight, filamentary type radiant wave emitting member; a bracket of insulating material for mounting said member; a pair of oppositely biased spring clips engaging said member adjacent opposite ends for maintaining said member straight despite changes in its length, said clips being of conducting material and comprising a portion of the heating circuit for said filamentary member; a housing in said projector; a socket of insulating material in said housing, said socket being adapted slidably to receive said bracket and said clips having leaf portions for engaging the Walls of said socket to hold said bracket frictionally therein; and a cap for closing said housing.

7. Apparatus of the character claimed in claim 6, wherein said bracket has a gripping projection at one end which extends out of said housing and said cap is hollow and encloses said projection.

PERCIVAL H. CASE.

PHILIP L. KARR.

HENRY J. KOEBER, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,989,836 Whitman Feb. 5, 1935 2,027,191 Morrissey Jan. 7, 1936 2,123,871 Weiss July 19, 1938 2,247,076 Arey June 24, 1941 2,300,809 Reeves Nov. 3, 1942 FOREIGN PATENTS Number Country Date 361,555 Great Britain Nov. 26, 1931

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