US3732000A

US3732000A - Sound-slide projector

Info

Publication number: US3732000A
Application number: US00239460A
Authority: US
Inventors: L Annett; G Wallin
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1972-03-30
Filing date: 1972-03-30
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08
Also published as: JPS4910033A; CA979691A

Abstract

A sound-slide projector for use with a sound-slide, wherein the sound media is a thin, flexible disk having a magnetizable coating on one face which disk is supported at a central opening therethrough on the sound-slide frame for rotation about the photographic slide and wherein a tapered capstan and a pressure roller are provided to drive the disk between their peripheries while a magnetic transducer is moved radially with respect to the disk.

Description

D United States Patet L 1 [111 3373mm Annett et al. 51 ay 8, 1973 [54] SOUND-SLIDE PROJECTOR 3,357,302 12/1967 Gerry [75] Inventors: Leland W. Annett, Crystal; George wam", Paul, both of Miml- 2,740,633 4/1956 Moore ..274/11 R [73] Assignee: Minnesota Mining & Manufacturing Company, Saint Paul, Mi Primary ExammerLeonard Forman 1 Assistant Exami'nerA. J. Mirabito Flledl 30, 1972 AttornyKinney, Alexander, Sell, Steldt & Delahunt [21] Appl. No: 239,460

[57] ABSTRACT A sound-slide ro'ector for use with a sound-slide 52 U.S.Cl. .353 19 353 120,226 184 p J E 1 Int Cl G0/3b 3 g 00% [00 wherein the sound media is a thm, flexible disk having Field 353/l5 19 a magnetizable coating on one face which disk is sup- 39 g i ported at a central opening therethrough on the sound-slide frame for rotation about the photographic slide and wherein a tapered capstan and a pressure [56] References Cited roller are provided to drive the disk between their UNTTED STATES PATENTS peripheries while a magnetic transducer is moved radially with respect to the disk. 3,245,312 4/1966 Paull .l ..353/19 3,159,078 12/1964 Schwartz ..353/19 7 Claims, 7 Drawing Figures SOUND-SLIDE PROJECTOR FIELD OF THE INVENTION The present invention relates to a sound-slide projector for projecting an image from a transparency and simultaneously recording or reproducing an audible signal and in one aspect to a projector wherein the recording medium is driven during recording and reproduction.

BACKGROUND OF THE INVENTION The prior art is replete with sound-slide projectors which utilize a sound-slide with a single frame supporting a slide transparency and a recording media. Many of the recently patented sound-slides provide the recording media with a spiral recording track. The recording media may remain stationary during a recording and/or reproduction as illustrated in U. S. Pat. Nos. 3,122,053 and 3,504,967. The first of these patents illustrates that if the sound-slide is so constructed the transducer in the machine must be made to rotate about the center of the recording media while at the same time moving radially inward thereof. Such construction is necessarily complex because of the required movement of the transducer and the necessity of having electrical connections between the rotating transducer and the stationary portion of the machine.

The recording media may also be provided in the form of a disk and supported by the sound-slide frame for rotation about its axis whereby the transducer and the sound-slide projector need only be supported for movement radially inward by the recording disk as the disk is rotated. Such sound-slides and machines for use therewith are disclosed in U. S. Pat. Nos. 3,159,078; 3,245,312; and 3,296,925. The first of these suggests driving the recording disk either by a spindle through its center or at its periphery, while the latter two patents disclose driving of the disk by a cylindrical drive roller against one face with a directly opposed cylindrical backup roller engaging the opposite face of the disk to press the disk against the drive roller. In each of these patents the disk is rigid and of substantial construction to permit driving of the disk in the disclosed mode. However, such construction of the disk substantially adds to the bulk and weight of the soundslide and thereby substantially detracts from the convenience of handling and storage as is desired especially as the number required for a single presentation or the number in a library increases.

SUMMARY OF THE INVENTION The present invention provides a sound-slide projector for use with a sound-slide wherein the sound is recorded on and/or reproduced from a thin, flexible disk having a magnetizable coating on one face, which disk is supported on the sound-slide frame at a central opening therethrough for rotation about a transparency supported for projection centrally of the sound-slide frame. The projector has a projection position from which the image on a photographic slide supported by a sound slide frame may be projected, means for moving the sound-slide frame into the projection position, a transducer supported for movement against the sound disk and means for rotating the sound disk at a constant angular velocity. The means for rotating the sound disk comprises a truncated cone shaped capstan and a pressure roller supported for engagement of the sound disk between their peripheries with the axis of the capstan intersecting the axis of the positioned sound disk at the center of the sound disk. The sound-slide projector of the present invention for the first time permits the use of a thin, flexible sound disk to keep the bulk and weight of the sound-slide to a bare minimum while avoiding the complexity of requiring the transducer in the machine to rotate with respect to the sound media.

DESCRIPTION OF THE DRAWINGS In the drawing:

FIG. 1 is a perspective view showing the front, top and one side of a sound-slide projector constructed in accordance with the present invention and a slide tray for use therewith; I

FIG. 2 is a top view partially in section of the projector and slide tray;

3 FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken generally along line 4l--4 of FIG. 2;

FIG. 5 is a top view of a portion of the projector also shown in FIG. 4;

FIG. 6 is a front elevation view of a sound-slide for use with the projector of the present invention; and

FIG. 7 is a cross-sectional view taken along line 7 7 of FIG. 6.

The sound-slide projector of the present invention has an exterior casing 10 which is formed with a channel 12 extending parallel to the optical axis of the projector. The channel 112 is formed to receive and support a slide tray 14 and it has a slide receiving slot to midway of one vertical wall to align one at a time with transverse sound-slide receptacles in the slide tray 14. The slide tray E4 is formed with gear teeth 18 along one edge wall to mesh with the teeth of a gear 19 in the machine for stepwise advancement of the slide tray 14 to align successive sound-slide receptacles therein with the slide receiving slot to in the machine. The same edge wall of the slide tray 14 is also formed with rectangular openings 20 through which a slide pusher bar 22 aligned with the slide receiving slot R6 may enter an aligned slide receptacle to push the sound-slide therein into the slide receiving slot to in the machine.

The slide pusher bar 22 is secured to a handle 23 which is accessible at the exterior of the projector casing 10 for manual manipulation. A cylindrical rod 24 is secured to the lower portion of the handle 23 and extends parallel to the pusher bar 22 across the base of the projectorand at its end it is turned upward to form a slide return arm 25 opposed to and spaced from the slide pusher bar 22.

The slide receiving slot 116 provides communication between the channel 12 and a projection position whereat a sound-slide 26 (see FIG. 6) having a frame 27 which supports a transparency 2% and a sound disk 29 is positioned with the center of the photographic transparency 28 aligned with the optical axis of the projector. The sound-slide projection position is defined at the back by a vertical wall 32 formed with an aperture 33 through which light from a lamp 34 may pass to project the image on a projection positioned transparency 28. The top of the projection position is defined by a guide bar 36 which is formed with a lip to overhang the front face of a sound-slide frame 27 (see FIGS. 3 and 4) while the base is defined by a spaced pair of

feet

38 and 39 which are slightly inclined upwardly from the vertical wall 32 to bias :1 sound-slide frame 27 against the vertical wall. The extent of removal of the sound-slide frame 27 from the slide tray 14 when completely in projection position is determined by slide stop arm 41 that is pivoted on the vertical wall 32 and a stationary stop stud 42 which limits pivotal movement of the arm 41. In the projection position the sound-slide frame 27 is not completely removed from the slide tray 14 (see FIG. 3) so that when engaged by the slide return arm 25 it will be aligned with and smoothly slide back into its proper receptacle in the slide tray 14.

The sound-slide frame 27 comprises a rigid plastic frame formed with a central aperture 35 to expose the transparency 28 for projection and a rectangular recess 37 centrally of one edge to expose both faces of the sound disk 29 for driving thereof. The transparency 28 is mounted in a cardboard frame, as is common, which frame is supported by the sound-slide frame 27 to center the transparency in the central aperture 35. The sound disk 29 comprises a thin, flexible base material having a magnetizable coating on one face. In the illustrated embodiment the base material is a 3-mil thick polyester film. The sound disk 29 is formed with a central aperture larger than that through the sound-slide frame 27 and is retained on the frame for free rotation on a cylindrical bearing surface 30 that is concentric with the sound-slide frame aperture. A raised spiral transducer guide track 31 is defined on the magnetizable face of the sound disk 29.

A capstan 45 and a pressure roller 47' are supported adjacent the slide projection position to engage the exposed portion of a sound disk 29 of a projection positioned sound-slide 26 between their peripheries.

The capstan 45 has a truncated cone shape and is carried by a flywheel 49 which is continuously driven by a motor 50 through a belt drive (not shown) when the projector is in use. The flywheel 49 is supported for free rotation and inclined to the base of the projector casing to position the capstan 45 with its line of contact with the sound disk 29 vertically oriented and its axis passing through the center of the projection positioned sound disk. The capstan 45 is formed of a rigid material to impart a uniform drive speed to the sound disk 29. Because of its truncated conical shape and because its axis intersects the axis of the sound disk at the center of the sound disk the capstan 45 imparts a constant angular velocity to the sound disk independent of the different radii at which it contacts the sound disk. Therefore, it produces no force on the sound disk 29 which would pull the sound disk against the bearing surface 30 of the sound-slide frame 27 and tend to distort or tear the thin, flexible sound disk 29 as would a cylindrical capstan.

The pressure roller 47 is supported adjacent one end of a support and camming arm 52 that is pivoted about a vertical axis on a stud 53 at its opposite end. The pressure roller is formed of a resilient material and has the shape of two coaxial truncated conical sections 55 and S6. The difference in radii and the juncture of the smaller portion 55 and the larger portion 56 is made equal to the thickness of the sound disk 29.

The pressure roller 47 is supported fir free rotation on a standoff piece 58 secured to the support arm 52 and having an inclined upper surface to bring the smaller diameter portion 55 of the pressure roller into line contact with the sound disk 29 and the larger diameter portion 56 into line contact with the capstan 45 beyond the periphery of the sound disk 29. When the capstan 45 and the pressure roller 47 are in driving contact (see FIG. 4) the axis of the pressure roller 47 is oriented to intersect the axis of the sound disk 29 and the axis of the capstan 45 at the center of the sound disk 29. In this manner there is no opportunity for even the pressure roller to exert a force on the sound disk 29 which would pull it against the bearing surface 30 on the sound-slide frame 27. However, within the scope of the present invention, the capstan 45 and the pressure roller 47 may be adjusted a small amount radially of a projection positioned sound disk 29 to adjust the driving speed imparted to the sound disk 29 so long as the intersection of the axis of the capstan 45 and the axis of the pressure roller 47 is not moved a substantial distance away from the center of the sound disk 29.

A helical spring 60 attached to the end of the pressure roller support arm 52 farthest removed from its pivot 53 normally biases the support arm 52 to resiliently engage the pressure roller 47 against the capstan 45. At the same end, a camming arm 61 is pivoted on the lower face of the pressure roller support arm 52 and extends therefrom into engagement with the cylindrical slide return rod 24. At its engagement with the slide return rod 24 the camming arm 61 is formed with an upstanding cylinder which contacts the slide return rod 24 and a smaller diameter guide cylinder 62 which extends upward and contacts a guide surface 63 along the edge of the pressure roller support arm 52, which guide surface limits the pivotal movement of the camming arm 61 to an are providing two over center positions for the camming arm 61. The slide return rod 24 is formed with a recess 65 to engage the end of the camming arm 61. The relationship between the camming arm 61 and the slide return rod 24 is such that when a sound-slide is fully moved into projection position the pressure roller 47 is resiliently engaged against the capstan 45 by the spring 60. As movement of the slide return rod 24 is started to remove the sound-slide from projection position the camming arm 61 engaged by the return rod recess 65 immediately beings to pivot and moves the pressure roller support arm 52 and the pressure roller 47 away from the capstan 45 to disengage from the sound disk 29. Further movement of the slide return rod 24 moves the camming arm 61 to its over center position where its movement is stopped by the end of the guide surface 63 with the pressure roller 47 disengaged from the capstan 45. Continued movement of the slide return rod 24 then further forces the camming arm 61 outward and causes further separation between the pressure roller and the capstan. When a sound-slide 26 is moved into projection position the opposite sequence occurs and as the sound-slide reaches the projection position the camming arm 61 returns to its over center position illustrated in FIG. 5 and the pressure roller is again moved into resilient engagement with the capstan 45.

A magnetic transducer 68 is supported for movement radially with respect to a projection positioned sound disk 29 at one end of a support arm 70 and it includes a follower 69 which projects outward to follow the spiral transducer guide track 31 on a sound disk 29. The transducer support arm 79 is pivoted about its opposite end on a pin 7B that extends from the vertical wall 32. It is formed with an inclined cam face 72 facing away from the transducer 68 and extending around the pivot pin 71. The direction of inclination being aligned with the length of the transducer support arm 70. A helical compression spring 74 is retained between the cam face 72 and a washer 75 secured to the end of the pivot pin 71 and surrounds the pivot pin. The compression spring 74 exerts an uneven force on the cam face 72 because of the cam face inclination, biasing the transducer support arm 70 to pivot about an axis perpendicular to the axis of the pivot pin 'ill and also perpendicular to the length of the transducer support arm 70. The transducer support arm is formed with an oblong opening at the pivot pin 71 to permit limited pivotal movement about the perpendicular axis so that the compression spring 7 may resiliently bias the transducer 68 into engagement with the sound disk 29.

A switching arm 77 depends from the transducer support arm 70 and it carries an adjustment screw at the end thereof to close a pair of electrical contacts 80 and 81 to signal when the transducer 68 approaches the end of the spiral guide track 31 on the sound disk 29 for a purpose which will be hereinafter described. An adjustable stop 83 depending from the vertical wall 32 into the pivotal path of the transducer support arm 70 defines the start or home position for the transducer 68 and a light helical return spring 84 extending between the free end of the transducer support arm 70 and a bracket also supporting the stop 83 provides positive return of the transducer 68 to its home position after disengagement of the transducer follower 69 from the spiral guide track 31 on a sound disk 29.

Disengagement of the transducer 68 from the spiral sound track 31 on the sound disk 29 is provided by a lever arm 86 which is pivoted on a stud 97 between its ends, one end carrying a cylindrical bushing 88 which engages a cam surface 89 at the end of the cylindrical slide return rod 24 and the opposite end engaging an upturned flange of a slide bar 91. The upturned flange of the slide bar 911 is also engaged by an adjustment screw 92 carried by an extension of the transducer support arm 70. A heavier tension spring 94 biases the lever arm 86 against the slide bar 91 to move the transducer support arm 70 and the and the transducer 69 away from the sound disk 29. With the sound-slide 26 in the projection position the cam surface 89 at the end of the slide return rod 24 prevents the spring 9d from pivoting the lever arm 86. At the same time a lighter tension spring 95 urges the slide bar 91 against the end of the lever arm 86 and the compression spring 79 resiliently biases the transducer 69 into engagement with the sound disk 29. However, at the start of movement of the slide return rod 2d to move the sound-slide 26 out of projection position the cam surface 99 moves to permit the lever arm 86 to pivot under the force of spring 94 pushing slide bar 91 along its guides and, in turn, pivoting the transducer support arm 79 away from the sound disk 29. The transducer support arm 70 is then biased to its home position by return spring 84 to await movement against and following of the spiral guide track on another sound disk.

Closing of

electrical contacts

89 and 81 by the switching arm 77 at the end of the recording track on the sound disk 29 actuates a solenoid 98 to begin automatic return of the projection positioned sound-slide 26, advancement of the slide tray l4 and movement of a successive sound-slide into projection position. This automatic function is primarily accomplished by a hooked link 199 which is pivoted on the slide return rod 24 at one end and pivoted and slidable on the bushing 101 at its opposite end. The hooked link 100 is reciprocated by a cylindrical projection 1041 that is secured adjacent the periphery of a gear 103.

Actuation of the solenoid 98 pivots a spring biased stop link 196 about its remote end pivot point to permit a carrier link 198 to be pivoted about a point spaced from its ends to carry an idler roller 199 into engagement with the capstan flywheel 49. Through a reduction gear train the idler roller 109 then drives the gear 103 in a counterclockwise direction. The cylindrical projection 194 pushes the hooked link 1190 first outward to carry the projectionv positioned sound-slide back into its receptacle in the slide tray 14', through an intermediate link (not shown) the slide tray gear 19 and the slide tray 14 are then advanced one receptacle, and finally the projection 194i engages the hook in the link 1199 to move the successive sound-slide into projection position. As the gear 193 returns to its original position the stop link 106 is biased to its original position and engages and returns the carrier link 108 to its original position thereby disengaging the idler roller 199 from the flywheel 49 and removing the drive to gear 103.

A switch (not shown) is positioned to be opened by a sound-slide moved into projection position, which switch if not opened actuates the solenoid 98. Thus, if there is no sound-slide in the aligned slide tray receptacle the automatic function will continue to search until a sound-slide is found.

In use, the machine is placed in the on mode to illuminate the lamp 3d and to supply power to the motor 59 to continuously drive the capstan 45. A slide tray 14 is inserted into the channel 112 from the rear and slid toward the front of the machine. To align the first receptacle in the slide tray M with the slide receiving slot 16 it is necessary to manually move the slide changer handle 23 outward from the casing 19 and the to advance the slide tray to properly align the first receptacle with the slide pusher bar 22 adjacent the opening 29 therefore in one edge wall of the tray and the slide receiving slot 16 adjacent the opening in the receptacle through which the sound-slide therein may be removed. The slide return handle 23 is then moved manually toward the casing l0 causing the pusher bar 22 to eater the receptacle in a slide tray lid and to push the sound-slide 26 therein into projection position.

As the sound-slide 26 reaches the projection position the pressure roller carnming arm 6i moves with the slide return rod 2% permitting the spring 60 to bias the pressure roller 47 to engage the pressure roller with the capstan 45 and the sound disk 29 to rotate the sound disk about its axis. At the same time the camming surface 89 at the end of the slide return rod 24 engages the lever arm 96 permitting the tension spring 95 to move the slide bar 91 away from the transducer support arm and thereby to permit the compression spring 74 to bias the transducer support arm 79 to resiliently engage the transducer 69 with the sound disk 29.

The capstan 45 and the pressure roller 47 then rotate the sound disk 29 at a uniform angular velocity as the follower 69 on the transducer 68 is guided by the spiral guide track 31 on the sound disk 29 to record or reproduce information about the transparency 28 then being projected. As the transducer 68 reaches the end of the sound track on the sound disk 29 the adjustment screw 78 on the switching arm 77 closes electrical contacts 80 and 81 to actuate the solenoid 98.

Actuation of the solenoid 98 causes the idler roller 109 to be engaged to drive gear 103 in a counterclockwise direction. The cylindrical projection 104 on gear 103 is then carried into engagement with the hooked link 100 to being slide return movement of the slide return rod 24.

At the outset of slide return movement of the slide rod 24, the cam surface 89 at the end of the slide rod 24 moves to permit the lever arm 86 to be biased by tension spring 94 to move the slide bar 91 and thereby to pivot the transducer support arm 70 to disengage the transducer 68 from the sound disk 29. The transducer support arm 70 is thereafter biased by its return spring 84 to return it to its home position against stop 83. Simultaneously, camming arm 61 is moved with the recess 65 in the slide return rod 24 and cams the pressure roller support arm 52 and the pressure roller 47 away from the sound disk 29 and the capstan 45 to completely disengage the drive from the sound disk 29.

Continued rotation of the gear 103 causes the slide return arm 25 to engage the sound-slide 26 in projection position and to return it completely to its receptacle in the slide tray 14. The slide tray 14 is then moved by gear 19 stepwise one sound-slide receptacle to align the second receptacle with the slide receiving slot 16. Finally, rotation of the gear 103 causes its cylindrical projection 104 to engage the hook in link 100 to engage the slide pusher bar 22 with the sound-slide in the second receptacle in the slide tray 14 and to move it into projection position. As the second sound-slide reaches the projection position the drive to the gear 103 is interrupted, the pressure roller support arm 52 is biased to engage the pressure roller 47 and the capstan 45 with the sound disk 29 and the transducer support arm 70 is biased to engage the transducer 68 with the sound disk 29 as aforedescribed. The transparency 28 of the second sound-slide 26 is then projected and information with respect thereto is required on or reproduced from the sound disk 29.

In like manner each sound-slide in the slide tray 14 may be moved automatically into the slide projection position, the transparency thereof being projected while the information with respect thereto is recorded on or reproduced from its sound disk and the soundslide 26 is finally returned to the slide tray 14.

lclaim:

I. In a sound-slide projector for use with a soundslide wherein the transparency is supported for projection of the image thereon centrally of the sound-slide frame and the sound is to be recorded on and/or reproduced from a thin, flexible disk having a magnetizable coating on one face, which disk has a central opening and is supported on the sound-slide frame for rotation about the transparency, the improvement comprising:

means defining a projection position from which the image on a transparency supported by a said sound-slide frame may be projected,

means for moving a said sound-slide frame into said projection position, a transducer, means supporting said transducer for movement against a said sound disk supported by a said sound-slide frame in said projection position, and

means for rotating said projection positioned sounddisk at a constant angular velocity, said means for rotating comprising a truncated cone shaped capstan and a pressure roller supported for engagement of the sound disk between their peripheries with the axis of said capstan intersecting the axis of the positioned sound disk at the center of the sound disk.

2. The sound-slide projector of claim 1 wherein said pressure roller has a right conical section shape and is positioned with its axis intersecting the axis of said capstan and the axis of the positioned sound disk at the center of the sound disk.

3. The sound-slide projector of claim 2 wherein said pressure roller is formed with two coaxial right conical sections which at their juncture have a difference in radii equal to the thickness of a said sound disk, said pressure roller being supported to position the smaller section thereof to contact and press the positioned sound disk against said capstan and to position the larger section thereof to contact said capstan beyond the periphery of the positioned sound disk.

4. The sound-slide projector of claim 1 including means defining a channel extending parallel to the projection axis of said projector for supporting a tray having a plurality of sound-slide receptacles; and, means defining a sound-slide receiving slot communicating with said channel and said projection position to be aligned with successive sound-slides in successive receptacles in a said tray supported in said channel as the tray is step-wise advanced, said channel and the projection axis of said projector being spaced such that said sound-slide projection position extends into said channel; and wherein said means for moving a said sound-slide frame includes means for moving a soundslide in a said slide tray receptacle aligned with said guide slot into said projection position with a portion of its frame remaining in its receptacle in the tray.

5. The sound-slide projector of claim 4 wherein said means for moving a sound-slide includes means for completely returning a said sound-slide to its receptacle in the tray and including cam means responsive to said means for moving a sound-slide for camming said transducer and said pressure roller away from a said sound-slide simultaneously prior to movement of the sound-slide from said projection position to its receptacle in the tray.

6. The sound-slide projector of claim 1 wherein said means supporting said transducer supports said transducer for movement radially with respect to said sound disk supported by a said sound-slide frame in said projection position.

7. The sound-slide projector of claim 6 wherein said means supporting said transducer comprises an elongated transducer support arm pivoted on a pin extending parallel to the projection axis of said sound-slide projector, said arm being formed with a cam face extending partially around its pivot on said pin and inclined to the axis of said pin, which cam face is engaged by a helical spring supported coaxially with said sound disk.

Claims

1. In a sound-slide projector for use with a sound-slide wherein the transparency is supported for projection of the image thereon centrally of the sound-slide frame and the sound is to be recorded on and/or reproduced from a thin, flexible disk having a magnetizable coating on one face, which disk has a central opening and is supported on the sound-slide frame for rotation about the transparency, the improvement comprising: means defining a projection position from which the image on a transparency supported by a said sound-slide frame may be projected, means for moving a said sound-slide frame into said projection position, a transducer, means supporting said transducer for movement against a said sound disk supported by a said sound-slide frame in said projection position, and means for rotating said projection positioned sound-disk at a constant angular velocity, said means for rotating comprising a truncated cone shaped capstan and a pressure roller supported for engagement of the sound disk between their peripheries with the axis of said capstan intersecting the axis of the positioned sound disk at the center of the sound disk.

4. The sound-slide projector of claim 1 including means defining a channel extending parallel to the projection axis of said projector for supporting a tray having a plurality of sound-slide receptacles; and, means defining a sound-slide receiving slot communicating with said channel and said projection position to be aligned with successive sound-slides in successive receptacles in a said tray supported in said channel as the tray is step-wise advanced, said channel and the projection axis of said projector being spaced such that said sound-slide projection position extends into said channel; and wherein said means for moving a said sound-slide frame includes means for moving a sound-slide in a said slide tray receptacle aligned with said guide slot into said projection position with a portion of its frame remaining in its receptacle in the tray.

7. The sound-slide projector of claim 6 wherein said means supporting said transducer comprises an elongated transducer support arm pivoted on a pin extending parallel to the projection axis of said sound-slide projector, Said arm being formed with a cam face extending partially around its pivot on said pin and inclined to the axis of said pin, which cam face is engaged by a helical spring supported coaxially with said pin to bias said arm to resiliently urge said transducer into engagement with a said projection positioned sound disk.