Dual slide projector and tray

A dual slide tray projection system is disclosed. The projector (12) has two independently operating projection mechanisms including gates (24, 26) advancing mechanisms (28, 30, 32, 34) and lens assemblies (202, 204). The slide tray (60) includes an inner (62) an outer (64) ring. The rings are independently advanceable and selectable and are only locked together by locking mechanism (140) when the tray is removed from the projector at the 0 index position.

TECHNICAL FIELD 
This invention relates generally to slide projectors and trays therefore, 
more specifically, to an improvement which permits a single slide tray 
having two concentric ringed compartments to project in independent 
sequence, slides from each tray simultaneously or alternately. 
BACKGROUND OF THE INVENTION 
Slide projectors and trays, particularly those using circular trays, are 
well known in the art. (See, for example, U.S. Pat. No. 3,499,708 and U.S. 
Pat. No. 3,411,845). In particular, the series of projectors made by Kodak 
(.TM.) in their Carousel (.TM.) line use a gravity feed system having a 
horizontally disposed circular tray to project slides (see U.S. Pat. No. 
3,276,314). 
In many applications, however, it is important to align two projectors to 
cover the same image area so that a programmable lap dissolve may be used 
to fade from one slide to the next, or simulate motion by simple animation 
or rapid slide change. These functions must necessarily be performed by 
two projectors or otherwise a projector with two projection means and 
separately addressable slide trays. One such system is that shown in U.S. 
Pat. No. 3,718,392 which employs two straight-line slide trays interlocked 
into a side-by-side relationship. This limits the unit to sequential slide 
access to slides immediately preceding and following the projected slide. 
Unfortunately, straight-line slide trays have not been convenient for 
projecting a large series of slides as the length necessary for the tray 
becomes prohibitive. Furthermore, if the dissolve programming indicates 
the need to superimpose an image over three or four other images, the 
effect has to be simulated by the use of additional slides which would use 
up more of the limited tray space. In addition, if the slides are 
projected out of sequence involving random access, a straight-line slide 
tray will have inordinately long access time where the slides have 
addresses which would be at opposite ends of the tray. 
In the present invention, functions which could be performed by two 
separate slide projectors are combined into a single unitary machine using 
a unique circular tray which can independently and randomly access any 
slide in either of its concentric slide holding rings. Combining this 
single unit projection system with a programmable lap dissolve creates an 
effective tool for communication which is as easy to use as a single 
projector. Set up time and reliability are enhanced while the size of the 
machine and slide trays are capable of being produced in a convenient size 
such that they may be easily transported. 
BRIEF SUMMARY OF THE INVENTION 
The present invention is directed to a slide projecting system including a 
projector and a slide tray with first and second concentric slide holding 
rings. Bearing means are disposed between said first and second rings to 
allow for relative rotation of the rings. Means are also provided in each 
ring for containing slides therewithin and accessing one slide in each 
ring at a time. 
According to another aspect of the invention, there is disclosed means for 
correcting for parallax between a pair of lenses. 
According to another aspect of the invention, there is disclosed a dual 
slide projection tray in accordance with the above. 
Various advantages and features of novelty which characterize the invention 
are pointed out with particularity in the claims annexed hereto and 
forming a part hereof. However, for a better understanding of the 
invention, its advantages, and objects obtained by its use, reference 
should be had to the drawings which form a further part hereof, and the 
accompanying descriptive matter in which there are illustrated and 
described a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
The preferred embodiment of the present invention employs a projection 
system based upon that found in the widely sold Kodak Carousel (.TM.) 
projector series such as models 650, 750, 800, 4000, 5600, and the like. 
Further detail of these machines is shown in U.S. Pat. No. 3,276,314 
issued to Robinson. All of the above are hereby incorporated by reference. 
To avoid an inordinately long description, the detailed description herein 
will cover only those features which either would not be apparent to a 
person skilled in the art or which are already disclosed in any of the 
above references. Furthermore, it is understood that although the 
preferred embodiment is based on the Carousel (.TM.) concept, that other 
projection systems currently known could be adapted to employ the present 
invention drawing only upon skills of an ordinary person in the art to 
achieve this transition. 
Now referring to the drawings in detail, wherein like numerals represent 
like parts, there is shown in FIG. 1, a top plan view of the dual 
projector 12 having a top surface 14, a center spindle 16, a pair of 
lenses 18 and 20, and a plurality of controls 22. 
On top surface 14, there can be seen gates 24 and 26 in the preferred 
side-by-side radially in-line arrangement. Adjacent each of the gates is 
an engagement arm 28 and 30 and the advancing arm (used for advancing and 
reversing) 32 and 34. On the other side of gates 24 and 26 are apertures 
36 and 38 which are used to supply warm air to the slide tray to provide 
focusing stability. The operation of parts 24-38 is described in U.S. Pat. 
No. 3,276,314 and is used in all Carousel (.TM.) projectors. The operation 
of the gating and advancing means will therefore not be described in 
further detail except to say that the present invention employs the same 
gating system in a side-by-side relationship. 
Spindle 16 is the same as that used in the above cited references and has a 
tab portion 40 which extends beyond the periphery of the spindle. The tab 
can be retracted by turning screw 42. The retraction permits removal of 
the slide tray (other than at notch 67) in the event it becomes jammed in 
a position other than the 0 (zero) index, as will be explained 
hereinafter. 
Adjacent gate 26 toward the outer periphery of surface 14 there is located 
a flange 44 which extends into a depressed circular region 45. A similar 
depressed circular region 46 is located concentric with region 45. These 
regions provide space for indexing pins found on the tray, as will be 
explained hereinafter. Flange 44 provides a keyway which permits insertion 
and removal of the tray only when the keyway on the tray is aligned with 
the flange (at the 0 index position). 
The top surface 14 preferably includes three pins or members projecting 
outwardly therefrom. The first pin 50 is used to engage the outer ring of 
the tray as will be explained hereinafter. The second pin 52 is used to 
engage the inner ring of the tray, and the third pin 54 is used to release 
a locking mechanism on the tray which locks the inner and outer rings 
together as will be explained hereinafter. 
Turning to the slide tray 60 itself, there is shown in FIG. 2 a top view 
and in FIG. 3 a bottom view thereof. In brief, the slide tray resembles 
that commonly employed on the Kodak Carousel (.TM.) projectors disclosed 
in the references cited above. To the extent that the tray 60 is identical 
with the prior art, such matters will not be discussed in detail. 
Tray 60, however, departs substantially from the prior art in that it is a 
dual ring slide tray and designed to perform the functions thereof. As 
seen in FIG. 2, tray 60 includes a first inner ring 62 and a second outer 
ring 64 concentric therewith. The inner diameter of ring 64 is greater 
than the outer diameter of ring 62. At the outer edge of ring 64 is a 
keyway 66 which mates with flange 44 on the projector. 
Ring 64 includes a plurality of slots or compartments 68 which are used to 
hold slides in a vertically spaced orientation. Each of the slots has an 
indexing number 70 associated therewith and located at its outer 
periphery. Slot 0 is prevented from receiving slides by a bridge 72. 
The inner ring 62 similarly is calibrated with index numbers 80 which 
correspond to slide compartments 88. Slot 0 is prevented from receiving 
slides by bridge 82. It is noted that in the preferred embodiment, an 
equal number of slide compartments are found in both rings 62 and 64. This 
was accomplished by spacing the compartments in ring 64 wider apart so 
that they will be in substantial alignment with the inner ring. This is 
done for convenience; however, it is possible to have a larger number of 
slides in the outer ring. Slides are prevented from falling out of 
compartments 68 and 88 from the top surface by a friction ring 63, 65. 
Ring 63 is well known in the art and used in the prior art Carousel (.TM.) 
slide trays. Ring 65 is similar therto except that it engages the outer 
periphery of ring 64 rather than the inner periphery. Ring 65 includes 
similar serrated portions to frictionally engage the wedge portion 69 on 
the outer periphery. 
The interconnection between rings 62 and 64 can best be seen in FIG. 4. 
Between compartments 88 and 68 there is a region which includes a 
plurality of bearing members 90 (which can also be seen in FIG. 2). These 
bearings are preferably cylindrical in shape and have an aperture along 
their longitudinal axis for the insertion of spindle 92. At the outer 
periphery of ring 62, there extends a flange 94 from which indexing teeth 
96 protrude downwardly. Flange 94 also inclues a shelf 98 and apertures 
100 for receiving spindle 92 of bearings 90. 
At the top ends of the tray, there is a bridge member 102 which is annular 
in shape as can best be seen in FIG. 2. Bridge member 102 includes a notch 
104 which engages the outer periphery, upper edge of ring 62. Bridge 102 
also includes a notch 106 which engages the inner peripheral edge of ring 
64. 
When assembled, it can be seen that by means of notches 104 and 106, and 
shelf 98, rings 62 and 64 are held coplanar such that neither ring can 
move vertically with respect to the other. On the other hand, however, 
bearings 90 permit the relative rotation between the two rings to occur. 
This allows for different slides to be selected in each of the rings 
independently of the other. 
Corresponding to teeth 96 in ring 62 are teeth 108 in ring 64. These teeth 
engage the drive mechanism of the projector in a way as known in the prior 
art in the Carousel (.TM.) system. 
Turning to the underside of the tray, which can be seen in FIG. 3, inner 
ring 62 includes an indexing plate 110 which is maintained thereon by 
screws 112 which allow the plate to rotate but maintain it in substantial 
contact with the ring. 
As seen in FIG. 3, teeth 108 are preferably wider than teeth 96 in order to 
accommodate the greater angle of rotation required to advance to the next 
slide position in the outer ring. 
Similarly, ring 64 includes a bottom index plate 114 corresponding to plate 
110 on the inner ring and being held by corresponding screws 116. 
Plate 110 is maintained in its "0" index position (i.e., the starting 
position for the slide tray) by the engagement of lever 120 in an 
indentation 122 in plate 110. FIG. 4 more clearly shows this locking 
engagement. Lever 120 has a portion 124 extending outwardly from the 
bottom surface of the slide tray 60. Lever 120 is biased downward by 
spring 126 which is maintained by cap 128. When slide tray 60 is placed 
upon the projector base 12, portion 124 contacts top surface 14, just 
outwardly of spindle 16 (see FIG. 1) and causes lever 120 to be biased 
upwardly. This causes disengagement of member 120 with indentation 122. 
As an alternate means for locking the inner slide tray, the structure known 
in the above cited art with respect to Carousel (.TM.) slide trays are 
also satisfactory. 
Turning back to FIG. 3, there can be seen on each plate 110 and 114 an 
indexing aperture 130 and 132, respectively. These apertures engage pins 
52 and 50, respectively, as found on the top surface of the projector (see 
FIG. 1). The purpose of the indexing aperture is to maintain bottom index 
plates 110 and 114 in a fixed position while the tray rotates. This will 
cause a different slide compartment to become accessible through slots 134 
and 136 in the plates. The force of gravity will then allow the slide to 
drop into the gate of the projector. 
To prevent rings 62 and 64 from rotating with respect to each other when 
the tray is removed from the projector, locking mechanism 140 is provided. 
This mechanism which is preferably affixed to plate 114 includes a lever 
142 on a pivot 144. The lever has a first end 146 and a second end 148 
which extends orthogonally from the main body of the lever toward the 
inner ring 62. The lever has a spring bias which causes end 148 to be 
biased upwardly against the bottom of tray 60. At position 0, teeth 96 are 
especially formed as shown with extenders 96A which insure engagement of 
end 148 of lever 142 with these particular teeth. This insures that the 
two trays will be in rotational synchronization at their 0 index position 
when the tray is removed from the projector. When the tray is installed on 
the projector, end 146 of lever 142 engages projection 54 on the projector 
(see FIG. 1) thereby disengaging the locking mechanism entirely. Reference 
can be had to FIG. 5 which shows the mechanism in a different view. Also 
in FIG. 5, there can be seen the individual slide compartments 68 in outer 
ring 64. Unlike the inner ring, the slide compartments are bounded by 
double walled, bridged elements 68A which compensate for the increased 
space between slide compartments resulting from the greater radius of the 
outer ring. 
Turning back to the projector itself, it is understood that problems of 
parallax would normally arise where two lenses spaced apart must focus on 
the same target point at various distances from the screen. If the images 
do not strike the target in exact alignment, simultaneous projection and 
rapid sequencing of similar slides will appear out of register. To 
compensate for this problem, it is necessary to have one of the lenses 
adjustable in a horizontal direction. FIGS. 6 and 7 disclose the preferred 
structure to accomplish this purpose. 
In FIG. 7, there can be seen two lens assemblies 202 and 204. Assembly 202 
is of the type known in the prior art such as used in Carousel (.TM.) 
projectors. The lens itself is mounted within a frame structure which 
itself is affixed to the projector. The frame structure includes apparatus 
for focusing which moves the lens in and out. The same arrangement is used 
in lens assembly 204 subject to the following changes. 
Lens assembly 204 includes a lens tube with optics 206 having a rack gear 
208 which engages a pinion gear and shaft 210 as known in the prior art. 
To cause horizontal movement, lens assembly 204 is mounted at its rear 
with two pivot pins 212 an 214 which are generally centered across the 
width of the lens assembly. At its front end, assembly 204 includes a 
threaded portion 216 which receives a threaded shaft 218. Shaft 218, 
affixed to the housing of the projector, is thereby immobilized except for 
its rotational movement. Assembly 204 is free to move on pivot pins 212 
and 214. Thus, by rotation of threaded shaft 218, movement is imparted to 
the front portion of lens assembly 204 causing the front end of the 
assembly to move in the horizontal right or left direction on pivots 212 
and 214. In operation, once the distance to the screen has been set, the 
user can project two identical slides to adjust for proper alignment. 
OPERATION OF THE INVENTION 
Preliminary consideration to operating the projector system is the loading 
of slides into slide tray 60. To accomplish this, the top locking rings 63 
and 65 (shown most clearly in FIG. 4) must be removed. This is 
accomplished by turning the locking ring so that its teeth disengage like 
teeth on the slide tray. The inner ring is substantially identical to that 
used in the prior art and the outer ring is simply a mirror image thereof. 
Slides may then be inserted into the slide compartments 68 and 88 with the 
exception of compartment 0 which is the starting position for the tray. 
The tray is then placed upon the projector such that keyway 66 of the tray 
is in alignment with flange 44 of the projector top surface. Likewise, 
notch 67 located toward the center of the tray will be aligned so that 
member 40 on the projector spindle 16 will pass therethrough. 
Once placed on the projector, the indexing apertures 130 and 132 in index 
plates 110 and 114 will engage pins 50 and 52 on the projector, thereby 
locking index plates against rotational movement. Lever 120, toward the 
center of the tray, will be biased upwards raising indentation 122 thereby 
releasing the effective mechanical brake between plate 110 and the inner 
ring 62. Likewise, locking mechanism 140 will be disengaged as has been 
explained earlier, so that inner ring 62 and outer ring 64 may rotate 
independently. 
In the manual mode, the operator may then select any location on either 
ring by depressing "select 1" or "select 2" controls 22 in a manner well 
known in the prior art devices. This will allow either tray to be rotated 
to a desired position for start. From then, controls 22 marked R and F can 
be used for forward and reverse movement of either tray independently or 
simultaneously. 
Computer control can be added to these controls to preprogram any sequence 
of slides in either ring. Thus, it is possible to project slides 
completely out of their original sequence, if desired. 
It is desirable to insert a duplicate slide as the first slide to be shown 
in order to orient lens assembly 206 to lens assembly 202. This can be 
done as explained above. When the projector is placed in the fan mode and 
a lap dissolve unit is plugged into the projector outlets, it will respond 
as two conventional projectors would respond to the same dissolve unit's 
program comments. 
The tray cannot normally be removed except in its 0 index position. If, 
however, a jam occurs, the tray can be released from the center spindle by 
rotating screw 42 which retracts element 40. This method is known in the 
prior art. 
It is understood that the inventive concept can be practiced upon 
projectors having horizontally disposed trays as shown, as well as 
vertically disposed trays as used in some prior art systems. 
Numerous characteristics and advantages of the invention have been set 
forth in the foregoing description together with details of the structure 
and function of the invention. The novel features thereof are pointed out 
in the appended claims. The disclosure, however, is illustrative only and 
changes may be made in detail, especially in matters of shape, size, 
arrangement of parts, within the principle of the invention, to the full 
extent of the broad general meaning of the terms in which the appended 
claims are expressed.