United States Patent Bennett  RANDOM SELECTION SYSTEM FOR A SLIDE PROJECTOR 72 inventor: Frank P. Bennett, Northbrook, 111.
 Assignee: GAF Corporation, New York, NY.
 Filed: June 24, 1968  Appl. No.2 739,353
 u.s.c1. ..3s3/2s,31s/67s,318/685, 353/103 [511 1111.01. .0031 23/06  FieldoiSearch ..3s3/2s,1o3,1o4,107,10s, 353/111, 112, 114, 115, 116, 117, 118-, 318/42, 43, 20.810, 20.860, 675
 References Clted UNITED STATES PATENTS 1,292,768 1/1919 Harle ..318/43X Feb. 22, 1972 3,296,727 1/1967 Liguori ..353/117 X Primary Examiner-Leonard Forman Assistant Examiner-Steven L. Stephan Attorney-McDouga1l, Hersh & Scot ABSTRACT The random selection system consists of an attachment unit which is detachably mounted on the housing of the slide projector, a remote control unit which is separate and remote from the slide projector, and an extension cable connecting these units. The attachment unit contains a commutator. The remote control unit includes receiving means in the form of DC motor parts. The commutator acts as a transmitter and the motor parts as a receiver for stepping or rotating the rotor in synchronization with rotation of the movable component of the commutator. The rotor drives a seeking contact for movement in an arcuate path.
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PATENTEDFEB22 I972 SHEET 11 HF 11 A INVENTOR FRANK F? BENNET RANDOM SELECTION SYSTEM FOR A SLIDE PROJECTOR OBJECTS OF THE INVENTION A primary object of the present invention is the provision of a new and improved random selection system for a slide projector, wherein such system is of simplified and low-cost construction.
Another primary object of the present invention is the provision of a random selection system for a slide projector, which system utilizes transmitting and receiving means which in a preferred form consist of a DC stepping motor with a remote commutator.
Another object of the present invention is the provision of a random selection system of the type described, which system has a so-called short-way home" feature, i.e., in the case of a circular slide tray for example, the tray is rotated automatically in a direction resulting in the minimum amount of rotational movement in presenting the selected slide adjacent the slide projection gate of the projector.
Still another object of the present invention is the provision of a random selection system of the type described, which system includes simplified selector means adapting the system for alternately accommodating two types of slide trays, these trays differing in the number of slide-receiving spaces they contain.
Another object of the present invention is the provision of a random selection system for a slide projector, which system does not require major changesor alterations to the associated slide projector.
Still another object of the present invention is the provision of a random selection system of the type described, which system includes a control box remote from the projector and including means for selecting any one of the slide-receiving spaces in the slide tray as well as including means for advancing or reversing the slide tray one slide-receiving space at a time.
These and other objects and advantages of the invention will become apparent from the following specification disclosing a preferred embodiment shown in the accompanying drawings.
DESCRIPTION OF THE DRAWINGS FIG. 1 is perspective view of the components constituting the random selection system according to the present invention showing the same associated with a slide projector;
FIG. 2 is an enlarged view of the remote control unit with the housing thereof removed for purposes of illustrating the interior components;
FIG. 3 is a view similar to FIG. 2 showing the remote unit with the initiate button" removed and also showing an indicator masking plate in a position different from that shown in FIG. 2;
FIG. 4 is a section taken generally along the line 4-4 of FIG. 3 with certain parts being removed;
FIG. 5 is a top plan view of a rotatable selector disk having two dial scales, one for a l-slide" tray and the other for an 80-slide" tray;
FIG. 6 is a perspective view of the other side of the disk shown in FIG. and primarily showing the means constituting arcuate contact strips;
FIG. 7 is a perspective view of the remote control housing with the cover thereof removed, this view primarily showing the l00-slide contact gear and the 80-slide contact gear;
FIG. 8 is a view of the l00-slide and 80-slide gear in assembled relation;
FIG. 9 is a perspective view of the 80-slide contact gear only;
FIG. 10 is a perspective view of the 100-slide gear;
FIG. 11 is a perspective view of the other side ofthe 80-slide gear;
FIG. 12 is a perspective view of the remote control unit with the housing and many parts removed and primarily showing a central bearing column having a plurality of electrical slip rings thereon;
FIG. 13 is a fragmentary section taken along the line 13-13 of FIG. 2;
FIG. 13A (adjacent FIG. 5) is a fragmentary view taken along line 13A'13A of FIG. 13;
FIG. 14 is an enlarged view of the attachment unit taken along the line 14-14 of FIG. 1 showing this unit with the housing removed;
FIG. 15 is a top plan view of the attachment unit as seen in FIG. 14;
FIG. 16 is a view taken along the line 16-16 of FIG. 1 showing the attachment unit with its housing removed;
FIG. 17 is a perspective view similar to FIG. 16;
FIG. 18 is a perspective showing the bottom of the attachment unit and the side thereof shown in FIG. 16;
FIG. 19 is a view taken along the line 19l9 of FIG. 14;
FIG. 20 is an electrical schematic of the random selection system;
FIG. 21 is an electrical schematic of the DC stepping motor and remote commutator therefor;
FIG. 22 is a perspective view of the rotor of the DC stepping motor;
FIG, 23 is an enlarged, fragmentary, top plan view ofa 100- slide tray;
FIG. 24 is an enlarged plan view of the teeth on such tray;
FIG. 25 is a top plan view of the tray drive gear; and
FIG. 26 is an enlarged, fragmentary, top view of the teeth on an -slide tray.
DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the random selection system according to the present invention includes a remote control unit 10 and an attachment unit 12, the latter being detachably mounted on a slide projector 14. The remote control unit 10 and the attachment unit 12 are connected together by a multiconductor extension cable 15. Preferably, at least one end of this cable is connected to a multiterminal jack (not shown) for detachable engagement with either the unit 10 or the unit 12 to facilitate storage of these units when not in use.
The embodiment of the invention disclosed herein as been designed for use with the slide projector disclosed in the application of Walter J. Hall, Ser. No. 684,202, filed Nov. 20, 1967, now US. Pat. No. 3,499,708. It will be apparent to those skilled in the art that the present invention can be readily adapted for use in association with other types and forms of slide projectors, and therefore the present invention is not to be limited for use only with the projector shown in the aforementioned Hall application. I
The remote control unit 10 includes a housing definedby a rectangular base 16 and a shell-piece 17. The unit 10 includes a slide selector knob 18 having an initiate button" 20 mounted centrally thereof. This unit also includes a so-called one-slide advance button 21 and a one-slide reverse button" 22. A 80-100 selector arm 24 is mounted on this unit. The top wall of the shell 17 has an aperture therein defining a window preferably containing a transparent plate 25 having a reference line or mark 26 thereon.
Referring particularly to FIGS. 2, 3, 5 and 6, the remote control unit 10 includes a rotatably mounted disk, generally designated 28, which disk has an integral hub portion 29 (which defines the knob 18) on one face thereof, this face bearing a first dial scale 30 and an 80 dial scale 31. Mounted within the hub are two pairs of diodes 33 and 34. Also mounted within the hub 29 is a metal bracket 35 having a pair of brush arms or contacts 35a, this bracket being secured to the disk 28, (which is formed of dielectric material) by a fastener 36. A similar metal bracket 38 includes a pair of brush arms or contacts 38a, this bracket being secured to the disk 28 by a fastener 39. It will be understood the brush arms 35a and 38a are vertically spaced from each other and therefore electrically insulated from each other in all relative positions. As noted in FIG. 5, the disk 28 includes a central bore As noted in FIG. 3, a fixed contact button 42 is mounted on a small disk 43, the latter being suitably mounted within the hub 29 in vertical spaced relation with the bore 40. The disk 43 mounts a spring arm or movable contact 44 which is normally in spaced relation with the contact button 42, the former being adapted to be engaged by the initiate button 20 for closing the contacts 42, 44 when such button is depressed.
The other face of the disk 28 is illustrated in FIG. 6. This face mounts a first annular series ofdetents 46 defining a socalled 100-slide" wheel and a second annular series of detents 47 defining a so-called 80-slide wheel. Mounted within these formations is a first pair of arcuate contact strips 49 and 50, adjacent ends of these strips being in spaced relation and forming dielectric areas 51 and 52. The lower face of the disk 28 also mounts an annular contact ring 53 and a further arcuate contact ring 54. It will be understood that all contact rings or strips are electrically insulated from each other.
The brush arms 35a are electrically connected with the an nular contact strip 53 by means of the fastener 36; in like manner, the brush arms 38a are electrically connected with the arcuate contact strip 54 by means of the fastener 39. The diodes 34 connect annular contact member 53 with arcuate contact strips 49 and 50; the diodes 33 connect the arcuate strip 54 with the contact strips 49 and 50. As will be explained below in connection with the description of the electrical schematic, the arrangement of the diodes is such that contact strips 49 and 50 are provided respectively with positive and negative DC voltage.
The disk 28 is rotatably mounted on a central post 56 (FIGS. 7 and 12), which post includes four contact rings 57, 58, 59 and 60 electrically and physically separated by intermediate dielectric bands, It will be understood that when the disk 28 is mounted in place on the post 56, the contact wipers 35a wipe or engage the ring 57 and the wipers 38a wipe or engage the ring 58.
Rotatably mounted on the post 56 just below the disk 28 is a so-called l-slide gear 62 (FIGS. 8 and having a series of teeth 63. The gear 62 includes a central, circular opening 64 defining its bearing surface. This gear also contains a generally U-shaped cutout including legs 65, 66 which communicate with the opening 64. An inverted U-shaped metal contact bracket 68 is mounted on the gear 62 (which is formed of dielectric material) by fasteners 69, the ends of this bracket being received in the cutout portions 65 and 66. The bracket 68 includes an integral arm 70 mounting a seeking contact 71 at the end thereof. As noted in FIG. 8, the bracket 68 includes an integral pair of contact arms 68a.
Rotatably mounted on the post 56 below the gear 62 for rotation independently thereof is a so-called 80-slide gear 74 having an annular series of gear teeth 75. The gear 74 is dished out and includes an integral, upstanding hub formation 76 which mounts a contact ring 78. The upper end of the formation 76 also mounts an arcuate contact strip 79 by means of fasteners 80. Strip 79 includes an integral arm 81 mounting at the outer end thereof a seeking contact 82. Mounted on the strip 79 is another contact strip which includes a pair of contact wiper arms 79a, which arms are in wiping engagement with the ring 59 on the post 56. It will be understood the bracket 79 and the various contacts thereon are all in insulated spaced relation from the contact ring 78.
The gear 74 includes a central bore 84 which extendsthrough the hub formation 76. The underside of the gear 74 (FIG. 11) supports a contact bracket 85 by means of a fastener 86. This bracket includes integral contact arms or wipers 85a which wipe or engage the contact ring 60 on the post-56. A conductor wire 87 defines an electrical connection between the ring 78 and the contact bracket 85. When the gear 62 and 74 are mounted on the post 56, the contact wipers 68a engage the contact ring 78 thereby establishing an electrical path between the contact ring 60 and the seeking contact 71. It will be readily apparent that a current path is established between the ring 59 and the seeking contact 82.
The post 56 is suitably mounted centrally of a dished-out member 89 (FIG. 12) which member is in turn supported on a plate 90. The member 89 has an annular rim 89a which engages the underside of the gear 74 and thereby rotatably supports the latter. The gear 62 is rotatably supported by engagement of its bearing surface 64 with the hub formation 76 on the gear 74. I I
The plate 90 is mounted in vertical spaced relation from the base 16 by a plurality of posts 91. This plate mounts a bracket 93 which in turn mounts a gear 94 integral with a pinion gear 95. As noted in FIG. 7, the pinion gear 95 meshes with the teeth 63 and 75 on the gears 62 and 74, respectively. As will be explained more fully hereinbelow, the gear 62 includes a greater number of teeth 63 than the number of teeth 75 on the gear 74. Accordingly, the pinion gear 74 which is rotated at a constant rate, will drive the gear 74 at a greater velocity or annular rate than the gear 62. Gear 94 meshes with a gear 96 which is mounted on the output shaft of a DC stepping motor 97, the latter being suitably mounted between the base 16 and the plate 90.
Turning now particularly to FIGS. 7 and 12, it will be noted that the selector switch member 24 is integral with a bar 99, the latter being suitably mounted on the plate 90 for reciprocal sliding movement. The bar 99 includes a notch 100 in the underside thereof which receives the operating member or button 101 of a two-position switch (not shown) which is of conventional construction. The end of bar 99 remote from the member 24 mounts an integral bracket 102 having an aperture 103 and a horizontally disposed leg 104.
Referring to FIGS. 2 and 3, the aperture 103 in the bracket portion 102 rockably mounts a swivel member 105, the latter being in abutting relation with one end of a coil spring 106. The coil spring encircles a stem member 108 which is integral with a hemispherical formation 190. It will be understood the formation 109 and its stem 108 are movable relative to the swivel 105, the spring 106 serving to urge these members apart.
The hemispherical formation 109 is rockably received in an aperture 110 (FIG. 4) defined in a tab integral with a detent actuator 112. This actuator is pivotally mounted about a pin 113, the latter being mounted from a block 114 which is in turn suitably supported on the plate 90. The block 114 includes bores 115 and 116 respectively mounting a pair of detent balls (not shown) positioned for being alternately biased into engagement with the detent formations 46 and 47 on the disk 28. The actuator 112 includes generally oppositely disposed arms 117 and 118 having formations (not shown) on their distal ends for engagement of the detent balls.
' The leg 104 on the bracket 102 which is integral with the bar 99 pivotally mounts one end of an arm 120, the other end of this arm being pivotally mounted to an intermediate portion of an arm 121. One end of the arm 121 is pivotally mounted from a post 122 (FIGS. 7 and 12) suitably supported from the plate 90. The other end of the arm 121 is pivotally connected to a masking plate 123 which is arcuate in shape and adapted alternately to mask portions of the dial scales 30 and 31. The masking plate includes an integral leg portion 124 the distal end of which is pivotally mounted to one end of an arm 125; the other end of this arm is pivotally mounted from a post 126. It should be apparent that shifting movement of the bar 99, which is brought about by manual actuation of the arm 24, results in swinging the masking plate 123 back and forth between the positions shownin FIGS. 2 and 3. It should also be apparent that this shifting movement of the bar 99 will serve to rock the detent actuator 112 for alternately detentin g the detent formations 46 and 47 on the disk 28.
When the selector arm 24 is moved to the 100-s1ide position, the switch actuator 101 is positioned for establishing the appropriate circuitry (which will be explained hereinbelow), the masking plate 123 is positioned for obscuring a portion of the 80-slide dial 31 and the actuator 112 is rocked for biasing one of the detent balls into engagement with the detent formations 46. The detent ball will be yieldably engaged with these detent formations by the action of the spring 106. When the selector 24 is moved to the 80-slide position, the switch actuator 101 is moved to its other position, the masking plate 103 1 then obscures a portion'of the IOU-slide indicator dial 30, and
the other detent ball is yieldably urged intoengagement with the detent formations 47.
The disk 28 is preferably formed of translucent material. A diffuser plate 128 (FIGS. 2 and 3) is mounted beneath the disk 28 in alignment with the window 25 formed in the housing shell 17, this diffuser plate being mounted on a post 129 in turn supported from the plate 90. A bulb 130 is mounted beneath this diffuser plate, a suitable opening being provided in the plate 90 to accommodate the bulb. The bulb is received in a conventional socket 132 supported from a bar 133 extending from the lower end of the post 129. It will be apparent the bulb 130 serves to illuminate the portion of the disk 28 which is visible through the window 25.
Turning to FIGS. 7, 12 and 13, the advance button" 21 is of stepped cylindrical construction and is mounted for vertical reciprocal movement in a split cylindrical formation 136 supported on the plate 90. The lower end of the button 21 is of bifurcated construction for receiving one end of an actuator plate 137, the latter having an inclined cam surface 138. The actuator plate is mounted in a slot 90a in the plate 90 for horizontal reciprocal sliding movement relative thereto. It will be understood the button 21 includes an inclined cam surface (not shown) for complementary engagement with the cam surface 138 thereby causing the actuator 137 to be slid inwardly of the plate 90 when the button21 is depressed.
The actuator 137 has an upstanding portion 139 mounting a pair of detent fingers 140 and 141 for respective engagement with detent formations 46 and 47. The actuator 137 has the inner end thereof supporting a dowel (not shown) received in one end of a spring 143 (FIG. 13). This end of the actuator 137 carries a sleeve 144 for confining a portion of the spring 143. As also noted in FIG. 13, the actuator 137 has a depending portion 145 mounting a fastener 145a for actuating engagement with a contact strip 146, the latter having a plate portion 146a secured to the underside of plate 90 by a fastener 147.
The reverse button 22 is identical with the button 21 and is associated with an actuator 149 identical with the actuator 137 and in opposite hand relation therewith. The actuator 149 supports detent fingers 150 and 151 and for engagement with detent formations 46 and 47, respectively. This actuator carries a dowel 153 which is received in the other end of the spring 143. A depending portion 154 of the actuator mounts a fastener 154a arranged for actuating engagement with a contact strip 155. A plate 155a integral with this contact strip is secured to the underside of the plate 90 by a fastener 157.
It will be apparent the spring 143 acts to urge the actuators 137, 149 apart for normally holding the buttons 21 and 22 in their uppermost positions. When the button 21 is depressed, the fingers 140, 141 are brought into engagement with respective detent formations 46 and 47 for detenting the disk 28 through an increment determined by which of the formations 46 and 47 is being engaged by the above-mentioned detent ball. When the reverse button 22 is depressed, the disk is detented in an opposite direction. When either of the buttons 21 or 22 are depressed, the contacts 146, 155 are closed.
As noted in FIGS. 1 and 14 through 19, the attachment unit 12 includes a housing shell enclosing framework primarily consisting of upper and lower frame plates 159 and 160, respectively, held in parallel-spaced relation by a plurality of posts 161. This framework mounts a small, reversible-drive motor 162 which is of conventional design and includes an output shaft 163 mounting a gear 164. A gear reduction system is defined by a gear 165 being integral with another gear 166 both mounted for rotation about a pin 167 supported from the frame plate 159. The gear 166 meshes with an intermediate gear 168 which is rotatably mounted on a pin 169 also supported from the frame plate 159. Gear 168 is integral with a smaller gear 170 which meshes with a larger gear 172 fixed to the upper end ofa commutator shaft 173.
It will be apparent that energization of the motor 162 will cause rotation to the commutator shaft 173. Preferably, a suitable slip drive connection (not shown) is provided to prevent damage to the aforedescribed gear train in the event of a jam anywhere in the mechanism.
The commutator shaft 173 has an enlarged central portion supporting a first contact ring defined by three separate segments 175a 175b, and 1750 (FIG. 21) which are electrically insulated from each other. The commutator also includes three continuous contact rings 176, 177 and 178; it will be understood these three rings are respectively connected to the segments 175a through 175a by suitable connections within the interior of the commutator shaft.
Mounted between the frame plates 159 and 160 is a pair of brush bars 180 and 181 (FIGS. 14, 16 and 17). These brush bars mount a first pair of brushes 182, 183 in l80 oppositely disposed relation for wiping engagement with the segments 175a through 175C. The brush mounting bars 180, 181 mount second, third and fourth pairs of brushes 185, 186 and 187 which are in respective wiping engagement with the rings 176, 177 and 178 on the commutator.
The commutator shaft 173 carries a gear 189 (FIG. 16) adjacent the lower end thereof, this gear being in meshing engagement with a larger diameter gear 190 mounted on a subshaft 191. Opposite ends of this subshaft are suitably journaled in the frame plates 159, 160. The upper end of the subshaft 191 carries a gear 192 in meshing engagement with a gear 193 mounted on a drive shaft 195. This drive shaft is connected to the gear 194 by means of a spline connection (not shown) permitting the shaft 195 to be slid back and forth between upper and lower positions and at the same time maintaining its driven relationship with the gear 194.
The drive shaft 195 mounts a drive gear 196 at the lower end thereof, the teeth of this gear being adapted for meshing engagement with the teeth 197 (FIG. 1) formed around the lower periphery of a circular slide tray 198. A button 199 is mounted on the upper end of the shaft 195 to provide a convenient means for raising and lowering this shaft to engage and disengage the drive gear 196 from the teeth 197 of the circular slide tray.
As will be explained more fully below, the slide tray 198 shown for purposes of illustration has 100 slide-receiving spaces and an equal number of teeth 197. An 80-slide circular slide tray (not shown) has 80 peripherially disposed teeth for engagement by the gear 196. The teeth on the gear 196 and the teeth on both of the trays are configured as explained below such that rotation of the gear 196 through an arc defined by 360 divided by the number of teeth on this gear the slide tray 198 will be rotated through 3.6" and the 80-slide tray will be rotated through 4.5.
Means are provided for locking and unlocking the gear 196, such means including a pair of locking pawls 201 (FIGS. 18 and 19) which are pivotally mounted about corresponding ends thereof on a pair of pins 202, the other ends of the pawls being adapted for locking engagement with the teeth on the gear 196 as seen in FIG. 19. The pawls include first integral arms 203 which are apertured for receiving opposite ends of a bowed spring 204, the latter serving to urge the pawls to the locked position. The pawls 201 include integral, second arms 205 arranged to be simultaneously engaged by a tab 206 formed on one end of a bellcrank member 208, the latter being pivoted about one of the pins 202. The other end of the bell crank is pivotally engaged with one end of a push wire 290; the other end of this wire is pivotally connected to one end of a bellcrank 210 pivoted about a pin 211. The other end of this bellcrank is pivotally engaged with a U-shaped bracket 212 mounted on the operating member 213 ofa solenoid 214. By reference to FIGS. 18 and 19, it should be apparent that when this solenoid is energized, the pawls 201 are disengaged from the teeth of gear 196 thereby permitting free rotation thereof and that when the solenoid is deenergized the bowed spring 204 acts to snap the pawls 201 into locking engagement with the teeth on the drive gear.
Referring to FIGS. 14 and 17, a solenoid 216 has the actuating member thereof connected to a disk 217 for rotating the same in a counterclockwise direction as seen in FIG. 14. This disk carries a pin (not shown) which extends through a slot 219 in an actuating plate 220, the lower end of which plate is received in a slot 221 (FIG. 18) thereby mounting the plate 220 for vertical reciprocal movement. The upper end of the plate 220 has a bent-over tab 222 which is apertured for receiving a load pin 224, opposite ends of the latter being received in appropriate fittings or bushings mounted in the frame plates 159, 160 thereby mounting the pin 224 for vertical reciprocal movement. A coil spring 225 encircles a portion of the pin 224; the upper end of this spring abuts the underside of the tab 222. The other end of this spring abuts a washer 226 which is suitably connected to the pin 224. It will be understood that when the solenoid 216 is energized the disk 217 is rotated for lowering the pin 224 to the lowermost position thereof which is illustrated in FIG. 14. When the solenoid is deenergized, a spring 228 serves to return the pin 224 to its uppermost position. One end of this spring is connected in a suitable aperture in the frame plate 159; its other end is connected to one end of a link 229, the other end of which link is connected to the pin (not shown) carried by the disk 217.
The framework within the attachment unit 12 also supports, by suitable bracket means, a transformer 230 and a pair of relays 231, 232. The purpose and function of these components will be explained below in connection with the description of the electrical schematic.
Turning to FIGS. 21 and 22, the motor 97, which is of the DC stepping type, includes permanent magnet field pieces 235, 236 of north-south polarity, respectively, and a rotor 237 having three coil windings with the windings 2370, 237b and 2370 connected with slip rings 238-240 as shown. These slip rings, which are mounted on the shaft of the rotor as noted in FIG. 22, are wiped by suitable brushes 241-243 schematically illustrated in FIG. 21. The brushes 241-243 are connected by the conductors 244-246 to respectivepairs of brushes 185 through 187. The rings 176-178 on the commutator shaft 173 are respectively connected to contact segments 175a, 175b and 1750 by the conductors 248-250. It will be understood these connections are actually formed within the interior of the commutator shaft 173. The brushes 182, 183, which engage only two of the segments 175a through 1750 at any one time, are provided with DC current through the lines 252, 253.
What has just been described is essentially a DC stepping motor with a remote commutator. The commutator, consisting of the rings 175-178 and the brushes 182-187 constitute a transmitter and the motor parts consisting of the pole pieces 235, 236 and the rotor 237 constit ute a receiver. The rotor 237 will step or rotate in synchronization with rotation of the commutator shaft 173 by reason of signals generated by the transmitter, such signals being in response to rotation of the shaft 173.
The brushes 182, 183, which are provided with a source of direct current voltage, always engage two of the commutator segments 175a through 1750. When direct current is applied to any two of the segments 17511-1750, one coil of the rotor 237 will be connected across such rings and the two remaining rotor coils which are in series will be connected across the same two contact segments. The magnetic field established by such energization rotates the rotor in conformance with known magnetic principles. In the particular arrangement illustrated in FIG. 21, the coil 237a is energized in such a way that the magnetic flux developed has the south pole at the top of this coil which is thereby attracted to the permanent north pole piece 235. The other two coils 23717 and 2370 are energized such that the magnetic flux developed has the north magnetic pole at the outer extremities of these two rotor coils thereby causing them to be attracted to the south magnetic pole piece 236. Therefore, the rotor 237 is rotated to and held in the position illustrated so long as the brushes 182, 183 engage the contact segments 175a, 175b.
As the contact segments 1750 through 1750 rotate, it will be apparent that another combination between the brushes 182, 183 and the segments a-175c will be formed affecting corresponding but different combinations of energization in the rotor coils for stepping or rotating the rotor 237 to a subsequent position. It will be apparent that in the embodiment shown for purposes of illustration, six possible combinations of energization andconsequent magnetic polarity will result during one complete rotation of the commutator shaft 173. In other words, for each one-sixth of an increment of rotation of the transmitter or commutator shaft 173, the receiver or rotor 237 will respond in one-sixth turn increments in synchronization therewith.
The DC stepping motor with remote commutator as just described is not of course to be limited to the particular form illustrated and disclosed herein. Many variations are possible. For example, the permanent magnet field structure illustrated may have substituted therefor an electromagnetic field of well known and conventional configuration. The receiver or rotor is not of course to be limited to three-pole construction, as it could, for example, be of five-pole construction. Also, the rotor may be a permanent magnet and the field defined by wound construction.
It will be apparent to those skilled in the art that the energy required in the receiver is not reflected as a load on the transmitter or commutator. The total energy absorption in the transmitter-commutator is the mechanical input required to rotate the shaft 173. It will therefore be appreciated the receiver or rotor can be quite delicate and responsive to very low level signal inputs. It will also be appreciated that the power or torque capable of being generated by the rotor 237 is a function of the physical and electrical structure together with the amount of power switched to the rotor by the transmitter-commutator. Accordingly, it will be understood that from very low input a considerable amount of usable work can be obtained from the receiver or rotor 237. Therefore, the DC stepping motor with remote commutator described herein provides not only a device wherein one rotatable element will follow directions from a remotely disposed rotatable element, but also provides a device useful as a power amplifier as well.
The DC motor with remote commutator arrangement shown provides for absolute synchronization between the transmitter and receiver so long as the receiver is not loaded beyond its designed torque capabilities. It will be apparent that the rotor 237 can be rotated in either direction in response to corresponding direction of rotation of the commutator shaft 173.
Referring to FIG. 20, the various components of the random selection system of the present invention which have not been mentioned above will now be described. The relay 231 controls three sets of switches consisting of movable contacts 255a, 256a, 257a and pairs of fixed contacts 255b, 2550, 256 b, 2560, 257b, 2570. The movable contacts are biased to the positions illustrated; when the relay 231 is energized, the movable contacts are simultaneously moved to their other positions.
The relay 232 actuates a pair of switches consisting of movable contacts 258a, 259a, and associated pairs of fixed contacts 258b, 2580,259b, 2590. The movable contacts of these switches are biased to the position illustrated. Energizing of the relay 232 results in movement of the movable contacts to their other position.
The system is energized from conventional line voltage of approximately 1 15 volts, this line voltage being represented by the conductors 261, 262. In the embodiment according to the present invention, line voltage is obtained from a suitable plug (not shown) on the slide projector 14. The housing 158 of the attachment unit 12 is preferably provided with a pair of contact prongs (not shown) which are received in a plug on the slide projector when the unit 12 is mounted thereon.
As explained fully in the aforementioned Hall application, the projector includes a so-called half-cycle park switch which is represented herein by a movable contact 263a associated with a fixed pair of contacts 263b, 2630. When the slide-changing mechanism in the projector 14 positions a slide in the projection gate, the half-cycle part switch is in the condition shown in FIG. 20. When the slide-changing mechanism has removed a slide from the gate and returned the same to the tray but has not yet positioned the next slide in the gate, i.e., when the slide-changing mechanism has moved through only one half of a cycle, the movable contact 263a is forced into engagement with the fixed contact 2630.
A load or actuating button is indicated at 264. As explained in the Hall application, operation-of this button restores a slide in the projection gate to its space in the tray.
The line 252 providing DC voltage to the stepping motor is connected between a pair of oppositely poled diodes 265 which are connected to the low-voltage side of the transformer 230. It will be noted that the line 253 is connected to a center tap on the low-voltage side of the transformer through the switch 258.
Lines 230a, 23Gb extend from the low-voltage side of the transformer and are connected to respective slip rings 57 and 58 on the post 56. It will be noted these two lines serve to energize the bulb 130. Another line 230C extends from the center tap on the low-voltage side of the transformer and connects to a dead contact in the remote control unit 10. This dead contact may be used in conjunction with another contact to energize an indicator bulb (not shown) during the period of time between selection of a slide and arrival of such slide at the projection gate.
A voltage control network for the motor 162 is provided in the form of four diodes 266 connected in a bridge formation in shunt relation with the motor, this bridge arrangement having a diagonal connection including four diodes 267. This control network is independent of line voltage variations over a range considerably greater than the expected variations from line voltage. This control is required to maintain strict synchronization between the transmitter and receiver under opposite, extreme conditions, such as the occurrence of highline voltage at a time when the slide tray is unloaded, and the occurrence of line voltage less than usual at a time when the tray is heavily loaded. The voltage control system just described controls motor speed within very narrow limits for maintaining precise synchronization under these two diverse conditions.
The operation of the random selection system according to the present invention is as follows.
Assume that the circular slide tray 198 is fully loaded with slides and operatively positioned on the slide projector 14. Assume further that the unit 12 is attached to the projector and that the button 199 (FIG. 1) is depressed for bringing the drive gear 196 into meshing engagement with the teeth 197 on the slide tray. Preferably, the shaft 195 which rotates the drive gear is provided with an extension (not shown) on its lower end for actuating the disabling switch" described in the above-mentioned Hall application. Actuation of this disabling switch serves to interrupt the control circuit which causes rotation of the tray 198 when the random selection system is not being used.
Since the tray 198 contains 100 slide-receiving spaces, the switch actuator 24 will be in the 100-slide position serving to locate the switch actuator 101 in the condition illustrated in FIG. 20. Assume also that a slide is being projected in the projection gate. Under this condition, the solenoids 214, 216, the relays 231, 232 and the drive motor 162 will be deenergized. The stepping motor 97 will likewise be deenergized and the 100-slide seeking contact 71 will be located in the dielectric area 51 between the arcuate contact strips 49 and 50. Under these conditions, all of the various switches will be in the condition shown in FIG. 20.
Now assume that the operator rotates the selector knob 18 in a clockwise direction (with reference to FIG. for locating the selected slide number on the scale 30 (FIG. 5) beneath the mark 26 (FIG. 1) on the window 25. This action causes movement of the disk 28 for placing the plus" contact strip 49 into engagement with the seeking contact 71. Now, the initiate button 20 is depressed for closing the switch contacts 42. 44 thereby completing a circuit through the relay 231 and solenoid 214. Energization of the relay 231 causes the contacts 255a, 256a, 2570 to be brought into engagement with respective contacts 2550, 256e, 2570. Since the contacts 255a, 2550 are in parallel with the contacts 42, 44, the relay 231 and solenoid 214 will remain energized after release of the initiate button 20. Energization of the solenoid 214 actuates the lock pawls 201 for unlocking or releasing the drive gear 196. It will be noted that under these conditions, the drive motor 162 will not be energized as thesame is shunted through the contacts 259a, 259b.
Engagement of contacts 256a, 2560 results in energization of the solenoid 216. This causes the pin 224 to be lowered thereby depressing the load button 264 on the slide projector 14. This actuation of the load button causes the slide-changing mechanism in the projector to commence a cycle of operation. After the slide-changing mechanism has moved through a half cycle thereby removing a slide from the projection gate and returning the same to its space in the slide tray, the slidechanging mechanism is stopped by movement of the half-cycle switch contact 263a into engagement with the fixed contact 2630. This will result in energization of the relay 232 which causes the movable contacts 258a, 259a to be brought into engagement with the fixed contacts 258e, 2590. Movement of the contact 259a into engagement with the contact 259C removes the shunt across the motor 162 thereby causing the same to be energized to commence rotation of the slide tray. The engagement between the contacts 258a, 2580 provides power to the stepping motor and commutator through the low-voltage side of the transformer 230.
As the motor 162 rotates for driving the slide tray, this motor also rotates the commutator shaft 173 which, as previously explained, acts as a transmitter sending signals to the rotor 237 in the motor 97 whereby the latter is rotated or stepped in synchronization with rotation of the shaft 173. This results in driving of the seeking contact 71 which will be in wiping engagement with the arcuate strip 49,
When the seeking contact 71 reaches the dielectric area 51, the circuit is opened and relay 231, solenoid 214 and the drive motor 162 are immediately deenergized. Movement of contact 257a into engagement with contact 257b results in a dynamic breaking influence on the motor 162 by virtue of short-circuiting the back EMF of the motor. Mechanical restraint to rotation of the tray is also brought about as deenergization of the solenoid 214 causes the locking pawls 201 to come into locking engagement with the drive gear 196. The various parts are of course arranged and adapted such that the selected slide-receiving space in the tray will be precisely positioned adjacent the projection gate when seeking contact 71 reaches dielectric area 51.
Solenoid 216 is also deenergized when the seeking contact 71 reaches the dielectric area 51 by reason of the movable contact 256a being separated from the contact 256v. This allows the load button 264 on the projector to pop up causing the slidechanging mechanism in the projector to complete its cycle. Completion of the cycle causes the selected slide, which was positioned adjacent the gate, to be lowered into the gate. When the slide-changing cycle is completed, the contact 263a is disengaged from the contact 2630 thereby resulting in deenergization of the relay 232, this resulting in movement of the contacts 258a, 259a to the position illustrated in FIG. 20, thereby completing a cycle of operation.
As mentioned above, the diodes 33, 34 cause the contact strips 49, 50 to be provided respectively with a plus and minus polarity. This determines the direction of rotation of the motor 162 and consequently the direction of rotation of the seeking contact. In the cycle of operation just explained, it will be appreciated that if the operator had rotated the knob 18 in the other direction, l.e., in a counterclockwise direction (with reference to FIG. 20), the contact strip 50 would have been brought into engagement with the seeking contact thereby resulting in current flow through the motor 162 in the opposite direction. It will be appreciated that by reason of this feature the slide tray will always be rotated in a direction which will result in the minimum amount of rotation to bring the selected slide to the projection gate. Or in other words, the slide tray will never be rotated in excess of 180. It will be obvious that because of this feature the random selection system of the present invention can accommodate so-called box-type slide trays. This feature may be referred to as providing shortway home or minor arc operation.-
It will be appreciated that when the selector switch 24 is in the 80-slide position, the operation is the same as described above. In this case, the switch actuator 101 is positioned for disconnecting the seeking contact 71 and connecting the seeking contact 82 in the circuit. The seeking contact 82, which has a random relationship with the seeking contact 71, is rotated at a greater angular rate as explained below. This 80- slide tray will also be rotated at a greater rate by reason of the construction of the teeth on the same and the teeth on the drive gear 196, as will be explained in detail below. Inother words, the drive gear 196 and the commutator shaft 173 continue to rotate at the same rate, the rotor in the stepping rotor turns at the same rate in synchronization with the commutator shaft and therefore the pinion 95 is rotated at the same rate, and the gear 74 is rotated'at a greater rate in synchronization with the 80-slide tray.
The construction for driving the circular tray 198 and another 80-slide tray atdifferent rates from the gear 196- which is always rotated at a constant rate is shown in FIGS. 23 through 26. Referring particularly to FIGS. 23 and 24, the tray 198 is provided with 100 teeth 197. It will be noted these teeth are greater, in terms of arcuate extent, than the valleys or notches between the teeth. The teeth 197 may be defined as being the result of laying out 200 teeth on the tray 198 and then forming or cutting every other tooth to provide the I teeth as shown.
The drive gear 196 is shown in detail in FlG.,25. This gear is provided with teeth 196a shaped for complementary engagement with the tray teeth 197. when the gear 196 is rotated through one increment which in the present embodiment is 36, i.e., 360. divided by l0 teeth, the tray 198 is moved through a one-tooth increment of 3.6 (360 divided by 100 teeth) for indexing the tray to present the successive slide-receiving space therein adjacent theprojection gate.
The teeth 270 of a 80'slide tray 271 are shown in FIG. 26. The outside diameter of such teeth is the same as the outside diameter of the teeth 197 on the tray 198. It will be understood there are 80 teeth 270. In the embodiment according to the present invention, these teeth are formed by swinging a -pitch rack tooth cutter through l8 on each side of the radius 2700. It will be noted this technique provides the teeth 270 with curved faces 27%. It will be realized that when the gear I96 is stepped through one increment (36) the tray 271 will be rotated through 4.5", i.e., 360 divided by 80 teeth. The tray 271 has this movement imparted thereto by being accelerated due to the action of the teeth 196a engaging the arcuate or curved tooth surfaces 270b. In other words, there is cooperation between the surfaces 270!) and the teeth 196a in the nature of a cam operation to accelerate movement of the tray 271 such that one increment of movement of the drive gear 196 serves to rotate the tray 271 for positioning a successive slide-receiving space therein adjacent the projection gate.
It will be understood that the teeth on the contact gears 62, 74 are fashioned in a similar manner such that these gears are driven at different rates from the pinion 95 which is rotated at a constant rate. In the embodiment according to the present invention, the l00-slide gear 62 is provided with 150 teeth of conventional construction, the spaces or valleys between the teeth .being of the same size and shape (but oppositely disposed) as the teeth themselves. The gear 74 has the same outside diameter as the gear 62. However, the gear 74 according to the embodiment shown herein is provided with 120 teeth 75. In forming these teeth, the depth of the cut was 0.65
inches, whereas the depth of the cut for the teeth 64 was 0.045 inches. The teeth 75 and the spaces therebetween are of the same size and shape (but in oppositely disposed relation) and are of course somewhat larger than the teeth 64 since there are fewer of the former than the latter. This gear construction results in the pinion rotating the gears 62, 74 at different angular rates.
It is to be understood the present invention is not limited to accommodating slide trays wherein one tray contains slide-receiving spaces and the other tray contains 80 slidereceiving spaces. It will be appreciated the embodiment of the invention disclosed herein can be readily adapted to accommodate two forms of slide trays having slide-receiving spaces differing in number from each other and being other than 80 or 100, so long as the difference in slide-receiving spaces between the trays is not unduly large with respect to the total number of spaces in the trays.
It will be understood the slide tray 198 may be stepped in either direction one space at a time by actuation of the advance and reverse" buttons 21, 22. Actuation of the button 21, for example, will cause the disk 28 to be rotated in the proper direction by reason of the engagement between the fingers 140, 141 (FIG. 14) engaging the detent formations 46, 47. This will result in the appropriate contact strips 49, 50 being brought into engagement with the seeking contact which is connected in the circuit. This actuation of the button 21 will close the contacts 146, thereby establishing a circuit as explained above for rotating the tray a distance represented by one space therein. Actuation of the button 22 will result in the other contacts 49, 50 being brought into engagement with the operative seeking-contact resulting in rotation of the tray in the other direction. The detent formations are dimensioned such thatthe formations 46 and 47 engaged by a detent ball will be detented through an arcuate increment which will result in the tray being rotated one increment defined by one slide-receiving space. The buttons 21, 22 may be successively operated for sequentially projecting the slides in the tray. I
It will be observed that the drive motor 162 is shunted by both switches 257, 259. Accordingly, the drive motor cannot be energized until after energization of both the relay 231 and the relay 232. The latter relay is not energized until the slidechanging mechanism in the slide projector has proceeded through a half cycle for returning a slide to its space in the tray. Accordingly, this feature prevents the slide tray from being rotated prior to the time the slide is returned to its space in the tray.
It will also be apparent this double-shunt arrangement for the drive motor 162 causes the latter to be dynamically braked as soon as the relay 231 is deenergized. This causes the tray to be positively stopped when the selected slide-receiving space is positioned adjacent the projection gate. As just mentioned above, the relay 232, which controls the switch 259, is not deenergized until a slide is returned to the projection gate.
When the random selection system according to the present invention is not being used, the slide projector 14 may still be operated without removing the unit 12 from the projector. The button 199 is lifted for disengaging the drive gear 196 from the teeth 197 on the slide tray. This action also releases the disabling switch mentioned above thereby placing the deenergized projector drive system into operation. The load button 264 on the projector may be operated by actuation of a button 2240 (FIG. 1) which is mounted on top of the pin 224.
As mentioned above, the present invention is not to be limited for use with the particular slide projector disclosed in the above-mentioned Hall application. However, to the extent the Hall application may be relied upon for a complete understanding of the present invention, the disclosure in the aforementioned Hall is incorporated herein by this reference thereto.
It will be appreciated that it is within the scope of the present invention to have the attachment unit 12 formed as an integral part of an associated slide projector. In such an arrangement, the motor 162 can serve as the sole drive motor for the tray rotating the latter upon operation of the random selection system and also rotating the tray when the normal tray-indexing or advance mechanism is used.
It will be understood the present invention permits the control unit to be remotely disposed with respect to the projector and connected thereto by a cable having a minimum number of conductors. in the embodiment according to-the present invention, only eight conductors are contained within the extension cable and therefore a standard eight-conductor cable can be used. This important feature results from the nature of the stepping motor with its remote commutator which requires, in the embodiment shown, only three wires for connecting the commutator to the rotor. The unique stepping motor with this remote commutator maintains precise synchronization between rotation of the slide tray and the seeking contacts for precisely locating any randomly selected slide space at the slide projection gate of the projector.
l. A remotely operated random selection system for a slide projector of the type having a slide tray and motor-driven indexing means therefor, said system comprising:
a. a control unit separate and remote from said projector comprising a motor, a seeking contact driven in an arcuate path by said motor, contact means defined by two separate segments arranged in an arcuate path for alternate engagement by said seeking contact; and manually operable selection means associated with said contact means for establishing the extent of movement of said seeking contact to effect a predetermined circuit condition;
b. a commutator mounted on said projector and having the rotatable component thereof driven by said motor-driven indexing means;
c. said motor-driven indexing means including a reversible motor;
d. a cable between said control unit and said projector electrically connecting the motor and the commutator to cause rotation of the former in synchronization with the rotation of the rotatable component of the latter; and
e. circuit means connecting the seeking contact and the segments of said contact means with the reversible motor for establishing either forward or reverse signals for each selected circuit condition, depending on which of said segments is engaged by said seeking contact to alternately energize the reversible motor in forward and reverse directions. 1
2. Random slide selection means for a slide projector of the type having a slide tray with a plurality of slide-receiving spaces therein, said means comprising:
a. drive means including a drive motor for indexing the slide tray;
b. a DC stepping motor having a remote commutator, which commutator includes a rotary element driven by said drive means;
c. a seeking contact driven in an arcuate path by the rotor of said stepping motor; 7
d. nonconductive support means mounting an arcuate contact strip arranged to be wiped by said seeking contact and defining a dielectric area adjacent one end of said strip;
e. control means for selecting a number corresponding to the selected space in the tray, including means for positioning said contact strip with respect to said seeking contact to establish an initial spatial relationship between the former and the latter; and circuit means including the drive motor, the seeking contact and the contact strip for establishing a first contact condition when said seeking contact wipes said strip and a second circuit condition when said seeking contact reaches said dielectric area, said first circuit condition causing the drive motor to be energized and said second circuit condition causing the drive motor to be deenergized.
3. The random slide selection means according to claim 2 further defined by:
a. another arcuate contact strip on said support means and having one end thereof adjacent said dielectric area and adapted to be wiped by said seeking contact alternately with said first-mentioned contact strip;
b. said circuit means including rectifying means providing said first strip with positive and said another strip with negative DC voltage;
c. said drive motor being of the reversible type; and
d. said circuit means also including said another strip for alternately energizing said drive motor in forward and reverse directions depending on whether said first strip or said second strip is being wiped by said seeking contact.
4. The random slide selection means according to claim 2 further defined by:
a. another seeking contact arranged for wiping engagement with said contact strip;
b. means for driving said another seeking contact from said rotor at a different angular rate from the rate of angular movement of the first-mentioned seeking contact; and
. selector means for alternately placing said seeking contacts in said circuit means whereby said random slide selection means may accommodate another slide tray having a number of slide-receiving spaces different from the number of slide-receiving spaces in the first mentioned tray.
5. In a slide projector of the type having a projection gate and a slide tray including a plurality of slide-receiving spaces, a system for presenting at said gate any one of said spaces selected at random comprising:
a. a drive motor and means driven thereby for alternately indexing the tray in forward and reverse directions;
b. a commutator-transmitter including a rotatable element and means for mechanically rotating the latter by said drive motor in synchronization with the indexing movement ofsaid tray;
c. motor means remotely associated with said commutatortransmitter and including a rotor which is rotated in synchronization with said rotatable element in response to signals generated by the commutator-transmitter as a result of rotation of the rotatable element;
d. a seeking contact and means connecting the same with said rotor for being driven in an arcuate path thereby;
e. selector contact means having support means mounting first and second contact strips with adjacent ends thereof in spaced relation and defining a dielectric area therebetween, said contact strips being arranged in an arcuate path for wiping engagement by said seeking contact;
. slide selection means associated with said selector contact means and operable to establish the extent of movement of said seeking contact which is necessary to effect a first contact condition, a second contact condition being effected during movement of said seeking contact; and
g. circuit means connected to said drive motor, said seeking contact and said selector contact means and adapted to cause deenergization and energization of said drive motor upon the occurrence of said first and second contact conditions, respectively, said circuit means including rectifying means providing said first and second strips with positive and negative DC voltage, respectively, during the occurrence of the second contact condition to alternately rotate the drive motor in forward and reverse directions depending on whether said first or second strip is being wiped by said seeking contact.
6. In a slide projector of the type having a projection gate and a slide tray with a plurality of slide-receiving spaces therein, a system for presenting at said gate any one of said spaces selected at random comprising:
a. a drive motor and means driven thereby for alternately indexing the tray in forward or reverse directions;
b. a three-bar commutator-transmitter including a rotatable element;
0. means mechanically connecting said rotatable element with said drive 'motor for rotating the former in synchronization with the indexingmovement of said tray;
d. a multiconductor extension cable including three conductors connected to said commutator-transmitter;
e. a random selection control unit 'remote from said projector and including:
1. motor means connected to said three conductors and including a rotor adapted to be rotated in synchronization with said rotatable element in response to signals generated by the commutator-transmitter as a result of rotation of the rotatable element,
. a seeking contact and means connecting the same with said rotor for being driven in an arcuate path thereby,
. selector means having support means mounting first and second contact strips with adjacent ends thereof in space relation and defining a dielectric area therebetween, said contact strips being arranged in an arcuate path for wiping engagement by said seeking contact,
4. slide selection means associated with said selector contact means and operable to establish the extent of movement of said seeking contact which is necessary to effect a first contact condition when said seeking contact engages the dielectric area, a second contact condition being effected during movement of said seeking contact; and
f. circuit means connecting said drive motor, said seeking contact and said selector contact means via an extension cable and adapted to cause deenergization and energization of said drive motor upon occurrence of said first and second contact conditions respectively, said circuit means including rectifying means providing said first and second contact strips with positive and negative DC voltage, respectively, during the occurrence of the second contact condition to alternately rotatethe drive motor in forward and reverse directions depending on whether said first or second strip is being wiped by said seeking contact.
7. The system according 'to claim 6, wherein the total is engaged b said seeking contact, the motor being deenerglzed y arrival of the seeking contact at sai dielectric area; and g. manually operated selection means including indicator means for rotating said disk in either direction for bringing one of said strips into engagement with said seeking contact for establishing an initial spatial relationship between the latter and said dielectric area. 9. The system according to claim 8 further defined by:
. said circuit means including a random selection initiate switch" and a single-slide initiate switch," which switches are connected in parallel and are of the normally open type;
b. a manually operated one-slide advance actuator" and a manually operated one-slide reverse actuator";
. mechanism connecting each of said actuators with said single-slide initiate switch for closing the latter upon actuation of either of said actuators; and
d. stepping means adapted to engage said disk and operated by each of said actuators for stepping said disk in advance and reverse directions in response to actuation of said advance actuator and said reverse actuator, respectively.
10. The system according to claim 8 further defined by:
a. a second seeking contact mounted for being driven by said rotor in an arcuate path for alternate wiping engagement with said contact strips at an angular rate of movement different from the rate of movement of said firstmentioned seeking contact; and
b. selector switch means for alternately placing said first and second seeking contacts in said circuit means thereby adapting said projector to accommodate another tray having a number of slide-receiving spaces different from the number of slide-receiving spaces in said first-mentioned tray.
11. The system according to claim 10 further defined by:
a. said indicator means including first and second numerical indicia means corresponding respectively to the number of slide-receiving spaces in said first'mentioned tray and said second-mentioned tray;
b. operating means for said selector switch means; and
c. masking means shiftably mounted for alternately obsecuring at least a portion of saidfirst and second indicia number of conductors in said extension cable is not in excess of eight,
8. in a slide projector of the type having a projection gate and. a slide tray with a plurality of slide-receiving spaces therein, a system for presenting at said gate any one of said spaces selected at random comprising:
and a slide tray with a plurality of slide-receiving spaces, a system for presenting at said gate any one of said spaces a. drive means including a reversible drive motor for alternately indexing the tray in advance and reverse directions;
and means mechanically rotating the same by said drive motor in synchronization with indexing movement of said tray;
. receiving means remote from said commutator'transmitter and including motor means having a rotor associated with said commutator-transmitter wherein the rotor is rotated in synchronization with said element in response to signals generated by the commutator-transmitter as the result of rotation of the rotatable element;
d. a rotatably mounted disk having first and second arcuate contact strips thereon with ends of the strips being in spaced relation and adjacent a dielectric area;
e. a seeking contact mounted for being driven by said rotor in an arcuate path for alternate wiping engagement with said strips;
f. circuit means connecting said reversible drive motor, said strips and said seeking contact, which circuit means includes rectifying means providing said first and second strips with positive and negative DC voltage, respectively, the circuit means being adapted alternately to energize said drive motor in forward and reverse directions as determined by whether said first strip or said second strip selected at random comprising:
a. indexing means including a reversible electric motor and an indexing member driven thereby, which number is engageable with a slide tray for indexing the latter in forward and reverse directions in response to forward and reverse directions in response to forward and reverse energization of said motor, respectively;
b. circuit means connected with said motor and including selector means for one-at-a-time selection of numbers corresponding to the spaces in the associated slide tray;
0. said selector means including relatively movable contacts for establishing a discreet spatial relationship of such contacts for each number selected by the selector means and for establishing forward or reverse signals for each of said contact relationships to alternately energize said motor in forward and reverse directions which results in the minimum amount of movement of said indexing member 6 5 to present the selected tray space at said gate.
13. The system according to claim 12 wherein said relatively movable contacts include a pair of arcuate contacts movable in response to operation of said selection means and a seeking contact driven in synchronization with said indexing means and arranged for one-at-a-time wiping engagement of said arcuate contacts, said circuit means providing said arcuate contacts with respective plus and minus polarity.