US2947100A - Display device - Google Patents

Description

Aug. 2, 1960 L. R. LOSKILL ETAL DISPLAY DEVICE 2 Sheets-Sheet 1 Filed Aug. 21, 1959 INVENTOR. JACK E. MARTENS LAWRENCE R. Lesa/1.1.

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ATTORNEY DISPLAY DEVICE 2 Sheets-Sheet 2 Filed Aug. 21, 1959 u R s I O N T E m V A N MR 1 5 C Km c R Aw J M B mm m wn 5 DISPIJAEYJ L wr nc R oski li. Hamman r n a k M tens; a n -,aS igaQEstoI I Att Md T Q kQQmP?HM- partition of Indiana:

Filed Ang. 21 .1959, Sen 1210.. 835,236; s (glint-32)."

h n ent re ate to a display devi e or. exhi i or, nd mo ar icula y o. a metaraqn r d. chan eable exhibitor. I

In the art q fq a e b e exhibitors. ma y ifirentf y m for n n pic ures. t h viewed i ve e n-p tent: ed' throughout the yeaIS These. s st m5, vary, in. come ty a l t y. rom. me er-driven. continuously faring endless: s teenr yre disp ay devices t co p ex electronically e ntm iedide tes-.. Exhibit rs. o e yre under discussion are require jto have a life expectancy of. three years of continuous substantially trouhl'e-freeoperasuch. t a the numbe o comp ex. mov n pa t should be'keptto a Atthe same time. the. bp

.eration and appearance of the. device shouldgrnaintain 9 degreeof no e y s. 9. a tract the attent o n the average pedestrianpassingby the. devicein thenormal:

course of his daily travel,

It is, therefore, an object ofgithis invention to. provide. an. improved. display device thatcan operatecontinuouslyfon a relatively long period without; requiring serviceor, ex pensive repair.

It is another je t.qf his' nventibnta p o i e afi sn ay. a o 'h v amin m m 3 her. of o arans f creating e e if er nt mo ons. ivine; he h rmi cycle of the system.

It is still anothe bjectofjthis inyentionto. provide-an. improved. display actuator wherein the picture or,material.. to be viewed is positioned completely. into. proper; align. ment with the viewing wind'ow before it is exposed-ftowiem.

It is a still further object ofthis inyentionmtoprovide. an, improved display. actuator where; the pictureIonrnw terial being viewed is held inviewi ;position for aprea determined periodiofftime before i once. again. coyered.

And yet another object ofj'tln I, ventionis toprQvide. an improved. d p y a tua nr- .a ne mpleopera in parts that are relatively inexpensive tobnild' and'assembjle. and which. are of 'trguble-fifee andisturdy, construction.

A further object ofinvention is toprovide. an;im; proved display actuator, in which thevarious pictures or material being displayed; can be. easily. interchanged with.

new pictures. or materia l Other objects and advantages ;v will; be obvious. to those skilled in the art towhich this nvention relatesfrom the. following description talgen, connection withthe ac.-. companying drawings, wherein like reference numerals designate like parts and wherein; I

Figure 1 is a frontelevationalj view of the invention. withmost ofthe housing thereof cntaway to. Show. the. interior mechanism; I

Figure 2is a sectional" view taken alongline ZrZi of Figure 1 looking in the direction, ofl'theLarrows;

Figure 3 is" a sectionalflview. takenralong line 3 .--3 of Figure 1' and also lookingin the directipnofithe arrows;

system illustrating one manner. off-reversing t1i.- diivemotor of-the'exhibitor;

Figure 6 is an. enlarged. front eleyational yiew-ofjthe;

exhibitor in ,me hangm. .an ;mQtor m rolme ns. therefor with the shutter-in the open position;

- la.t.enteg- 1951i Figure 7' is a detail'of a portion of the tripractuator'for the motor control switch taken along the line. 7-.-7 of Figure 6;

Figure 8 is a detail taken. along line 8-.8: of Figure 6 showing the position. of the motor. controlswitch during an exhibition phase; a a

Figure 9 is a d'etailof thetrip. actuator for the motor control switch in. the phasev nextfollowing that shown in F g r 6'; r

Figure 10. is a view'corresponding toFigure 7 with the, arm of the. switchtrip rod. in. position tov be returnedto.

I its starting point in the. controlcycle; and

Figure 11 is a. view corresponding to Figure 8-showing thezposit'ionof the switch-during the shutter closingphase;

Referring more, particularly to.the drawings, wherein similar reference numerals. refer to. similar parts. through.- out the several views, 20' designates an. elongate housing preferably rectangular having an opening formed. near one end defining a window. 21. An. endless. carrier on screen 22 is arranged behind window 21 and includesa. plurality of panels or frames. 23.. each bearing a. picture a reading or other matter to be exhibitedone after anaother. Screen 22 is trained about upper and lower. rollers. 24' and 25, respectively, the upper roller 24 being driven. step by step for advancing the panel's. into viewing position through thewindow. The particular panel 23 thatis. in viewing position at any onetimemay be. illuminated as. necessary or desired and, in the event screen 22- is, made of transparent or translucent. material, lamps. may

be arranged betweenthe parallel sides-of the screen to.

shine through the panel 23. To increase the. length of. the screen andin turn its panel space, smaller rollersmay be arranged between rollers 24 and 25.. and the carrier trained thereover. For rotatably mounting rollers 24.,and- 25, the ends of each areequipped withtrunnions 26.journaledlin brackets 27, the. latter being fixed. to. the inner walls of the housing 20.

A cover or shutter ZS'for. window 21 is-slidably mount ed on or within housing.20 and has. a.power.-operated, means for positioning the shutter over the window 21. dur ing the. interval of time in which the. panels. 23.. of the screen are being shifted. The. shutter is. next moved slowly to a position to. revealithe newly positioned panel: 23. When the panel 23, is completely exposed. to.view, the shutter 28 is held inastationary positionfora pre selected period of timeafterwhichit is.slowly moved into.

position to cover the panel 23 again. Forthepurpose. of illustration, shutter 28 is. shown as being U-shaped in cross section straddling housing 20.With..the. legs or walls, of the, shutter hanging down on opposite sidesofthe hous ing, At least two pairs of .spaced rollers.29. are fastened. to the. inner wall of jtheintermediate. or bight. portion 30: of. the shutter near each. end thereoffor rollingly support: ingthe, shutter on the, upper wall .of the housing.

The power-operated means for moving shutter 2&comprises a rotatably mountedhelically threadedcshaft 3 1: driven by. areversible electric. motor. 32 throughapulley and belt transmission 33. A, nutassembly 34 is arranged. on shaft 31 to be periodically. movedbackand forth longi-.- tudinally of the shaft. Thenutassembly 34 iscOnnectedto shutter-.28 by meanslof. a bracket 35.which.is. secured: at one end to the. inner bight portion 30 ofitheshutten. and reaches to the nut assembly 3.4.through a slot.36,.ex-.- tendinglengthwise of the upper wallof thehousing.

lOne. endof threaded shaft 31 is.journa1ed-at.37 irnar plate 38 of a supporting structure within the.. housing-,, while tlie opposite end oflthe shaft isjournaled (Figure .6 in the trunnion 26of upper roller 24. For the purpose.- indicated, the outer end. of: trunnion: 26. outwardly of bracket 27' is formed into acup shape 40. An-antifricje tionbearingAl is-fi'xed.within 01111.40 and..inrturn;.re-.---

ceives the proximate unthreaded end 42 of shaft 31. By

3. reason of the antifriction characteristics of bearing 41 and the inherent frictional resistance within the screen structure, rotation of shaft 31 in bearing 41 alone creates no material torque sufficient for driving the trunnion 26 and screen 22. p 7 V Nut assembly 34 is preferably of the freewheeling antifriction type. One such assembly includes an outer casing, a plurality of bearing elements (not shown) projecting through openings in the cage and engaging the threads of the shaft 31, and circumferential tracks or shoulders within casing 43. Aside from quietness of operation and negligible frictional loss, nut structures of this type present, for certain uses, the highly desirable property of I ffreewheeling, the latter property being availed of in the present organization. By freewheeling, in the present situation, is meant that upon obstructing planetation of the cage 44, as by a stop on the shaft, the threaded drive shaft may simply continue to rotate within the assembly casing without imparting material axial thrust to the assembly casing.

Shaft 31 (Figure 6) adjacent bearing 41 is provided with a radially projecting stop pin 45 adapted, as the nut assembly reaches the end of its shutter-closing stroke (-Figure 1), to enter a notch 46 formed in the corresponding end of cage 44, whereupon axial thrust upon the casing 43 will cease and cage 44 is positively rotated at the speed of the shaft 31. A finger 47 is provided on the end of the cup 40 of the trunnion 26 and extends in overlapping relationship with the end of shaft 31. A radially extending cooperating finger 48 is provided on cage 44.-

The arrangement is timed so that the finger 48 on the cage will drivingly engage the finger 47 on the trunnion 26 immediately after stop pin 45 obstructs free rotation of the cage. driven from cage 44 through fingers 48, 47. to advance the screen 22 until the motor 32 is reversed to withdraw the shutter 28 and coincidentally separate fingers 48 50, 51 extending to the motor. A switch 52 connects the two contacts 52' and 52 together such that movement of the switch to the left causes the motor to rotate in one direction, and to the right causes, rotation of the motor in the, other direction.

Snap switch 52 is mounted on a bracket disposed near one edge 54 of screen 22. The switch, as illustrated, includes a casing 55 and a double-throw snap-acting lever 56. The outer end of lever 56 has a flat portion 57 disposed transverse to the direction of movement of said lever 56. The proximate means for operating the switch 52 includes a generally L-shaped lever 58. Lever 58 is fixed at the juncture of its arms upon an end .59 of slidable trip rod 60. Arm 61 of lever 58 is bifurcated to receive the outer flat portion 57 of switch lever 56 therebetween. Upon endwise movement of trip rod 68 to the right, as viewed in Figures 6 and 9, arm .61 can slide sidewise along the fiat end 57 of the lever without disengagement therefrom. A tension spring 62 is fastened at one end to bracket 53 and at its opposite end to the otherarm. 63 of lever 58, the arrangement being such as to tend to bias the switch lever 56 to the position of Figure 11; that is, to the position whereby the motor is reversed and starts to rotate the shaft 31 in the opposite direction so as to move the shutter 28 into position to cover the panel 23.

Arranged on the inside of the edge 54 of the screen 22 adjacent the. switch 52 is a series of small L-shaped trip brackets 64, each presenting a ledge 65 projecting into At this point, roller 24 becomes positively.

throw switch is employed with a motor having leads 49,.

the space between the respective sides of the screen. The brackets 64 are spaced apart along the edge of the screen distances corresponding to the size of the appropriate panel 23, and their path of travel is so routed that during shifting of a screen panel vertically, starting from the position of Figure 11, the ledge 65 of the next succeeding one of the brackets 64 will catch under arm 63 of the lever 58 and raise it to the position shown in Figure 8, whereupon switch 52 is snapped and motor 32 is reversed, starting movement of the shutter 28 toward the left for uncovering the panel 23. As soon as the motor is reversed the fingers 47, 48 are immediately separated from each other so that further advancement or movement of the screen is stopped. .Obviously it is desirable to leave a panel exposed for a longer interval than that required in advancing it to viewing position; and, equallymanifest, motor 32 cannot be reversed by switch 52 until arm 63 of lever 58 is disengaged from the particular bracket ledge 65 which is holding it in the cocked position of Figure 8. 1 Arranged on the end of screw shaft 31 remote from the roller 24 is a sleeve member 68 which is normally free to rotate relative to the unthreaded end portion 69 of the shaft 31. Said sleeve member is externally threaded at 70 to operate as a worm gear 71. 'A worm wheel 73 is pivotally mounted by axle 74 within housing 20 in engagement with worm gear 71. The axial ends of the sleeve member 68 are formed with notches or shoulders 75. The shoulder 75 on one end is adapted to be engaged with a corresponding shoulder 46 on the adjacentend of cage 44 of nut assembly 34. Shaft 31 is also provided with a pin 78 which is adapted to be engaged in the notch 75 on the sleeve member 68 of the worm gear. A coil spring 80 surrounds the unthreaded end portion 69 of shaft 31 and tends to push the worm assembly to the right as viewed in Figures 1 and 6.

Since the nut assembly 34 is adapted to freewheel, it follows that so long as the sleeve member 68 is disengaged from cage 44, as in the position of Figure 1 for example,

spring 80 will urge the sleeve 68 and worm gear 71 outof locking engagement with pin 78 whereupon the worm gear 71 and sleeve 68 will not rotate; that is to say, shaft 31 will simply rotate within the sleeve member 68 without imparting rotation to the worm gear 71 and worm wheel 73. On the other hand, as the nut assembly 34 moves to the left (Figure 6) its cage 44 will interlock with the adjacent shoulder 75 of the sleeve 68 for moving the sleeve 68 against the spring pressure and to the left for engaging shoulder 75 with the pin 78, whereupon worm gear 71 is rotated with the shaft 31 for driving the worm wheel 73. Upon reversal of the motor 32, the spring 8 0 will push the sleeve member 68 out of engagement with the pin 78 and to the idling position shown in Figure 1. Rotation of the worm gear 71 by the shaft 31 rotates worrn wheel 73 in the counterclockwise direction indicated by the arrow in Figure 6. The ratio of worm gear 71 and worm wheel 73 is selected to maintain shut ter 28 open for a period of time in the order of thirty seconds. a

Trip rod 60 is adapted to be slidably mounted in the housing with one end portion passing through an opening in a bracket 82 disposed adjacent to the worm wheel 73 and with the other end portion 59 passing through an opening in the switch-supporting bracket 53. The one end portion of rod 60 adjacent worm wheel 73 is bent at a right angle to the rod to provide a trigger arm 83 which is adapted to be positioned in the path of a pin 85 projecting from the face of worm wheel 73 during one portion of the cycle of'operation of the device. The opposite end portion-of the rod 60 is rigidly attached to the mid-section of lever 58 in such a relative relationship with respect to the arm 83 that when one of the brackets 64 moves the portion 63 of the lever 58 to the up position of Figure 8,. thearm 83 will be in the vertical position so that thetpinn85 willstrilre it at the appropriatethe side edgeof ledge 65, aS Shown in Figure 9,1where-- upon coil spring62 will snap the lever. 58fto theppsition fonreversing the motor, thereby moving the shutter to the right for coveringthe window 21; in this position, arm 83 011 rod 60 is brought temporarily into engagement with the wall of housing 20' and out of alignment with the pin 85 on the Worm wheel 73, as shown in Figure 10. As soon as spring 62 snaps the lever 58to the position ofFigure llfor reversingjthe rotation of themotor, the spring 86 on the rod 60 drives the rod 60. and arm 83 to the left. The arm. 83 moves to. the left past thegpin 85 on the wheel 73 and the lever 58 is in positionto be engagedi by the next bracket. 64 on the screen 22 Theshutter 28 is slowly moved to the right'until. the pin 48 on the nut 3.4 engages with the pin 47 on the'trunnion 2 6. whereupon the screen 22 is rotated. One of the brackets 64 on thescreen moves into engagement" with the portion 57 on the \lever58 for. rotating'the lever counterclockwise (Figure 8) to the motor-reversingposi tion of Figure 8. The lever simultaneously rotatesthe rod 60 and arm 83*to position the arm into an upright position to the left of the pin 85 as shown in Figure 1. The pin 48 on the nut 34 disengages from the pin 47 on the roller 24 to stop movement ofthe roller. The nut advances to the left to expose the picture on the screen 22 and when the shoulder 46 on the nut engageswiththe shoulder 75 on the sleeve member 68, the sleeve member is shifted to the left against the pressure of'the spring80f until the shoulder 75 on the sleeve member engages the pin 78 on the shaft-'31. The shutter 28 ceases'tomove in either direction for a; preselected'period oftime during which time the outward appearance of the system isstatic. The shaft rotates the sleeve member and worm gear 71 for drivingthe worm Wheel 73 in a counterclockwise direction. When the wheel 73 has completed about one full turn, the pin 85'contacts the-left side of the arm 83 and drivesthe rod:60 and lever 58'1tothe.

right until the lever 58 disengages from. the bracket 64. The motor is again reversed andthe' cycleirepeats itself.

Having thus described my invention, it is obvious that various modifications may be made in the same withoutdeparting from the spirit of my invention; hence, I do notwish to be understood as liniiting'myself to theexact form, construction, arrangement andicombinationof parts:

herein shown and described or uses mentioned;

We claim: j y

1. In a changeableexhibitor, a" housingshavinga window therein, a series of panels arranged within-saidhousnut structure for movement therewith, and means engageable with said nut structure. atone end of itsstroke for.

positioning a fresh panelwithin view of said window.

2. A changeableexhibitor comprising a housing'having: awindow therein, a series of panels: arranged Withinsaidi housing to be. positioned one after another for viewingthrough said window, movable means associated with said window f'or'concealing said panels during thepanel' changing cycle, and means for cyclically changing" said panels and withdrawing said movable means between the panel-changing operations, saidchanging means includaa ahs adcd shaft vsr ihl m ar. f r,. a na.sa d aina freewheeling nut structure: reciprocably driven along said shaft,said. movable means being connected withsaid nut structure for. longitudinal-movementtherewith, nieansengageable with said nut structure at one end of its stroke. for. positioning a .fresh panel within view; of said Window, andfmeansop'erable by the changing of said panelto reversesaidjrr otor for. withdrawal ofsaid movable means.

3; The structure asdefinedfin claim 2 including a second means operable, by said-nut structure'atthe opposite end. Qfih? travel along said shaft for again reversing said moto to rep at he, pane h operation 4': The structure as ,defined inclaim 3'wherein said sec ond motor-reversing means includes-.a time-delay mecha: nism:

5;; A cyclie exhibitor comprising a housing having a window therein, an endless screen arranged within the housing; saidscreenincluding a plurality ofpanels to be positioned" one after another, in line with said window, a

shutter mounted to be inoved'into and out of'position. to

cover said panels during the panel-changing phase, means for; cyclically'changing said panels and operating said shutter'compn'sing a threaded shaft, areversible electric r'notor-for-rQtating-s'aidshaft, ,a freewheeling nut structure reciprocably driven along said shaft, said shutter being coniiected with said nut structure. for alternate .lOn-. gitudinal-movement with respect to said window, rotatable means engageable with an element of said nut struc-. ture during the freewheeling; phase at one end of its stroke. for advancing-said 'screen, trip. means mountedalongan edge of said screen in, spaced-apart relationship, switch means operahle by'sa-idtrip means for reversing Sald-IIlOr tor for disengaging said"elementfroin.said nut structure, andmeans oper'ated by said" nut structure at the opposite end of its=stroke for" delayed; operation of said switch means -fonagain reversing said motor.

6*. A cyclic-exhibitor comprising a housing having awindow: therein, an endless screen arranged within the housing, said' screen bearing a plurality of panels or frames forexhibit one after another at said window, spacedrollers upon which said screen is trained, a shuts ter mounted to bernoved'into and out of position to cover said panels, a helically threaded shaft mounted in'axialalignrnent' with one of' said rollers, a stop pin near one. end of; said' shaft proximate tov said roller, a, fingerprojecting from said roller along said shaft, a free-. wheelingnut structure reciprocably driven along said, shaft andjhaving'a" finger projecting radially from the. cage element thereof for-driving saidscreen through said.

fingers 'when-the nut structure engages said stop pin, a. reversible motorfor rotating said'shaft, .said'shutter being connected to said nut-structurefor operation thereby, a reversingswitch for said' motor, and spaced means on I said screen engageable-with said switch for reversing said,

motor and disengaging the drivingof said screen.

7; A cyclic exhibitor-comprising, a housing having. a. window therein, an end-lessscreen arranged within the housing, said screen having. a plurality of panels or I frames forexhibit' one after, another in said window,. spaced rollers upon whichsaid screen is trained, one of said rollers beingprovided with a cupped drive truns nion, an-antifriction' bearing fixed in said cup, and a finger extending-axially from the rim of said cup, at heli-.

cal ly threaded' rot-ary shaft mounted in alignment with,

said last-mentioned roller withits proximate end jour:

naledinthe hearingof' said cup, a stop pin on said-shaft adjacent said clip, a freewheeling nut structure recip roeably: driven along said shaft and having a.finger projecting radially'fromthecageelement thereof for drivingi said: screen through said fingers when the: nut structure engages said stop pin; a shutt-er mounted to bemoved into and OJlt'Of! position-to cover 'said panels and connected tosaid nut structure m be operated thereby, a reversible-motor for. rotating said 1 shaft, reversing switch means for said motor, and spaced means on said screen engageable with said switch means for reversing said motor and disengaging the driving of said screen.

8. A cyclic exhibitor comprising a housing having a window therein, an endless screen arranged within the housing and including a plurality of panels for exhibit one after another through said window, rotatable means for advancing said screen, rotary driving means engageable with said last-mentioned rotatable means upon rotation in one direction for advancing said screen, said driving means being reversible to discontinue advancement of the screen, a shutter mounted to be moved into and out of position to cover said window, said shutter being connectedto be moved by said driving means to one or the other of said positions depending upon the direction of motion of the driving means, a reversible electric motor for said driving means, a reversing switch for said motor, and spaced means on said screen engageable with said switch for reversing said motor and disengaging the driving of said screen.

9. The structure as defined in claim 8 wherein there is provided a second means for reversing said switch to repeat the step of advancing the screen and shutter-closing operations, said second means including a worm gear and worm wheel actuated by said driving means when disengaged from said rotatable means, a pin projecting from the face of the worm wheel, a trip rod mounted to slide endwise and having one end bent to normally lie in the path of said pin, the opposite end of said trip rod extending to and operable to actuate said switch upon shifting of the trip rod by said pin.

10. A cyclic exhibitor comprising a housing having a window therein, an endless screen arranged within said housing and including a plurality of panels for presentanon one after another at said window, a shutter for covermg said panels during advancement of said screen, power-operated means designed to close said shutter and advance said screen during movement in one direction, sa d power-operated means including a reversible elecill C motor, a snap switch disposed adjacent an edge of said screen for reversing said motor, a lever system for actuating said switch, a plurality of spaced trip devices, one for each panel, carried along said edge of the screen for operating said lever system as a fresh panel is presented at said window, each said trip device being adapted to actuate said switch for reversing said motion of the screen to terminate advancement of said screen and retraction of said shutter, second means for operating said switch to again reverse said motor to close said shutter and advance said screen, said second means including a worm gear and worm wheel driven by said motor after the first-mentioned reversal thereof, a pin carried by said worm wheel, and a slidable trip rod having means disposed in the path of said pin, the opposite end of said trip rod being connected to said lever system.

11. Means for cyclically advancing an endless screen carrying a plurality of panels to be presented, said screen being trained over spaced rollers, means for driving one of said rollers intermittently in the same direction for advancing said panels, said means including a helically threaded shaft, a reversible electric motor for rotating said shaft, a nut structure of the freewheeling type reciprocably driven along said shaft, a stop pin on each end portion of said shaft, means operable upon impingement of said nut structure against one of said stop pins for driving said rollers in said direction, a reversing switch for said motor, means on said screen for actuating said switch after advancement of a fresh panel to reverse the travel of said nut structure, and second means for subsequently reversing said switch, said second means including a sleeve member on the remote end portion of said shaft, the exterior of said sleeve member being cylindrical and threaded to provide a worm gear, spring means biasing said second'means away from its adjoining pin, whereby the first nut structure when moving away from carrier-advancing position will push the sleeve member into engagement with said pin and thus cause driving of said worm gear, a worm wheel driven by said worm gear, a pin on the side of said worm wheel, a slidable trip rod having at one end an arm disposed in the path of said last-named pin and the opposite end extending to and controlling said reversing switch. 12. The apparatus as defined in claim 11 further including a shutter for said panels, said shutter being connected to said reciprocable nut structure and shifted thereby into and out of position to cover said panels.

13. In a changeable exhibitor, an elongate housing designed to be supported on an edge, a window in a side wall near one end of said housing, a series of panels arranged in said housing for presentation one after another within said window, a U-shaped shutter straddling said housing, antifriction means between the intermediate portion of the shutter and the top wall of said housing for reciprocably mounting said shutter for movement to a position to obstruct vision through said window during the panel-changing cycle, means for cyclically changing said panels and withdrawing the shutter, said last means including a motor-driven threaded shaft, means for periodically reversing said motor, and a freewheeling nut structure reciprocably driven along said shaft and designed to shift said panels upon reaching one end of its stroke, said shutter being operatively connected to said nut structure for simultaneous movement of said nut and shutter.

14. In a changeable exhibitor, a housing having a window therein, an endless screen having a series of panels arranged in said housing for presentation one after another at said window, means for cyclically changing said panels including a motor-driven threaded shaft, a freewheeling nut structure reciprocably driven along said shaft and designed to shift said panels upon reaching one end of its stroke, switch means for reversing said motor, means controlled by the advance of said panels for operating said switch means at said one end of the stroke of said nut structure, and means for reversing said switch means at the other end of the stroke of said nut structure comprising a sleeve member freely rotatable on the opposite end of said shaft, said sleeve member having a cylindrical casing with the exterior thereof formed as a worm gear, a pin projecting radially from the end of said shaft adjacent said sleeve member, a spring urging said sleeve member away from said pin and into idling position, the nut structure on one stroke being adapted to push the sleeve member against said pin to cause said worm gear to rotate, a worm wheel operatively engaging said worm gear, and means actuated by said worm wheel for reversing said switch means.

15. In a changeable exhibitor, a housing having a window therein, an endless screen within the housing having a series of panels for sequential presentation at said window, means for cyclically advancing said panels including a motor-driven threaded shaft, a freewheeling nut structure reciprocably driven along said shaft and designed to shift said panels upon reaching one end of its stroke, snap switch means for reversing said motor, a spring-biased actuating lever for said switch, a slidable trip rod mounting said actuating lever for sidewise movement, means for actuating said lever during the period said reciprocating nut structure is at said one end of its stroke comprising a series of spaced ledge elements attached to an edge of said screen in position to engage said actuating lever and deflect it to reversing position against the bias of said spring, and means operated under control of said reciprocable nut structure when at the other end of its stroke for sliding said trip rod to clear said actuating lever of said ledge element whereby the spring again reverses the switch.

No references cited.

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