US3077685A

US3077685A - Display register

Info

Publication number: US3077685A
Application number: US39288A
Authority: US
Inventors: Otto P Geilich
Original assignee: Teletype Corp
Current assignee: AT&T Teletype Corp
Priority date: 1960-06-28
Filing date: 1960-06-28
Publication date: 1963-02-19
Anticipated expiration: 1980-02-19

Description

Fd). 19, 1963 o. P. GElLlcH 3,077,685

' DISPLAY REGISTER Filed June 28, 1960 3 Sheets-Sheet l INVENTOR OTTO R GEILICH Sym ATTORNEY O. P. GElLlCH DISPLAY REGISTER Feb. 19, 1963 ws 1N E n Feb. 19, 1963 o. P. GExLlcH 3,077,685

DISPLAY REGISTER Filed June 28, -1960 5 Sheets-Sheet 5 mvENToR F'G- 9. oTTo P. GElLlczl-s ATToRNrf States This invention relates to display devices and more particularly to a display device wherein the characters to be displayed are printed on flexible strips which may be advanced step by step to present the characters to a display position.

It is an object of the present invention to provide a simple and high speed device for displaying characters selectively.

Another object of the invention is the provision of a multiple position character display device including a plurality of character bearing elements which may be advanced individually step by step to present the characters on them to position to be read and wherein a common drive means drives all of the character bearing elements that are selected to be driven.

In accordance with one embodiment of the invention the characters to be displayed are printed on flexible strips wound on spring powered rewinding drums from which the strips are unwound step by step by a pawl and ratchet arrangement. In the pawl and ratchet arrangement there is one pawl and one ratchet driven drum individual to each strip and a cam shaft common to all of the pawls carries a cam individual to each pawl for actuating it to drive its associated ratchet wheel. The pawls are normally held out of operative association with their respective cams by electromagnets individual to them whereby when an electromagnet individual to a particular pawl is actuated its associated pawl will be driven by the cam individual to it to advance its associated driven drumone step. Each of the ratchet driven drums has associated with it a retainer pawl and a release magnet which upon operation will release both the driving pawl and the retainer pawl from engagement with its associated ratchet wheel to permit the spring powered rewinding drum to return the llexible strip to its original position.

A more complete understanding of the invention may `be had by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a front elevational view of an apparatus embodying the features of the invention, par-ts being broken away more clearly to illustrate some of the parts behind them;

FIG. 2 is -a top plan view of the apparatus shown in FIG. l, parts being broken yaway to conserve space;

FIG. 3 is a sectional View, taken substantially along the line 3 3 of FIG. 1, in the direction of the arrows, showing the right side of one of a plurality of individual display units;

FIG. 4 is a vertical View in elevation, taken substantially along the line 4 4 of FIG. 1, in the direction of the arrows, showing the other side of the individu-al unit shown in FIG. 3;

FIG. 5 is a vertical sectional view, taken substantially along the line 5 5 of FIG. 3, in the direction of the arrows showing the pawl and ratchet arrangement in eleva-tion;

FIG. 6 is a fragmentary View, showing the flexible strip with the characters on it as it is associated with a pair of contact actuators used in controlling movement of the strip;

FIG. 7 is a fragmentary perspective view showing the pawls;

FIG. 8 is a sectional View, taken substantially along the line 8 8 of FIG. 2, in the direction of the arrows, showing details of a rewinding drum, and,

FIG. 9 is a circuit diagram showing the manner in which the operation of the apparatus may be controlled.

Referring now to the drawings wherein like reference characters designate the same parts throughout the several views, it will be seen that, in the embodiment of the invention disclosed herein, there are three display positions or

register units

11, 12 and 13, all of which are of the same construction. It will be understood however, that any number of positions or units could be used without departing from the scope of the invention. The display positions or

register units

11, 12 and 13 are mounted on a base plate 14 on which there is suitably supported a cam shaft 15, common to all of the units. Cam shaft 15 has iixed to it a series of

cams

16, 17 and 18, one cam being individual to each of the

units

11, 12 and 13, respectively. The cam shaft 15 is mounted for rotation in bearing blocks 19 and 20 and is arranged to be driven by a gear 21 which in turn may be driven from any suitable power source (not shown).

Since all of the

units

11, 12 and 13 are of exactly the same construction, only the unit 11 has been shown in `detail and this unit will be described in greater detail than the other two units. The display position -or register unit 11 comprises a main support bracket 26 (FIG. 5) comprising a bracket base 27 having extending normal to it a pair of side plates 28 and 29 which preferably are formed integrally with the bracket b-ase 27. As may best be seen by reference to FIG. 4, the bracket base 27 has `a U-shaped magnet support 30 fixed to it for supporting an electromagnet 31 in operative relation to an armature 32. When current is applied to the electromagnet, it will attract the armature 32 which is mounted on a latch plate 33 that is piv-oted on the upper leg of the magnet support 3i) and is urged to rock in clockwise direction (FIG. 3) (counterclockwise direction FIG. 4) by a contractile spring 34. The spring 34 has one end attached tothe upwardly projecting end of the latch plate 33 and has its other end attached to a pin 35 which is in turn mounted on the upper leg of the magnet support 30. The lower end of the latch plate 33 normally engages in Ia notch 36 formed in the end of a pawl actuating lever 37 which is pivoted on a pivot stud 38 that is in turn fixed to the side plate 28 as seen most clearly in FIGS. 2 and 7. The pawl actuating lever 37 (FIG. 4) has a portion of it, intermediate the end having the notch 36 and the pivot stud 38, which portion lies in the path of the cam 16 on cam shaft 15 and the left end of the pawl actuating lever 37 as viewed in FIG. 4 has a contractile spring 39 attached to it which is also attached to a bracket 40 lxed v to the magnet support 30.

When the electromagnet 31 is energized, it will attract its armature 32 to move the lower end of the latch plate 33 out of the notch 36 on the pawl actuating lever 37 and the spring 39 will then pull the left end (FIG. 4) of the pawl actuating lever 37 up into engagement with the low portion of the cam 16. This will result in the pawl actuating lever 37 rocking in a clockwise direction (FIG. 4) and then as the cam shaft 15 rotates, the cam 16 will rock the pawl actuating lever 37 in a counterclockwise direction (FIG. 4). Pivotally attached to the right end of the pawl actuating lever 37 (FIG. 4) the left end (FIGS. 3 and 7) is a driving pawl 45 that is urged into engagement with the teeth of a rotatable ratchet member 46 (FIG. 3) by a contractile spring 47 attached to the pawl actuating lever 37 and the pawl 45. Also associated with the ratchet member 46 is a retaining pawl 48 which is bent to U-shape adjacent its bottom end as seen most clearly in FIGS. S and 7 to provide dual bearings into which a pivot stud 49 extends. retaining pawl 48 is urged into engagement with the The upper end of the ratchet 46 by a contractile spring 5t) which is attached to the bottom end of the pawl 4S below the pivot stud 49 and to a pin 51 (FIG. 3) fixed to the bracket base 27.

Ratchet member 46 has suitably xed to it a tape winding drum 52 (FIGS. 3 and 5) and the ratchet 46 and drum 52 are rotatably mounted on a bearing stud 53 suitably fixed to the side plate 28. A stop pin 54 is fixed on the side of the ratchet member 46 and extends into the path of a rotatable stop lever 55 that is freely rotatable about the bearing stud 53 and has an extension 56 which projects laterally to engage with a xed stop pin 57 that is mounted on the side plate 28. By means of this arrangement the driving pawl 45 may drive the ratchet member 46 and the winding drum 52 through one complete revolution and approximately a second complete revolution. In the lirst revolution of the winding drum 52, the pin 54 will move away from the lever 55 in a clockwise direction as indicated in FIG. 3 and after completing approximately one complete revolution the pin 54 will engage with the stop lever S and carry the stop lever 55 around with it to a point where the stop lever 55 will approach the stop pin 57. When the

pawls

45 and 48 are withdrawn from engagement with the ratchet member 46 and the ratchet member 46 and winding drum 52 are thus released by the pawls, the drum 52 and ratchet member 46 may be rotated in the opposite direction that is counterclockwise in FIG. 3 until the pin 54 engages the stop lever 53 and carries it around with the ratchet member 46 to a point where the stop lever 65 engages the stop pin 67 which is the normal unoperated position of the ratchet 46 and drum 52.

Each set of

pawls

45 and 48 has associated with it a retracting member 63 that as seen most clearly in FIGS. 2, 3, 5 and 7, is provided with a pair of guide projections 64 and 65 on its right side (FIG. 5) and a guide projection 66 on its left side which serve to guide the

pawls

45 and 48 adjacent to their upper ends to maintain them in proper position with respect to the ratchet member 46. The retracting members 63 is also provided with a laterally extending portion 67 which terminates in a bail like portion 68 that extends across in front of both of the

pawls

45 and 48. The retracting member 63 is mounted on a plunger 69 (FIG. 3) of a solenoid 70 that is mounted on a bracket 71 in turn suitably fixed to the bracket base 27. When the solenoid 70 is energized it will attract its plunger 69 and move the retracting member 63 to the left as viewed in FIG. 3 to withdraw both of the pawls 45 and `48 from engagement with the ratchet member 46.

Suitably attached to the winding drum 52 is one end of a translucent tape 72 on which are printed characters which may be numbers as shown in FIG. 6 or which may be letters. The tape 72 has its other end attached to a spring powered rewinding drum 73 which is in turn rotatable about a stud shaft 74 mounted on the side plate 29. A clock spring 75 has its inner end fixed to the stud shaft 74 and has its outer end attached to the inner surface of the drum 73 for tending to drive the drum 73 in the direction indicated by the arrow 76 (FIGS. 3 and 8). The lower course of the tape 72 is directed from the drum 73 to an idler roller 77 and then over a second idler roller 78 to the winding drum 52. The vertical course of the tape 72 between the

idler roller

77 and 78 passes between an electric lamp 85 and a light shield 86 (FIGS. l, 2 and 3) in which there is formed a viewing aperture 87. The light shield 86 is suitably fixed to the side plate 29 of the main support bracket 26 and extends across the front of the apparatus a sutiicient distance to prevent an appreciable amount of light from radiating toward the front of the apparatus except in the area of the aperture 87. Thus characters on the tape 72, as they are moved into position between the lamp 85 and the aperture 87, will be clearly visible at the front of the apparatus. The lamp 85 is mounted in a suitable bracket 88 mounted on a post 89thatris in turn supported by the bracket 71.

The tape 72 is not of the uniform width throughout its length but is provided with a narrow mid-portion 90 which terminates in shoulders 91 and 92 (FIGS. 6 and 9) for cooperation with a pair of

actuators

93 and 94, respectively. Thus as the tape 72 approaches the end of its travel in one direction, the shoulders 91 will engage the switch actuator 93 to actuate a switch 95 and as the tape 72 approaches the end of its travel in the opposite direction, the shoulders 92 will engage the switch actuator 94 to close a switch 96.

As shown in FIG. 6 the tape 72 has figures printed on it and the iigure 2 is approaching the switch actuator 94. The tape 72 is of such length that at the time the shoulder 92 engages the switch actuator 94 and causes it to actuate its associated switch the figure 9 will be in position just behind the aperture 87 and in front of the electric lamp 85.

While the display position or

register units

11, 12 and 13 are all identical structurally, the description of the utilization of the apparatus will be facilitated by distinguishing between some of the parts by applying a different reference character to them. Consequently, the parts in the positions or

register units

12 and 13 which correspond to parts in the register unit 11 have had the suffixes A and B respectively added to them. For example, in the register unit 11 the electromagnet, which trips the pawl actuating lever, is designated by the reference numeral 31, whereas, in unit or position 12, it is designated 31A and in Unit 13 it is designated 31B.

The apparatus of the present invention may be used as a counter or as any other type of display unit. When the apparatus is used as a counter the figures 0 and 1 to 9 are printed on the

tapes

72, 72A and 72B. It is possible that the device might be used to display letters and letters could be substituted for the numerals when the device is to be used for displaying letters in such devices as, for example, educational devices.

One method of using the apparatus as a counter is shown in the circuit diagram of FIG. 9. For example, it might be desirable to count the revolutions of a shaft 97. This could be done by providing the shaft with a single contact actuating cam 98 which, once in each cycle of rotation of the shaft 97, will close a contact par 99 to complete an energizing circuit from grounded battery 100 through the electromagnet 31B to ground at 104. When the electromagnet 31B is energized, as will be seen by reference to FIGS. 3 and 4, the latch plate 33 will be moved out of the notch 36 in the pawl actuating lever 37, the pawl actuating lever 37 will be rocked clockwise as viewed in FIG. 4, to permit the upper surface of the pawl actuating lever to move up and engage the low portion of the cam 16. Since the shaft 15 is continuously driven, the high portion of the cam 16 will cam the left end (FIG. 4) of the pawl actuating lever 37 downwardly and consequently will raise the right end of the pawl actuating lever 37 (FIG. 4) to cause the pawl 45 to step the ratchet member 46 one step. Each time the ratchet member 46 is stepped one step it will be latched in its advanced position by the retaining pawl 48. Consequently each time one of the electromagnets 31 is energized, one step of rotation will be imparted to its associated ratchet member 46 and to the drum 52 to advance the tape 72 one step. The lirst step of movement of the tape 72 will move the figure 0 out of alignment with the lamp 85 and aperture 87 in the light shield 86 by drawing a short length of the tape 72 from the spring powered rewinding drum 73 and will move the tigure into position between the lamp and aperture.

Thus, by referring back to FIG. 9, it will be seen that each time the contact pair 99 is closed one step of rotation will be imparted to the winding drum 52, associated with the tape 72B, to advance a new character into view.

The narrow mid-portion 90 of the tape 72B is of such a length that, as the electromagnet 31B is energized the tenth time the shoulder 92B will, through its switch actuator 94, actuate the switch 96B (FIG. 9). As the switch 96B is actuated by its actuator 94 due -to the en` gagement of the actuator by the shoulder 92B on the tape a contact pair 101 will be closed first and then a contact pair 102 will be closed. Closure of contact pair 101 will connect grounded battery at 100 through the electromagnet 31A to ground at 103, thereby to energize electromagnet 31A in register unit 12. This will cause the tape 72A in register unit 12 to be advanced one step. Shortly after the circuit from battery liltl has been completed to magnet 31A switch 96B will cause the closure of contact pair 102 which will complete a circuit from grounded battery 100 through contact pairs 101 and 102 and through solenoid 70B to ground. When solenoid 70B is energized, the

pawls

45 and 48 will be withdrawn from the ratchet member 46 and the spring powered rewinding drum 76 will be driven by its spr-ing 75 to return the ratchet 46 and the winding drum 52 in back to the position shown in FIG. 3 Where the pin 54 will press the stop lever 55 against the stop pin 57.

In a similar manner after the electromagnet 31A has been energized ten times, switch 96A will be actuated through the shoulder 92A to iirst energize electromagnet 31 and then to energize solenoid 7tlA. When solenoid 70A is energized, tape 72A will be returned to its original position. Through this arrangement the register units 11, .12 and 13 may be arranged to count up to 999 and obviously, if it is desired to count higher other units may be used.

The foregoing description relates to the use of the register unit or display apparatus as a counter. If the

tapes

72, 72A and 72B had letters on them instead of iigures, the letters of the alphabet could be presented serially to the several apertures 87 or through the selective actuation of switches 110, 111 and 112, the

electromagnets

31, 31A and 31B could be operated in any desired sequence to cause their

respective tapes

72, 72A and 72B to be stepped to selected positions. Any one of the tapes 72 may be restored to its normal position without disturbing the other tapes, if it is so desired, by selectively closing the

switches

113, 114 and 115 to selectively energize the

solenoids

70, 70A and 70B.

Obviously the tapes 72 could have numerals on them in greater number than the to 9 described herein before if the device is not being used as a counter within the limitation of the size of the tape drums 52 and 73.

Although a particular embodiment of the invention is shown in the drawings and described in the foregoing specification, it will be understood that the invention is not limited to that specific embodiment, but is capable of modification and rearrangement and substitution of parts and elements without departing `from the invention.

What is claimed is:

. l. A display register comprising a continuously rotating cam, pawl driving means normally held out of operative association with said cam, a pawl for actuation by said pawl driving means, means for releasing said driving means into operative engagement with said cam, a display element, a ratchet mechanism operatively associated with said pawl for step by step actuation thereby to advance said display element step by step, a retaining pawl for holding said ratchet mechanism in any of its advanced positions, and means activated by said display element for releasing said driving pawl and said retaining pawl from engagement with said ratchet.

2. A display register comprising a continuously rotating cam shaft, a plurality of cams on said shaft, a display element individual to each of the cams on said shaft, a pawl and ratchet mechanism individual to each cam for driving its associated display element, and means selectively operable for operatively associating a pawl and ratchet mechanism with its associated cam.

3. A display register comprising a continuously rotating cam, a pawl actuating lever positioned for operative association with said cam, means normally holding said lever out of operative association with said cam, a driving` pawl for actuation by said lever, a ratchet mechamsmA for actuation by said driving pawl, a display element driven by said ratchet mechanism, means for urging said display element and ratchet to return to a predetermined position, a retaining pawl for holding said ratchet mechanism in any position to which it is advanced by said driving pawl, means operable to engage said pawl driving lever with its associated cam, means for disengaging the driving pawl and retaining pawl from said ratchet mechanism to permit the display element and ratchet to return to said predetermined position, and control means for initiating actuation of said disengaging means including a selectively operable manual switch and a switch operable by said display element.

4. A display register comprising a continuously rotating cam shaft, a lever actuating cam on said shaft, a pawl actuating lever for actuation by said cam, a driving pawl for actuation by said lever, releasable means positioned normally to hold said pawl actuating lever out of engagement with the cam, a ratchet member for actuation by said driving pawl, display means connectedl to said ratchet member for step by step advancement with said ratchet member from a predetermined position, means for urging said display means and said ratchet member to return to said predetermined position, a retaining pawl for holding said ratchet member and display means in any position to which they are advanced, and means activated by said display element after it has been advanced a predetermined number of steps forA disengaging said retaining pawl and said driving pawl from said ratchet member to render effective said means for urging the display means to return to said predetermined position. f

5. A display register comprising a cam shaft, a plurality of cams on said shaft, a pawl actuating lever individual to each of said cams, a driving pawl individual to each of said levers for actuation thereby, releasable means individual to each of said levers and positioned normally to hold its associated lever out of engagement with the cam individual thereto, a ratchet member individual to each of said paWls for actuation thereby, display means individual to each ratchet for advancement step by step with said ratchet from a predetermined position, means for urging each of said display means to return to said predetermined position, a retaining pawl individual to each ratchet for holding its ratchet member and display means in any position to which they are advanced, and means individual to each driving pawl and retaining pawl for withdrawing them from engagement with their associated ratchet member to permit the associated display member to return to its predetermined position.

6. A display register comprising a cam shaft, a plurality of cams on said shaft, a pawl actuation lever individual to each of said cams for actuation thereby, a driving pawl individual to each of said levers, a latching plate individual to each of said levers and positioned normally to block its associated lever from engagement with the cam individual thereto, an electromagnet individual to each of said latching plates for moving it out of blocking relation with its cam lever, a ratchet member individual to each of said driving pawls for actuation thereby, a retaining pawl individual to each ratchet member for holding its ratchet member in any position to which it is moved by its associated driving pawl, a drum individual to each of said ratchet members and fixed thereto for movement therewith, a translucent display tape individual to each of said drums for step by step actuation by said drum, a spring powered rewinding drum individual to each of said tapes and to which the other end of said tape is attached, means individual to each tape for guiding said tape between its ratchet driven drum and the spring powered rewinding drum, a light shield individual to each tape and disposed parallel to 7 the path of travel of its associated tape from its rewinding drum to its pawl driven drum said light shield having a viewing aperture therein, a light source positioned behind each of the tapes in the area of the viewing aperture for said tape for illuminating portions of its associated 4tape adjacent to its aperture, and means individual to each tape for withdrawing the driving pawl and the retaining pawl associated with that tape from engagement with its ratchet member to permit the rewinding drum to return the tape to the position from which it was advanced by the driving pawl.

7. A display register comprising a cam shaft, a plurality of pawl actuating cams on said shaft, a pawl actuating lever individual to each of said cams, a driving pawl individual to each of said levers for actuation thereby, a latching plate positioned normally to hold a pawl actuating lever out of association with the cam individual thereto, means for moving said latching plate to release its associated lever, a ratchet member individual to each of said pawls for actuation thereby, a drum fixed to each of said ratchet members for movement therewith, a tape having one end fixed to said drum for step by step actuation with said drum and ratchet, a spring powered rewinding drum to which the other end of said tape is attached to normally urge said iirst-mentioned drum to return to a predetermined position, a retaining pawl for holding said ratchet member and its associated drum and tape in any opsition to which they are advanced by the driving -pawl to expose different areas of the tape to a viewing position, and means for disengaging the driving pawl and the retaining pawl from the ratchet to permit the rewinding drum to return the tape and ratchet driven drum to said predetermined position.

8. A display register comprising a cam shaft, a plurality of `pawl actuating cams on said shaft, a pawl actuating lever individual to each of said cams, a driving pawl individual to each of said levers for actuation thereby, a latching plate positioned normally to hold a pawl actuating lever out of operative association with the cam individual thereto, means for moving said latching pla-te to release its associated lever, a ratchet member individual to each of said pawls for actuation thereby, a drum fixed to each of said ratchet members for movement therewith, a -tape having one end fixed to said drum for step by Step actuation with said drum and ratchet, a spring powered rewinding drum to which the other end of said tape is attached normally to urge said Erst-mentioned drum to return to a predetermined position, a retaining pawl for holding said ratchet member and its associated drum and tape in any position to which they are advanced by the driving pawl to expose different areas of the tape to a viewing position, means for disengaging the driving pawl and `the retaining pawl from the ratchet to permit the rewinding drum to return the tape and ratchet driven drum to said predetermined position, switch means actuated by said tape in one of its advanced positions, and a solenoid operated when said switch means is actuated for actuating said disengaging means.

9. A display register comprising a continuously rotating cam shaft, a plurality of lever actuating cams on said shaft, a pawl actuating lever individual to each of said cams for actuation Ithereby, a driving pawl individual to each of said levers for actuation thereby, a latch plate individual to each of said levers and positioned normally to block its associated lever from engagement with the cam individual thereto, an electromagnet individual to each of said latch plates for moving it out of blocking relation with its cam lever, a ratchet member for actuation by said driving pawl, a retaining pawl for holding said ratchet in any position to which the ratchet is advanced by its driving pawl, a drum xed to each ratchet member for movement therewith, a tape individual to each of said drums and having one end thereof fixed to said drum for step by step actuation thereby, a spring powered rewinding drum individual to each of said tapes to which the other end of said tape is attached, a light source, means individual to each of said tapes for guiding its associated tape between the spring powered rewinding drum and the drum fixed to the ratchet member, a light shield disposed along the path of travel of each of said tapes over the guiding means and having a viewing aperture whereby the portion of the tape in registry with the viewing aperture will be illuminated, said tape having a mid-portion which is narrower than the remainder of the tape to provide shoulders on the tape, switch means interposed in the path of said shoulders for actuation by said shoulders after a predetermined amount of movement has been imparted to said tape due to its actuation by 4the driving pawl, a solenoid operable under control of said switch means for withdrawing the driving pawl and retaining pawl from engagement with the ratchet member to permit Ithe rewinding drum to withdraw tape from the drum driven by the pawl thereby to return the tape to the position from which it was originally moved.

References Cited in the tile of this patent UNITED STATES PATENTS 545,883 Friederich Sept. 10, 1895 882,675 Gunter Mar. 24, 1908 890,147 Low June 9, 1908 1,052,995 Angell Feb. 1l, 1913 1,336,032 Greer Apr. 6, 1920 1,430,394 McGee Sept. 26, 1922 1,784,597 Johnson Dec. 9, 1930 2,542,515 Harvey Feb. 20, 1951 2,585,687 Sanderson Feb. 12, 1952 2,837,850 Sink June l0, 1958

Claims

9. A DISPLAY REGISTER COMPRISING A CONTINUOUSLY ROTATING CAM SHAFT, A PLURALITY OF LEVER ACTUATING CAMS ON SAID SHAFT, A PAWL ACTUATING LEVER INDIVIDUAL TO EACH OF SAID CAMS FOR ACTUATION THEREBY, A DRIVING PAWL INDIVIDUAL TO EACH OF SAID LEVERS FOR ACTUATION THEREBY, A LATCH PLATE INDIVIDUAL TO EACH OF SAID LEVERS AND POSITIONED NORMALLY TO BLOCK ITS ASSOCIATED LEVER FROM ENGAGEMENT WITH THE CAM INDIVIDUAL THERETO, AN ELECTROMAGNET INDIVIDUAL TO EACH OF SAID LATCH PLATES FOR MOVING IT OUT OF BLOCKING RELATION WITH ITS CAM LEVER, A RATCHET MEMBER FOR ACTUATION BY SAID DRIVING PAWL, A RETAINING PAWL FOR HOLDING SAID RATCHET IN ANY POSITION TO WHICH THE RATCHET IS ADVANCED BY ITS DRIVING PAWL, A DRUM FIXED TO EACH RATCHET MEMBER FOR MOVEMENT THEREWITH, A TAPE INDIVIDUAL TO EACH OF SAID DRUMS AND HAVING ONE END THEREOF FIXED TO SAID DRUM FOR STEP BY STEP ACTUATION THEREBY, A SPRING POWERED REWINDING DRUM INDIVIDUAL TO EACH OF SAID TAPES TO WHICH THE OTHER END OF SAID TAPE IS ATTACHED, A LIGHT SOURCE, MEANS INDIVIDUAL TO EACH OF SAID TAPES FOR GUIDING ITS ASSOCIATED TAPE BETWEEN THE SPRING POWERED REWINDING DRUM AND