CA1052096A - Changeable printed alphanumeric display system - Google Patents
Changeable printed alphanumeric display systemInfo
- Publication number
- CA1052096A CA1052096A CA245,005A CA245005A CA1052096A CA 1052096 A CA1052096 A CA 1052096A CA 245005 A CA245005 A CA 245005A CA 1052096 A CA1052096 A CA 1052096A
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- Canada
- Prior art keywords
- tape
- character
- display
- rollers
- segments
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Displays For Variable Information Using Movable Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A changeable alphanumeric sign with printed characters is disclosed. The sign is universally changeable in the sense that any combination of alphanumeric characters may be displayed by selectively positioning a set of display tapes in each character window. This arrangement minimizes the length of dis-play tapes required. Each tape of a set of tapes is printed on both front and back surfaces with character segments and is connected between a driving roller and a driven roller in a manner to display one front surface segment and one back surface segment at a time. The tape segments which carry the respective character segments are progressively longer from one end of the tape to the other and the set of tape segments which are dis-played together in the window all bear different character segments of the same character so that an entire character is displayed. All tapes in the sat are driven in unison to successively present the character segments of each tape in registry with respective window segments. An open-loop posi-tioning system is used to position all sets of tapes concurrently but independently to change the characters of the sign.
A changeable alphanumeric sign with printed characters is disclosed. The sign is universally changeable in the sense that any combination of alphanumeric characters may be displayed by selectively positioning a set of display tapes in each character window. This arrangement minimizes the length of dis-play tapes required. Each tape of a set of tapes is printed on both front and back surfaces with character segments and is connected between a driving roller and a driven roller in a manner to display one front surface segment and one back surface segment at a time. The tape segments which carry the respective character segments are progressively longer from one end of the tape to the other and the set of tape segments which are dis-played together in the window all bear different character segments of the same character so that an entire character is displayed. All tapes in the sat are driven in unison to successively present the character segments of each tape in registry with respective window segments. An open-loop posi-tioning system is used to position all sets of tapes concurrently but independently to change the characters of the sign.
Description
p-305/6 lO 5'~ 9 6 FIELD OF THE INVENTION
This invention relates to information displays and particularly to such displays as are capable of presenting any of a number of alphanumeric displays.
BACKGROUND OF THE INVENTION
The problem of presenting a readily changeable alpha-numeric readout in a small space has been solved in many different fashions, as exemplified by neon-glow-discharge tubes, liquid crystal readouts, solid-state electroluminescent devices, and the like. Most such arrangements require operating signals which themselves contain most or all of the information to be displayed, and in any case are in general poorly adapted to large scale readouts, such as may be seen readily from a consid-erable distance. Further, a general problem with light-emitting displays is illegibility when the ambient light level is high.
Opaque displays, in contrast, increase in visibility as the ambient light increases.
A need exists for a mechanically sound, readily and quickly changeable and accurate display for such diversified uses as destination indicators for buses, advertising signs, indicators of ambient temperature, time of day, and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a readily changeable display device adapted to displaying letters, numerals, words and phrases and the like within the framework of a mechanically sound apparatus.
Another object of the invention is to provide such a device including positioning means whereby the display may be selectively changed to any desired configuration, and is especially well adapted to positioning by automatic devices, particularly those under computer or machine control.
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P-305/6 ~ 6 A particular application of the subject invention is in the field of destination signs for transit vehicles such as buses and trains. Such destination signs must be changeable according to the particular route of the vehicle and, in modern day transit systems, each sign must be capable of displaying a large number of different destination names in alphanumeric form. A typical destination name may require forty or more characters and the sign must be changeable quickly from one name to another. In the past, destination signs have taken the form of a roller curtain wide enough to accommodate the requisite number of characters and long enough to hold a full set of destination names required for a given vehicle. One great dif-ficulty with this type of destination sign is that the roller curtains must be printed with special destination names according to the route of a particular vehicle or fleet of vehicles. This requires the printing of a large number of different destination signs for a given metropolitan area with attendant high cost.
Furthermore, with long sign curtains, it is difficult and expensive to provide automatic sign changing systems.
The roller curtain destination sign, despite the - above-mentioned difficulties, has an exceedingly important attribute, namely, it affords excellent readability despite wide variations in ambient light. Further, it lends itself to large scale displays so the sign can be read from a distance.
As alluded to above, the roller curtain destination sign in the form of an opaque display, is presently preferred for destina-tion signs over all other known displays.
This invention seeks to take advantage of the read-ability of an opaque display and to overcome the difficulties of the roller curtain destination sign. In general, this is accomplished by a sign having a plurality of window areas - .,:, - -.. . . .
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~05~096 each of which is adapted to display one alphanumeric chara~ at a time on a set of display tapes; each window area is capable of selectively displaying any one set of characters by selectively positioning the respective tapes of the set. Thus, a selected destination name may be displayed by selective positioning of the sets of tapes.
This scheme allows any destination name to be formed and displayed using identical sets of character display tapes for each character window area. Thus, the same set of character display tapes may be produced in multiple copies to make up a destination sign and the same destination sign may be used on any route since any destination name may be formed by the sign.
To make practical this concept of a universal destina-tion sign, this invention provides a broken-character, broken-word arrangement. The broken-character utilizes plural display tapes to form each character rather than a single tape showing all characters in succession; by this technique; each tape is shortened to a fraction of the length of the single tape.
Therefor the wrap-up of the tapes is minimized and the maximum displacement of any tape to form any character is a fraction of that required in the case of a single tape. The broken-word arrangement utilizes the tapes in each set which are only one character wide and which are used for only one window area.
The tapes of each set are positionable independently of the tapes of any other set; this enables the number of character portions disposed along the length of each tape to be kept at an abso}ute minimum (since the tape is only one character wide and no pairs or combinations of character portions are involved laterally). This arrangement allows the sets of tapes to be displaced simultaneously to form their respective characters.
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P-3~5/6 1()5'~96 The invention is realized in a sign having plural window areas each adapted to display a single character with portions of the character allocated to discrete window segments.
Plural sets of display tapes are disposed at respective window areas for collectively forming any character at a time. Each tape has character segments imprinted thereon in a predetermined order at discrete segments of the tape along the length thereof with the number of character segments being equal to the number of characters to be displayed and each character segment cor-responding to that segment which is to occupy the correspondingdiscrete window segment when the character is displayed. Movable support means are provided for supporting each set of tapes so that a selected segment of each tape can be seen at a time in each discrete window segment. A separate clutch means connects each movable support means with a common motor and the clutch means are selectively actuated for concurrently butindependently displacing all sets of display tapes to change the plural character of the sign.
Also, according to this invention, a changeable display of printed alphanumeric characters is provided which faithfully reproduces each character, one at a time with a minimum of translatory motion required in changing from one character to another. In general, this is accomplished by using a set of display tapes with each tape bearing discrete character segments 25 which are imprinted on both front and back surfaces of the tape.
A driving roller is connected with one end of each tape and a driven roller is connected with the other end, and the tape is supported for displaying one surface segment of the front and of the back of each tape in respective segments of each window.
The set of surface segments being displayed together in the , P-305/6 l~)S'~ 9 6 window all bear different character segments of the same character so that an entire character is displayed. Means are provided for displacing the tapes in unison along their length to successively present the character segments in registry with S the respective window segments whereby all characters of the set may be successively displayed. The number of display tapes in the set is equal to one-half the number of character segments.
The length required for each tape varies inversely with the number of segments which is chosen to make up each full character.
Further, in accordance with the invention, faithful reproduction of the characters is provided by means which ensures proper positioning of the character segments within the respective window segments. This is accomplished by placing the character segments on respective surface segments of the tape with the surface segments being progressively longer from one end of the tape to the other to allow for wrap-up of the tape on the rollers. Further, the character segments are nonuniformly spaced along the length of the tape so that equal angular dis-placements of the driving roller causes proper alignment of the character segments in the window segments.
Further, according to the invention, the proper posi-tioning of the character segments is enhanced by relating the roller size to the length of character segments. In particular, the diameter of the rollers should be approximately equal to the length of two character segments.
Further, according to the invention, the display of each character, even though it is a composite of several seg-ments, is produced without distortion. For this purpose the number of character segments is selected so that the horizontal baxs of a character may be carried all on one segment and yet be , . ~ ' -- ' .
-P-305/6 ~ 0~6 properly located in the character format. Preferably, the number of character segments is eight. Additionally, distortion between adjacent segments is minimized by fairing of the character line at the upper and lower extremities of the segments.
Further, according to the invention, the driving and driven rollers are disposed in a minimum of space and may be driven by a single input shaft so the rollers mdve only in unison.
This is accomplished by placing the driving roller of each set behind the display window and the driven roller immediately behind the driving roller with equal size gears on all rollers and meshing with at least one adjacent gear.
DETAILED DESCRIPTION
A more complete understanding of this invention may be obtained from the following description, taken with the accompanying drawings in which:
FIGURE 1 is a front view of three display units in accordance with the invention, each exhibiting a different numeral or figure;
FIGURE 2 is a partially cut-away perspective view of a typical embodiment of the inventive display unit:
FIGURES 3a and 3b are respectively the front and back sides of a display tape such as may be used in the device;
FIGURE 4 is a diagrammatic side view of the device showing the winding mode of the display tape on the rollers;
FIGURE 5 is a sectional view showing the detailed con-struction of a slave roller;
FIGURE 6 is a diagrammatic side view showing the inter-meshing coupling means whereby the driving rollers are rotated and showing an optional positioning code disc;
FIGURE 7 is a top fragmentary view of the code disc shown in FIGURE 6;
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-105'~096 FIGURE 8 shows a destination sign according to this inventiOn î
FIGURE 9 shows a positioning control system for use in this invention;
FIGURE 10 is a diagrammatic showing of the relative positioning of the character segments on the tape;
FIGURE 11 shows a modification of the invention; and FIGURE 12 is a sectional view taken on lines 11-11 of FIGURE 11.
Coming now to FIGURES 2 and 4, it will be seen that the device comprises an array of display rollers, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., which are arranged in spaced pairs, 1,2; 3,4;
etc., and in which two adjacent pairs form groups of four rollers each, such as 1-4 inclusive, 5-8 inclusive, and so forth. Further-more, all of the axes of the cylindrical display rollers 1, 2, 3, etc., are in the same plane so that all of the cylindrical dis -play rollers are tangent to a display plane, the position of this tangent display plane being indicated in the drawings by those segments of the tapes which lie flat on the front of the display device, as shown, for example, in FIGURE 2 by that portion of the uppermost tape lying between the points indicated~as 11,12,13 and 14 It will be apparent from the drawings and in particular from FIGURES 1 and 2 that those portions of the display tapes visible from the outside form an array of essentially horizon-tal segments which may be viewed as a whole, thus for examplein FIGURE 2 displaying the letter "A" made up of eight horizontal segments.
Reverting now to FIGURE 4, this illustrates the fashion in which the tapes are wound on and over their respective rollers Each group of four display rollers, 1-4,5-8,9-12, etc., is backed up by a driving roller 15, 16, 17 and 18, and by a slave roller :. , ;, ~OS'~096 p_305/6 19, 20, 21 and 22, A tape 23 is fastened at one end to the driving roller 15, and after looping over the back of the driving roller is threaded over display rollers 2 and 1 and thence back over driving roller 15 and thence is threaded over display rol-lers 3 and 4 and is finally taken up by slave roller 19, to whichits opposite end is fastened.
It will be observed that in passing over display rol-lers 1 and 2, one face of the tape 23 is exposed to view, where-as when the tape passes over display rollers 3 and 4 the back or reverse side of the same tape is displayed.
It will be further noted that the next unit in the stack comprising display roller 5, 6, 7 and 8, driving roller 16 and slave roller 20, has its own tape 24. The same is true for the remaining units in this stack involving driving rollers 17 and 18, slave rollers 21 and 22, and tapes 25 and 26 respec-tively. Further, proceeding from the top of the stack downward each successive driving roller together with all the rollers actuated thereby rotates in a sense opposite to that of its neighbor next below, for reasons which will appear later.
In the embodiment shown in the drawings, four units are shown in a vertical stack. It will be clear that more or fewer could be used in accordance with the nature of the information to be displayed. Likewise, FIGURE 1 shows three such four-stack arrays in horizontal juxtaposition. This enables the information on each of the three devices to be varied indepen-dently of the others, which in some instances is advantageous, as for example when various numbers or various words are to be shown. Clearly, if for example 20 devices are assembled in a hori~ontal array and if each device can display each of the 26 letters of the alphabet and the ten digits from 0 to 9, then any word of up to 20 letters or any digit up to 1 X 102 - 1 : . , - ^ . , , . . . : - .
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. ': ' ' : ~ ' P-305/6 ios~6 can be displayed at will.
~everting once more to the drawings, the slave rollers 19, 20, 21 and 22 are take-up rollers which serve to wind up, or as the case may be, to unwind the tape when the display is changed, A11 of the driving rollers 15, 16, 17 and 18 and the slave rollers 19, 20, 21 and 22 are geared together as may be seen from FIGURE 6, and because of the relative sense of rotation of the various rollers this may be done in the extra-ordinarily simple fashion shown in FIGURE 6. Thus, all of the gears are meshed together at their points of contact, which leads to a complete avoidance of any slippage problems which might otherwise cause the tapes in a given stack to become out of phase. As a given tape is wound from its driving roller onto its slave roller, or contrariwise, it will be clear that a given amount of angular rotation will correspond to a slightly varying linear payout or uptake because of the finite thickness of the wound tape. We compensate for this slight disparity in the required angular rotation between a given driving roller and its slave roller by providing a spring loading in torque for each slave roller, as may be seen from FIGURE 5. It will be clear from that drawing that the gear 27 does not drive the roller 19 directly and positively but only through the inter-mediary of a helical spring 28, which is set so as to impart a moderate degree of tension in the tape. Spring 28 is engaged at one end to endpiece 29 forming part of the slave roller 19;
whereas at the other end it engages anchor pin 30 which is fixedly attached to the drive shaft 31 which in turn is fixedly attached to gear wheel 27. A stop pin 32 is attached to end-piece 49 of slave roller 19, and serves to limit the rotation of shaft 31 with respect to slave roller 19. It serves to hold the spring 28 from being overstressed during operation if _g_ ;
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'~ ,' . .: . ' ' ' ~,o5~096 the tape or roller should stick. The arrangement of course is repeated for each unit in the stack.
It will be clear from the foregoing and particularly from FIGURE 2, that the array of gears attached to the driving rollers are not only intermeshed with each other, but are also intermeshed with the array of gears which are attached to the slave rollers, and both arrays are intermeshed so that all of the gears may only rotate in unison, taking into account the opposite senses of rotation of adjacent gears. ThuS each driving roller gear engages at least one other driving roller gear as well as its corresponding slave roller gear; and the same may be said for each of the slave roller gears, each one of these engaging at least one other slave roller gear while at the same time engaging its corresponding driving gear.
Turning for the moment to FIGURES 3a and 3b, these show respectively the front and back sides of tape 23, which as will be appreciated from the foregoing explanation has, depending upon the particular setting of the device, a segment of one side displayed between display rollers 1 and 2, and another segment from the other side displayed between the display rollers 3 and 4. FIGURE 1 shows the setting of the de-vice so as to display the letter "A". In FIGURE 3a, that segment forming the top half of the upper one-quarter of the let-ter "A" is indicated by 33; whereas that portion of the reverse of the tape shown on FIGURE 3 b which forms the lower half of the uppermost one-quarter of the letter "A" is indicated by 34.
The tape shown in FIGURES 3a and 3b bears sufficient markings to form the upper one-quarter portion, that is, between rollers 1 and 4, of all 26 letters of the alphabet, all ten digits from 0 through 9, a period (.), a dash (-), a slash (/), and a blank space.
lOS~ 096 p_305/6 It may be remarked that for convenience in explaining our invention we have shown the various rollers as horizontal, with the stacking vertical; but the terms "horizontal" and "vertical" are used mainly for convenience. It is self-evident that the entire apparatus shown may be rotated through 90, so that the rollers will then be vertically disposed. Obvious changes will then have to be made in the arrangement of the subject matter to be displayed, except in the infrequent case that the material consists of symbols having four-fold symmetry such as circles, plus signs, crosses of equal arm length and the 1, 4 and 5 spots on dice and the like.
As already noted, the display is shifted to a new posi-tion by the rotation of any of the driving or slave rollers by one-quarter turn, that is, by 90, for the relative propor-tions of the particular apparatus depicted in the drawings. Of course, it is a simple matter to change the ratio of the dia-meter of the driving and slave rollers to the spacing distance between a single display roller pair so as to vary the amount of rotation required to produce a new setting in the display.
We find the ratios shown and described to be best, however, for it leads to a comfortable amount of working space behind the display rollers. On FIGURE 6, four index marks 45, 46, 47 and 48 are shown on the face of gear 27, and it will be clear from the foregoing that the display can be changed by rotating the driving/slave gear assembly by 90, This may readily be done by hand with the aid of either knob 50 on the face of gear 27 or knob 51 on the face of gear 35. Exact positioning is facilitated by observing the four index markings on the face of gear 27. Remote control of rotation may of course be effected by any of the means well known to those skilled in the art, such as by the use of cables, pulleys and the like.
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, 5;~96 Such repositioning of the display by hand is adequate in many cases where the destination is changed infrequently or where only two or three display devices are used, as in FIGURE 1.
In many other cases, however, it is desirable to be able to reposition the display device automatically. In a destination sign for buses where a large number of characters are displayed, an automatic system is desirable. A destination sign, as shown in FIGURE 8, comprises an enclosure or case 60 which i~
provided with a plurality of windows 62~which display respective alphanumeric characters making up a destination name. A sign module 64 is positioned within the case 60 behind each window 62 so as to present its character display through the window.
A closed-loop positioning system may be employed for automatic selection of the desired character display~ In the device of FIGURES 2 and 4, the uppermost tape 23 bears a coded endstrip 36 in the portion shielded from view. This strip bears positioning markers in an array of parallel channels, the mark-ings consisting of opaque portions in an otherwise transparent or translucent tape. The momentary position of tape 23 is registered by an optical code sensor 38 which may conveniently comprise a light source 37 and a multiple photodiode or like receptor means, none of which requires to be set forth in any detail since this general type of coded positioning sensing and registration is well known in the art. The signal given by sensor 38 is used to actuate a drive motor 39 (see FIGURE 6), which again is a matter of well-known technology. It is of course unnecessary to provide more than one of the display tapes with the coded edge portion since all of the tapes are in effect geared together and move simultaneously as already described.
As is conventional in closed-loop positioning systems, a command signal is applied to the input according to the positioning ,.. " . . . . .
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desired, i.e. according to the character to be displayed~ The command signal causes the drive motor 39 to be energized. The tapes are displaced in unison and the sensor 38 continuously produces a follow-up signal corresponding to the actual posi-tioning of the tapes The follow-up signal is compared with the command signal and when correspondence or equality is achieved, the motor is stopped and the selected character is displayed by the tapes. In a closed-loop system, precise posi-tioning of the tapes may be achieved since the positioning code is applied to the tape itself and may be positionally correlated with the respective character segments distributed along thelength of the tape. While positioning of the tapes by use of a closed-loop positioning system does circumvent certain posi-tioning pxoblems, it is disadvantageous in certain respects.
In paxticular, where two or more modules are to be used together and adapted to display different characters, it isnecessary to use a separate positioning system for each display device. Further, in a closed-loop system a failure in locating the correct positional code signal will result in the display of a wrong or garbled character, or perhaps, damage to the device. As will be discussed below, an open-loop type of posi-tioning system is preferred and the display device of this invention is adapted for such positioning.
For changing the display from one character to another, an open-loop control system is preferred. For this purpose, it is desirable that succeeding characters may be selected by advancing or reversing the tapes through equal increments of angular displacement of the driving rollers.
Th~s will enable two or more display modules to be operated from a single drive motor with individual clutches for each module. However, because the tape is wrapped in varying -~
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lOS'~0~6 amounts on the rollers according to the tape positioning, the effective roller diameter varies and a given angular displace-ment of a roller does not correspond to the same lineal displace-ment of the tape. In the illustrative example, the relative dimensions have been chosen so that the effective diameter of the drivinq roller is such that one-fourth of a revolution forward from its home or reference position will take up a length of the tape equal to the axial length of each window segment.
(In this home position, the effective diameter includes the roller diameter plus any tape leader wound thereon.) Accordingly, the first revolution of the roller will take up the first four character segments. However, during the next revolution the roller will have an effective diameter which is larger by twice the thickness of the tape and will take up a length of tape greater than the next four character segments. The effec-tive diameter of the roller continues to increase with approxi-mately each succeeding group of four character segments. Thus, it can be seen that as the tape is advanced or taken up further on the driving roller, each ninety degree increment of roller rotation will take up slightly more tape than the previous increment. So that equal angular increments of roller dis-placement will provide accurate positioning of successive character segments, the character segments are nonuniformly spaced along the length of tape, as will be described subse-quently.
An open-loop positioning system which is especially adapted for a destination sign is illustrated in FIGURE 9.
Each of the sign modules 64 in this system is the same as that shown in FIGU~E 2 except that the coding strip 36 and sensor 38 are omitted. For the open-loop positioning system, a shaft P-305/6 ~ os~05~6 position encoder 40, as shown in FIGURE 6, is geared to the drive shaft for the display devices. As noted in FIGURE 6, the drive motor 39 drives each display device through a drive gear 41 and also drives an encoder 40 through a pinion gear on the same shaft. The shaft position encoder 40 bears an annular coding strip 42. The coding strip coacts with a light source 43 and an optical sensor 44, as depicted in FIGURE 7, to produce an electrical signal corresponding to the angular position of the driving shaft.
The open-loop positioning system is shown in block diagram in FIGURE 9. The motor 39 is a reversible electric motor and is provided with an elongated drive shaft 66 mechanically coupled with the encoder 40. Each of the display modules 64 is separately coupled with the drive shaft 66 through --a respective clutch 68. A selector means 72 is adapted to produce an electrical signal corresponding to the desired posi-tioning for each of the modules 64. The selector means 72 receives an input signal from the encoder 40 which is indicative of the actual positioning of the motor shaft 66. The encoder 40 also provides a position signal to a motor control means 74 which controls the energization of the motor 39. The output of the selector means 72 is connected with the input of a clutch control means 76 which supplies individual control signals to the respective clutches 68. In operation, the selector means 72 is set acaording to the desired position for each of the display modules~ This setting initiates the energization of the motor 39 through the motor control means 74 which causes the motor to drive all of the display devices in the reverse direction to a home position. The motor is automatically reversed by the motor control means upon reaching the home position and the 1~S,~g6 clutches are selectively engaged and disengaged through the clutch control means 76 so that each display module is positioned according to the setting of the selector means. Thus the display modules 64 are controlled independently and are driven concur-rently from the home position to the respective display positions.
So that equal angular increments of roller displace-ment will provide accurate positioning of successive character segments, the character segments are nonuniformly spaced along the length of the tape. This is depicted in FIGURE 10 which is a diagrammatic representation of tape 23 showing the front sur-face and back surface thereof side-by-side with the respective display window segments therebetween for showing the positional correlation. The front surface of the tape 23 is shown in fragmentary sections on the left side of FIGURE 10 and these sections are enlarged relative to the showing of the front surface in FIGURE 3a. Similarly, the back surface of the tape 23 is shown in enlarged, fragmentary sections on the right side of FIGURE 10. The back surface view in FIGURE 10 shows the tape as it would appear if it were turned side-for-side from the front surface view, i.e. the tape is turned over by rotation about its longitudinal axis. (In FIGURES 3a and 3b, the tape in FIGURE 3b is turned end-for-end from the position shown in FIGURE 3a, i.e. it is turned over by rotation about a transverse axis.) The tape 23 comprises a leader 162 at one end thereof which is secured to the driving roller 15. It also comprises a leader 164 at the other end thereof which is secured to the slave roller 19. The tape 23, between the leaders, comprises a plurality of tape surface segments 166, each of which is of xectangular shape and extends the full width of the tape. The surface segments 166 in a group, A, are of the same length; the , : :
surface segments 166 in successive groups B,C, etc. are progressively longer. The shoxtest surface segments are adjacent the leader 162 and the longest are adjacent the leader 164. The surface segments 166 accommodate the various character segments, such as character segment 3~ which is shown in actual configura-tion in FIGURE 10 and in FIGURE 3a. The other character segments are represented in FIGURE 10 in dummy form by the hatched sections, one of which is superposed upon each of the tape sur-face segments 166. It is noted that each of the character segments is allotted an axial length, C. This length, C, is suitably equal to the axial dimension of the shortest of the tape segments 166. The tape segments in each succeeding group are longer than those in the preceding group by an incremental length, so that an extension 168 is provided for the character segments, as indicated. This extension will vary from zero length for the character segments in the first group (group A) to a maximum length for the character segments in the last group. In practice, the extensions 168 are not left blank; instead, the character configuration is extended through that portion so as to avoid showing a blank line in a character display in case of a positioning error.
FIGURE 10 also depicts the positional relationship of the front and back surfaces of the tape 23 in relation to a viewing window 170. The viewing window is an aperture or area bounded by the sides of the character segments and the top and bottom, respectively, of the uppermost and lowermost character segments. In the device as depicted in FIGURE 2, the window 170 is defined by the opening in the front of the frame of the device. It is noted that in FIGURE 10 the tape 23 is depicted as being laid flat alongside the window 170, whereas, in fact, the tape 23 is disposed within the window and is looped over the l~ls~'~o96 display rollers and partially wound on the driving and slave rollers. The window 170 is divided into plural window segments 172a,172b and so forth, according to the total number of character segments to be displayed at a time. Each window segment has an axial length, L, equal to the axial length, C, of the character segments. It will be understood that the window segments are not separated by physical boundaries, instead, each window segment is an allotment of space from the total window area to a character segment which has the same relative position in the character format as the window segment has in the window area.
In FIGURE 10, the tape 23 is shown in the same position relative to the display window 170 as it is in FIGURE 2, i.e.
the letter A is displayed and the character segment 33 is dis-played in the window segment 172a. The back side of the tape 15 23, as shown in FIGURE 8, is comprised of tape surface segments -166' which are progressively longer, by groups, as described above with reference to the front surface. The character seg-ments are all of the same length and the extensions 168' vary -in the same manner as described above. With the tape 23 in the position for displaying the character A, as described, the character segment 34 is displayed in the window segment 172b.
The remaining segments of the character A will appear in the respective window segments as depicted in FIGURE 2.
In the illustrative embodiment, it is to be noted that ninety degree increments of rotation of the driving rollers will successively present the successive character segments in accurate alignment with the respective window segments.
It will be understood that the relative dimensions of the roller diameter and the character segments may be changed to suit a particular design.
l(~S'~
The tape material is preferably a thin sheet stock which has high tensile strength and which is dimensionally stable under varying ambient temperature and humidity conditions. One preferred material is polyester film such as that sold under the trademark "Mylar" by E.I. du Pont de Nemours of Wilmington, Delaware, Even with a thin tape, the wrap-up of the tape on the roller has a significant effect upon the accurate positioning of the character segments. It has been found that this problem of tape wrap-up is exaggerated by the use of small rollers.
The small roller requires a large increment of roller rotation, as compared to a large roller, for producing a given character segment length. It can be shown that the length of successive tape segments for equal increments of roller rotation varies as the square of the angular increment. Accordingly, a large angular increment which is required for small rollers will result in a large variation in tape segment length and hence there will be inefficient use of the tape due to the unused space ;
between character segments, i.e. the extensions 168 shown in FIGURE 10 and described above. To minimize this effect, it is desirable to use large rollers. Further, the tape thickness will differ somewhat from the design value and this will con- `~
tribute to positioning error. The positioning error due to tape thickness variation will vary with the square of the incremental angle of roller rotation for each character segment and with -the square of the number of character segments. Therefore this error is minimized by the use of a larger roller. It is prefer-red that the roller diameter be made approximately equal to the sum of the distance spanned by two window segments, i.e.
approximately equal to twice the distance between the points of tangency ll and 12 in FIGURE 2. This provides a tape segment l~S~O~;
angle of about ninety degrees or about four tape segments per circumference.
Although an open-loop positioning system is advanta-geous in many respects, it does not provide absolute accuracy in positioning the tapes for the character displays. Accordingly, the foregoing features of character segment spacing and roller diameter are of great importance in producing characters with faithful reproduction, especially where a large number of characters, for example forty or so, are represented in a single module. Additionally, the fidelity of character reproduc-tion is enhanced by proper selection of the number of segmentsper character. The number of segments per character should be selected so that each horizontal bar in a character is provided by one, and only one, character segment; further, such character segment should carry no portion of the character other than the horizontal bar. With this arrangement, the upper and lower edges of the horizontal bar necessarily occur at the cracks between segments. It has been found that this requirement is fulfilled best with eight segments per character because it permits proper relative positioning of the horizontal bars in all characters in all classes or fonts of character styles. It is found that six segments per character does not permit proper placement of the horizontal bars without fragmenting a bar, With parts on two segments; ten segments per character is too many and horizontal bars would have to be fragmented to obtain pxoper placement.
In order to compensate for positioning errors of the charactex segments in displaying a given character, the appear-ance of misalignment is minimized by fairing of the character segments at the upper and lower extremities thereof. This is iOS'~096 illustrated in FIGURE 10 which shows the character segments 33 and 34. In these segments, for example, the character lines at the upper extremities 176 and at the lower extremities 178 are faired toward the vertical direction, i.e. the lines are diverted from the trend line of the character style to approach asymptotically a vertical line. Consequently, when two adjacent character segments are not accurately positioned the appearance of misalignment of the character trend line is minimized.
As described above, the driving rollers 15, 16, 17 and 18 are directly driven by the roller shafts and the slave xollers 19, 20, 21 and 22 are spring driven by the roller shafts to compensate for the disparity in the required angular rotation for linear payout and uptake in transferring tape from one roller to the other. The driving rollers are positioned immediately behind the window segments and the driven rollers are immediately behind the driving rollers. Each pair of driving and slave rollers, being of a diameter approximately equal to two window segments, is accommodated in the space of the projected area of the respective window segments. This enables the module to be of compact design within a rectangular box having a height and width substantially equal to that of the window.
Reverting again to the winding arrangement of the tapes, it is observed that the tape is always held in tension by reason of the spring loading in the slave roller. It is desirable to maintain the tape tension at a value such that it will be stretched tightly across the display rollers but, of course, the spring loading varies with the amount of tape -windup on the driving roller. The spring loading is the smallest when most of the tape is on the slave roller and in this l~S',~:O~
condition the spring torque, working aginst the friction in the tape and roller system, may tend to allow the tape to become somewhat slack across the display rollers. This is overcome in the winding arrangement, as shown in FIGURE 4, by laying the loop of tape from the display rollers directly upon the driving roller. Note that for each set of rollers, the tape passes immediately from the driving roller over a first set of display rollers and thence is looped back over the driving roller in engagement therewith over more than 180 before it is passed over the second set of display rollers to the slave roller.
This causes the driving roller to serve as a feed roller and obviates the need for idler rollers for looping the tape. As a feed roller it tends to keep the tape tight over the display rollers for both directions of rotation of the driving roller.
A modification of the invention is shown in FIGURES 11 and 12. In this embodiment of the invention, the tapes are wound upon and displayed from the surfaces of the driving and slave rollers; the display rollers used in the embodiment of FIGURE 2 are dispensed with. Referring to FIGURES 11 and 12, the display module 80 comprises a frame 82 and plural sets of driving and slave rollers. Each driving roller 84, 85, 86 and 87 is directly connected with its respective shaft and carries a gear 88, 89, 90 and 91 which is fixedly connected therewith.
Each of the slave rollers 92, 93, 94 and 95 is spring loaded in the same manner as slave roller 19 described with reference to FIGURE 5. Each of the slave rollers is connected through a spring loaded shaft with respective gears 96, 97, 98 and 99.
An input gear 101 is manuallly operable by a crank 102 and is meshed directly with gear 97 of the slave roller 93. All of the 30 driving and slave rollers are of the same diameter and all of ~' .. ; . `
P-305/6 l~)S'~O~
the gears, except the input gear 101, are of the same size. It is noted that the rollers are of a diameter approximately equal to a single window segment of the display where a window segment is that portion of the total display area which is allotted to a single character segment. A tape 103 has one end secured to the driving roller 84 and the other end secured to the slave roller 92, the tape being wound between the rollers in an "S" configura-tion. Similarly, a tape 104 is connected between the driving roller 85 and the slave roller 93, the tape 105 is connected between the driving roller 86 and the slave roller 94 and the tape 106 is connected between the driving roller 87 and the slave roller 95. The various characters represented by the module are displayed successively by rotation of the input gear through successive angular increments of equal value.
Although the description of this invention has been given with reference to a particular embodiment, it is not to be construed in a limiting sense, many variations and modifications will now occur to those skilled in the art. For a definition of the invention reference is made to the appended claims.
This invention relates to information displays and particularly to such displays as are capable of presenting any of a number of alphanumeric displays.
BACKGROUND OF THE INVENTION
The problem of presenting a readily changeable alpha-numeric readout in a small space has been solved in many different fashions, as exemplified by neon-glow-discharge tubes, liquid crystal readouts, solid-state electroluminescent devices, and the like. Most such arrangements require operating signals which themselves contain most or all of the information to be displayed, and in any case are in general poorly adapted to large scale readouts, such as may be seen readily from a consid-erable distance. Further, a general problem with light-emitting displays is illegibility when the ambient light level is high.
Opaque displays, in contrast, increase in visibility as the ambient light increases.
A need exists for a mechanically sound, readily and quickly changeable and accurate display for such diversified uses as destination indicators for buses, advertising signs, indicators of ambient temperature, time of day, and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a readily changeable display device adapted to displaying letters, numerals, words and phrases and the like within the framework of a mechanically sound apparatus.
Another object of the invention is to provide such a device including positioning means whereby the display may be selectively changed to any desired configuration, and is especially well adapted to positioning by automatic devices, particularly those under computer or machine control.
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P-305/6 ~ 6 A particular application of the subject invention is in the field of destination signs for transit vehicles such as buses and trains. Such destination signs must be changeable according to the particular route of the vehicle and, in modern day transit systems, each sign must be capable of displaying a large number of different destination names in alphanumeric form. A typical destination name may require forty or more characters and the sign must be changeable quickly from one name to another. In the past, destination signs have taken the form of a roller curtain wide enough to accommodate the requisite number of characters and long enough to hold a full set of destination names required for a given vehicle. One great dif-ficulty with this type of destination sign is that the roller curtains must be printed with special destination names according to the route of a particular vehicle or fleet of vehicles. This requires the printing of a large number of different destination signs for a given metropolitan area with attendant high cost.
Furthermore, with long sign curtains, it is difficult and expensive to provide automatic sign changing systems.
The roller curtain destination sign, despite the - above-mentioned difficulties, has an exceedingly important attribute, namely, it affords excellent readability despite wide variations in ambient light. Further, it lends itself to large scale displays so the sign can be read from a distance.
As alluded to above, the roller curtain destination sign in the form of an opaque display, is presently preferred for destina-tion signs over all other known displays.
This invention seeks to take advantage of the read-ability of an opaque display and to overcome the difficulties of the roller curtain destination sign. In general, this is accomplished by a sign having a plurality of window areas - .,:, - -.. . . .
:
~05~096 each of which is adapted to display one alphanumeric chara~ at a time on a set of display tapes; each window area is capable of selectively displaying any one set of characters by selectively positioning the respective tapes of the set. Thus, a selected destination name may be displayed by selective positioning of the sets of tapes.
This scheme allows any destination name to be formed and displayed using identical sets of character display tapes for each character window area. Thus, the same set of character display tapes may be produced in multiple copies to make up a destination sign and the same destination sign may be used on any route since any destination name may be formed by the sign.
To make practical this concept of a universal destina-tion sign, this invention provides a broken-character, broken-word arrangement. The broken-character utilizes plural display tapes to form each character rather than a single tape showing all characters in succession; by this technique; each tape is shortened to a fraction of the length of the single tape.
Therefor the wrap-up of the tapes is minimized and the maximum displacement of any tape to form any character is a fraction of that required in the case of a single tape. The broken-word arrangement utilizes the tapes in each set which are only one character wide and which are used for only one window area.
The tapes of each set are positionable independently of the tapes of any other set; this enables the number of character portions disposed along the length of each tape to be kept at an abso}ute minimum (since the tape is only one character wide and no pairs or combinations of character portions are involved laterally). This arrangement allows the sets of tapes to be displaced simultaneously to form their respective characters.
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P-3~5/6 1()5'~96 The invention is realized in a sign having plural window areas each adapted to display a single character with portions of the character allocated to discrete window segments.
Plural sets of display tapes are disposed at respective window areas for collectively forming any character at a time. Each tape has character segments imprinted thereon in a predetermined order at discrete segments of the tape along the length thereof with the number of character segments being equal to the number of characters to be displayed and each character segment cor-responding to that segment which is to occupy the correspondingdiscrete window segment when the character is displayed. Movable support means are provided for supporting each set of tapes so that a selected segment of each tape can be seen at a time in each discrete window segment. A separate clutch means connects each movable support means with a common motor and the clutch means are selectively actuated for concurrently butindependently displacing all sets of display tapes to change the plural character of the sign.
Also, according to this invention, a changeable display of printed alphanumeric characters is provided which faithfully reproduces each character, one at a time with a minimum of translatory motion required in changing from one character to another. In general, this is accomplished by using a set of display tapes with each tape bearing discrete character segments 25 which are imprinted on both front and back surfaces of the tape.
A driving roller is connected with one end of each tape and a driven roller is connected with the other end, and the tape is supported for displaying one surface segment of the front and of the back of each tape in respective segments of each window.
The set of surface segments being displayed together in the , P-305/6 l~)S'~ 9 6 window all bear different character segments of the same character so that an entire character is displayed. Means are provided for displacing the tapes in unison along their length to successively present the character segments in registry with S the respective window segments whereby all characters of the set may be successively displayed. The number of display tapes in the set is equal to one-half the number of character segments.
The length required for each tape varies inversely with the number of segments which is chosen to make up each full character.
Further, in accordance with the invention, faithful reproduction of the characters is provided by means which ensures proper positioning of the character segments within the respective window segments. This is accomplished by placing the character segments on respective surface segments of the tape with the surface segments being progressively longer from one end of the tape to the other to allow for wrap-up of the tape on the rollers. Further, the character segments are nonuniformly spaced along the length of the tape so that equal angular dis-placements of the driving roller causes proper alignment of the character segments in the window segments.
Further, according to the invention, the proper posi-tioning of the character segments is enhanced by relating the roller size to the length of character segments. In particular, the diameter of the rollers should be approximately equal to the length of two character segments.
Further, according to the invention, the display of each character, even though it is a composite of several seg-ments, is produced without distortion. For this purpose the number of character segments is selected so that the horizontal baxs of a character may be carried all on one segment and yet be , . ~ ' -- ' .
-P-305/6 ~ 0~6 properly located in the character format. Preferably, the number of character segments is eight. Additionally, distortion between adjacent segments is minimized by fairing of the character line at the upper and lower extremities of the segments.
Further, according to the invention, the driving and driven rollers are disposed in a minimum of space and may be driven by a single input shaft so the rollers mdve only in unison.
This is accomplished by placing the driving roller of each set behind the display window and the driven roller immediately behind the driving roller with equal size gears on all rollers and meshing with at least one adjacent gear.
DETAILED DESCRIPTION
A more complete understanding of this invention may be obtained from the following description, taken with the accompanying drawings in which:
FIGURE 1 is a front view of three display units in accordance with the invention, each exhibiting a different numeral or figure;
FIGURE 2 is a partially cut-away perspective view of a typical embodiment of the inventive display unit:
FIGURES 3a and 3b are respectively the front and back sides of a display tape such as may be used in the device;
FIGURE 4 is a diagrammatic side view of the device showing the winding mode of the display tape on the rollers;
FIGURE 5 is a sectional view showing the detailed con-struction of a slave roller;
FIGURE 6 is a diagrammatic side view showing the inter-meshing coupling means whereby the driving rollers are rotated and showing an optional positioning code disc;
FIGURE 7 is a top fragmentary view of the code disc shown in FIGURE 6;
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-105'~096 FIGURE 8 shows a destination sign according to this inventiOn î
FIGURE 9 shows a positioning control system for use in this invention;
FIGURE 10 is a diagrammatic showing of the relative positioning of the character segments on the tape;
FIGURE 11 shows a modification of the invention; and FIGURE 12 is a sectional view taken on lines 11-11 of FIGURE 11.
Coming now to FIGURES 2 and 4, it will be seen that the device comprises an array of display rollers, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., which are arranged in spaced pairs, 1,2; 3,4;
etc., and in which two adjacent pairs form groups of four rollers each, such as 1-4 inclusive, 5-8 inclusive, and so forth. Further-more, all of the axes of the cylindrical display rollers 1, 2, 3, etc., are in the same plane so that all of the cylindrical dis -play rollers are tangent to a display plane, the position of this tangent display plane being indicated in the drawings by those segments of the tapes which lie flat on the front of the display device, as shown, for example, in FIGURE 2 by that portion of the uppermost tape lying between the points indicated~as 11,12,13 and 14 It will be apparent from the drawings and in particular from FIGURES 1 and 2 that those portions of the display tapes visible from the outside form an array of essentially horizon-tal segments which may be viewed as a whole, thus for examplein FIGURE 2 displaying the letter "A" made up of eight horizontal segments.
Reverting now to FIGURE 4, this illustrates the fashion in which the tapes are wound on and over their respective rollers Each group of four display rollers, 1-4,5-8,9-12, etc., is backed up by a driving roller 15, 16, 17 and 18, and by a slave roller :. , ;, ~OS'~096 p_305/6 19, 20, 21 and 22, A tape 23 is fastened at one end to the driving roller 15, and after looping over the back of the driving roller is threaded over display rollers 2 and 1 and thence back over driving roller 15 and thence is threaded over display rol-lers 3 and 4 and is finally taken up by slave roller 19, to whichits opposite end is fastened.
It will be observed that in passing over display rol-lers 1 and 2, one face of the tape 23 is exposed to view, where-as when the tape passes over display rollers 3 and 4 the back or reverse side of the same tape is displayed.
It will be further noted that the next unit in the stack comprising display roller 5, 6, 7 and 8, driving roller 16 and slave roller 20, has its own tape 24. The same is true for the remaining units in this stack involving driving rollers 17 and 18, slave rollers 21 and 22, and tapes 25 and 26 respec-tively. Further, proceeding from the top of the stack downward each successive driving roller together with all the rollers actuated thereby rotates in a sense opposite to that of its neighbor next below, for reasons which will appear later.
In the embodiment shown in the drawings, four units are shown in a vertical stack. It will be clear that more or fewer could be used in accordance with the nature of the information to be displayed. Likewise, FIGURE 1 shows three such four-stack arrays in horizontal juxtaposition. This enables the information on each of the three devices to be varied indepen-dently of the others, which in some instances is advantageous, as for example when various numbers or various words are to be shown. Clearly, if for example 20 devices are assembled in a hori~ontal array and if each device can display each of the 26 letters of the alphabet and the ten digits from 0 to 9, then any word of up to 20 letters or any digit up to 1 X 102 - 1 : . , - ^ . , , . . . : - .
.;
. ': ' ' : ~ ' P-305/6 ios~6 can be displayed at will.
~everting once more to the drawings, the slave rollers 19, 20, 21 and 22 are take-up rollers which serve to wind up, or as the case may be, to unwind the tape when the display is changed, A11 of the driving rollers 15, 16, 17 and 18 and the slave rollers 19, 20, 21 and 22 are geared together as may be seen from FIGURE 6, and because of the relative sense of rotation of the various rollers this may be done in the extra-ordinarily simple fashion shown in FIGURE 6. Thus, all of the gears are meshed together at their points of contact, which leads to a complete avoidance of any slippage problems which might otherwise cause the tapes in a given stack to become out of phase. As a given tape is wound from its driving roller onto its slave roller, or contrariwise, it will be clear that a given amount of angular rotation will correspond to a slightly varying linear payout or uptake because of the finite thickness of the wound tape. We compensate for this slight disparity in the required angular rotation between a given driving roller and its slave roller by providing a spring loading in torque for each slave roller, as may be seen from FIGURE 5. It will be clear from that drawing that the gear 27 does not drive the roller 19 directly and positively but only through the inter-mediary of a helical spring 28, which is set so as to impart a moderate degree of tension in the tape. Spring 28 is engaged at one end to endpiece 29 forming part of the slave roller 19;
whereas at the other end it engages anchor pin 30 which is fixedly attached to the drive shaft 31 which in turn is fixedly attached to gear wheel 27. A stop pin 32 is attached to end-piece 49 of slave roller 19, and serves to limit the rotation of shaft 31 with respect to slave roller 19. It serves to hold the spring 28 from being overstressed during operation if _g_ ;
^ - ~ . .
'~ ,' . .: . ' ' ' ~,o5~096 the tape or roller should stick. The arrangement of course is repeated for each unit in the stack.
It will be clear from the foregoing and particularly from FIGURE 2, that the array of gears attached to the driving rollers are not only intermeshed with each other, but are also intermeshed with the array of gears which are attached to the slave rollers, and both arrays are intermeshed so that all of the gears may only rotate in unison, taking into account the opposite senses of rotation of adjacent gears. ThuS each driving roller gear engages at least one other driving roller gear as well as its corresponding slave roller gear; and the same may be said for each of the slave roller gears, each one of these engaging at least one other slave roller gear while at the same time engaging its corresponding driving gear.
Turning for the moment to FIGURES 3a and 3b, these show respectively the front and back sides of tape 23, which as will be appreciated from the foregoing explanation has, depending upon the particular setting of the device, a segment of one side displayed between display rollers 1 and 2, and another segment from the other side displayed between the display rollers 3 and 4. FIGURE 1 shows the setting of the de-vice so as to display the letter "A". In FIGURE 3a, that segment forming the top half of the upper one-quarter of the let-ter "A" is indicated by 33; whereas that portion of the reverse of the tape shown on FIGURE 3 b which forms the lower half of the uppermost one-quarter of the letter "A" is indicated by 34.
The tape shown in FIGURES 3a and 3b bears sufficient markings to form the upper one-quarter portion, that is, between rollers 1 and 4, of all 26 letters of the alphabet, all ten digits from 0 through 9, a period (.), a dash (-), a slash (/), and a blank space.
lOS~ 096 p_305/6 It may be remarked that for convenience in explaining our invention we have shown the various rollers as horizontal, with the stacking vertical; but the terms "horizontal" and "vertical" are used mainly for convenience. It is self-evident that the entire apparatus shown may be rotated through 90, so that the rollers will then be vertically disposed. Obvious changes will then have to be made in the arrangement of the subject matter to be displayed, except in the infrequent case that the material consists of symbols having four-fold symmetry such as circles, plus signs, crosses of equal arm length and the 1, 4 and 5 spots on dice and the like.
As already noted, the display is shifted to a new posi-tion by the rotation of any of the driving or slave rollers by one-quarter turn, that is, by 90, for the relative propor-tions of the particular apparatus depicted in the drawings. Of course, it is a simple matter to change the ratio of the dia-meter of the driving and slave rollers to the spacing distance between a single display roller pair so as to vary the amount of rotation required to produce a new setting in the display.
We find the ratios shown and described to be best, however, for it leads to a comfortable amount of working space behind the display rollers. On FIGURE 6, four index marks 45, 46, 47 and 48 are shown on the face of gear 27, and it will be clear from the foregoing that the display can be changed by rotating the driving/slave gear assembly by 90, This may readily be done by hand with the aid of either knob 50 on the face of gear 27 or knob 51 on the face of gear 35. Exact positioning is facilitated by observing the four index markings on the face of gear 27. Remote control of rotation may of course be effected by any of the means well known to those skilled in the art, such as by the use of cables, pulleys and the like.
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, 5;~96 Such repositioning of the display by hand is adequate in many cases where the destination is changed infrequently or where only two or three display devices are used, as in FIGURE 1.
In many other cases, however, it is desirable to be able to reposition the display device automatically. In a destination sign for buses where a large number of characters are displayed, an automatic system is desirable. A destination sign, as shown in FIGURE 8, comprises an enclosure or case 60 which i~
provided with a plurality of windows 62~which display respective alphanumeric characters making up a destination name. A sign module 64 is positioned within the case 60 behind each window 62 so as to present its character display through the window.
A closed-loop positioning system may be employed for automatic selection of the desired character display~ In the device of FIGURES 2 and 4, the uppermost tape 23 bears a coded endstrip 36 in the portion shielded from view. This strip bears positioning markers in an array of parallel channels, the mark-ings consisting of opaque portions in an otherwise transparent or translucent tape. The momentary position of tape 23 is registered by an optical code sensor 38 which may conveniently comprise a light source 37 and a multiple photodiode or like receptor means, none of which requires to be set forth in any detail since this general type of coded positioning sensing and registration is well known in the art. The signal given by sensor 38 is used to actuate a drive motor 39 (see FIGURE 6), which again is a matter of well-known technology. It is of course unnecessary to provide more than one of the display tapes with the coded edge portion since all of the tapes are in effect geared together and move simultaneously as already described.
As is conventional in closed-loop positioning systems, a command signal is applied to the input according to the positioning ,.. " . . . . .
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P-30s/6 ~Q5'~~
desired, i.e. according to the character to be displayed~ The command signal causes the drive motor 39 to be energized. The tapes are displaced in unison and the sensor 38 continuously produces a follow-up signal corresponding to the actual posi-tioning of the tapes The follow-up signal is compared with the command signal and when correspondence or equality is achieved, the motor is stopped and the selected character is displayed by the tapes. In a closed-loop system, precise posi-tioning of the tapes may be achieved since the positioning code is applied to the tape itself and may be positionally correlated with the respective character segments distributed along thelength of the tape. While positioning of the tapes by use of a closed-loop positioning system does circumvent certain posi-tioning pxoblems, it is disadvantageous in certain respects.
In paxticular, where two or more modules are to be used together and adapted to display different characters, it isnecessary to use a separate positioning system for each display device. Further, in a closed-loop system a failure in locating the correct positional code signal will result in the display of a wrong or garbled character, or perhaps, damage to the device. As will be discussed below, an open-loop type of posi-tioning system is preferred and the display device of this invention is adapted for such positioning.
For changing the display from one character to another, an open-loop control system is preferred. For this purpose, it is desirable that succeeding characters may be selected by advancing or reversing the tapes through equal increments of angular displacement of the driving rollers.
Th~s will enable two or more display modules to be operated from a single drive motor with individual clutches for each module. However, because the tape is wrapped in varying -~
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lOS'~0~6 amounts on the rollers according to the tape positioning, the effective roller diameter varies and a given angular displace-ment of a roller does not correspond to the same lineal displace-ment of the tape. In the illustrative example, the relative dimensions have been chosen so that the effective diameter of the drivinq roller is such that one-fourth of a revolution forward from its home or reference position will take up a length of the tape equal to the axial length of each window segment.
(In this home position, the effective diameter includes the roller diameter plus any tape leader wound thereon.) Accordingly, the first revolution of the roller will take up the first four character segments. However, during the next revolution the roller will have an effective diameter which is larger by twice the thickness of the tape and will take up a length of tape greater than the next four character segments. The effec-tive diameter of the roller continues to increase with approxi-mately each succeeding group of four character segments. Thus, it can be seen that as the tape is advanced or taken up further on the driving roller, each ninety degree increment of roller rotation will take up slightly more tape than the previous increment. So that equal angular increments of roller dis-placement will provide accurate positioning of successive character segments, the character segments are nonuniformly spaced along the length of tape, as will be described subse-quently.
An open-loop positioning system which is especially adapted for a destination sign is illustrated in FIGURE 9.
Each of the sign modules 64 in this system is the same as that shown in FIGU~E 2 except that the coding strip 36 and sensor 38 are omitted. For the open-loop positioning system, a shaft P-305/6 ~ os~05~6 position encoder 40, as shown in FIGURE 6, is geared to the drive shaft for the display devices. As noted in FIGURE 6, the drive motor 39 drives each display device through a drive gear 41 and also drives an encoder 40 through a pinion gear on the same shaft. The shaft position encoder 40 bears an annular coding strip 42. The coding strip coacts with a light source 43 and an optical sensor 44, as depicted in FIGURE 7, to produce an electrical signal corresponding to the angular position of the driving shaft.
The open-loop positioning system is shown in block diagram in FIGURE 9. The motor 39 is a reversible electric motor and is provided with an elongated drive shaft 66 mechanically coupled with the encoder 40. Each of the display modules 64 is separately coupled with the drive shaft 66 through --a respective clutch 68. A selector means 72 is adapted to produce an electrical signal corresponding to the desired posi-tioning for each of the modules 64. The selector means 72 receives an input signal from the encoder 40 which is indicative of the actual positioning of the motor shaft 66. The encoder 40 also provides a position signal to a motor control means 74 which controls the energization of the motor 39. The output of the selector means 72 is connected with the input of a clutch control means 76 which supplies individual control signals to the respective clutches 68. In operation, the selector means 72 is set acaording to the desired position for each of the display modules~ This setting initiates the energization of the motor 39 through the motor control means 74 which causes the motor to drive all of the display devices in the reverse direction to a home position. The motor is automatically reversed by the motor control means upon reaching the home position and the 1~S,~g6 clutches are selectively engaged and disengaged through the clutch control means 76 so that each display module is positioned according to the setting of the selector means. Thus the display modules 64 are controlled independently and are driven concur-rently from the home position to the respective display positions.
So that equal angular increments of roller displace-ment will provide accurate positioning of successive character segments, the character segments are nonuniformly spaced along the length of the tape. This is depicted in FIGURE 10 which is a diagrammatic representation of tape 23 showing the front sur-face and back surface thereof side-by-side with the respective display window segments therebetween for showing the positional correlation. The front surface of the tape 23 is shown in fragmentary sections on the left side of FIGURE 10 and these sections are enlarged relative to the showing of the front surface in FIGURE 3a. Similarly, the back surface of the tape 23 is shown in enlarged, fragmentary sections on the right side of FIGURE 10. The back surface view in FIGURE 10 shows the tape as it would appear if it were turned side-for-side from the front surface view, i.e. the tape is turned over by rotation about its longitudinal axis. (In FIGURES 3a and 3b, the tape in FIGURE 3b is turned end-for-end from the position shown in FIGURE 3a, i.e. it is turned over by rotation about a transverse axis.) The tape 23 comprises a leader 162 at one end thereof which is secured to the driving roller 15. It also comprises a leader 164 at the other end thereof which is secured to the slave roller 19. The tape 23, between the leaders, comprises a plurality of tape surface segments 166, each of which is of xectangular shape and extends the full width of the tape. The surface segments 166 in a group, A, are of the same length; the , : :
surface segments 166 in successive groups B,C, etc. are progressively longer. The shoxtest surface segments are adjacent the leader 162 and the longest are adjacent the leader 164. The surface segments 166 accommodate the various character segments, such as character segment 3~ which is shown in actual configura-tion in FIGURE 10 and in FIGURE 3a. The other character segments are represented in FIGURE 10 in dummy form by the hatched sections, one of which is superposed upon each of the tape sur-face segments 166. It is noted that each of the character segments is allotted an axial length, C. This length, C, is suitably equal to the axial dimension of the shortest of the tape segments 166. The tape segments in each succeeding group are longer than those in the preceding group by an incremental length, so that an extension 168 is provided for the character segments, as indicated. This extension will vary from zero length for the character segments in the first group (group A) to a maximum length for the character segments in the last group. In practice, the extensions 168 are not left blank; instead, the character configuration is extended through that portion so as to avoid showing a blank line in a character display in case of a positioning error.
FIGURE 10 also depicts the positional relationship of the front and back surfaces of the tape 23 in relation to a viewing window 170. The viewing window is an aperture or area bounded by the sides of the character segments and the top and bottom, respectively, of the uppermost and lowermost character segments. In the device as depicted in FIGURE 2, the window 170 is defined by the opening in the front of the frame of the device. It is noted that in FIGURE 10 the tape 23 is depicted as being laid flat alongside the window 170, whereas, in fact, the tape 23 is disposed within the window and is looped over the l~ls~'~o96 display rollers and partially wound on the driving and slave rollers. The window 170 is divided into plural window segments 172a,172b and so forth, according to the total number of character segments to be displayed at a time. Each window segment has an axial length, L, equal to the axial length, C, of the character segments. It will be understood that the window segments are not separated by physical boundaries, instead, each window segment is an allotment of space from the total window area to a character segment which has the same relative position in the character format as the window segment has in the window area.
In FIGURE 10, the tape 23 is shown in the same position relative to the display window 170 as it is in FIGURE 2, i.e.
the letter A is displayed and the character segment 33 is dis-played in the window segment 172a. The back side of the tape 15 23, as shown in FIGURE 8, is comprised of tape surface segments -166' which are progressively longer, by groups, as described above with reference to the front surface. The character seg-ments are all of the same length and the extensions 168' vary -in the same manner as described above. With the tape 23 in the position for displaying the character A, as described, the character segment 34 is displayed in the window segment 172b.
The remaining segments of the character A will appear in the respective window segments as depicted in FIGURE 2.
In the illustrative embodiment, it is to be noted that ninety degree increments of rotation of the driving rollers will successively present the successive character segments in accurate alignment with the respective window segments.
It will be understood that the relative dimensions of the roller diameter and the character segments may be changed to suit a particular design.
l(~S'~
The tape material is preferably a thin sheet stock which has high tensile strength and which is dimensionally stable under varying ambient temperature and humidity conditions. One preferred material is polyester film such as that sold under the trademark "Mylar" by E.I. du Pont de Nemours of Wilmington, Delaware, Even with a thin tape, the wrap-up of the tape on the roller has a significant effect upon the accurate positioning of the character segments. It has been found that this problem of tape wrap-up is exaggerated by the use of small rollers.
The small roller requires a large increment of roller rotation, as compared to a large roller, for producing a given character segment length. It can be shown that the length of successive tape segments for equal increments of roller rotation varies as the square of the angular increment. Accordingly, a large angular increment which is required for small rollers will result in a large variation in tape segment length and hence there will be inefficient use of the tape due to the unused space ;
between character segments, i.e. the extensions 168 shown in FIGURE 10 and described above. To minimize this effect, it is desirable to use large rollers. Further, the tape thickness will differ somewhat from the design value and this will con- `~
tribute to positioning error. The positioning error due to tape thickness variation will vary with the square of the incremental angle of roller rotation for each character segment and with -the square of the number of character segments. Therefore this error is minimized by the use of a larger roller. It is prefer-red that the roller diameter be made approximately equal to the sum of the distance spanned by two window segments, i.e.
approximately equal to twice the distance between the points of tangency ll and 12 in FIGURE 2. This provides a tape segment l~S~O~;
angle of about ninety degrees or about four tape segments per circumference.
Although an open-loop positioning system is advanta-geous in many respects, it does not provide absolute accuracy in positioning the tapes for the character displays. Accordingly, the foregoing features of character segment spacing and roller diameter are of great importance in producing characters with faithful reproduction, especially where a large number of characters, for example forty or so, are represented in a single module. Additionally, the fidelity of character reproduc-tion is enhanced by proper selection of the number of segmentsper character. The number of segments per character should be selected so that each horizontal bar in a character is provided by one, and only one, character segment; further, such character segment should carry no portion of the character other than the horizontal bar. With this arrangement, the upper and lower edges of the horizontal bar necessarily occur at the cracks between segments. It has been found that this requirement is fulfilled best with eight segments per character because it permits proper relative positioning of the horizontal bars in all characters in all classes or fonts of character styles. It is found that six segments per character does not permit proper placement of the horizontal bars without fragmenting a bar, With parts on two segments; ten segments per character is too many and horizontal bars would have to be fragmented to obtain pxoper placement.
In order to compensate for positioning errors of the charactex segments in displaying a given character, the appear-ance of misalignment is minimized by fairing of the character segments at the upper and lower extremities thereof. This is iOS'~096 illustrated in FIGURE 10 which shows the character segments 33 and 34. In these segments, for example, the character lines at the upper extremities 176 and at the lower extremities 178 are faired toward the vertical direction, i.e. the lines are diverted from the trend line of the character style to approach asymptotically a vertical line. Consequently, when two adjacent character segments are not accurately positioned the appearance of misalignment of the character trend line is minimized.
As described above, the driving rollers 15, 16, 17 and 18 are directly driven by the roller shafts and the slave xollers 19, 20, 21 and 22 are spring driven by the roller shafts to compensate for the disparity in the required angular rotation for linear payout and uptake in transferring tape from one roller to the other. The driving rollers are positioned immediately behind the window segments and the driven rollers are immediately behind the driving rollers. Each pair of driving and slave rollers, being of a diameter approximately equal to two window segments, is accommodated in the space of the projected area of the respective window segments. This enables the module to be of compact design within a rectangular box having a height and width substantially equal to that of the window.
Reverting again to the winding arrangement of the tapes, it is observed that the tape is always held in tension by reason of the spring loading in the slave roller. It is desirable to maintain the tape tension at a value such that it will be stretched tightly across the display rollers but, of course, the spring loading varies with the amount of tape -windup on the driving roller. The spring loading is the smallest when most of the tape is on the slave roller and in this l~S',~:O~
condition the spring torque, working aginst the friction in the tape and roller system, may tend to allow the tape to become somewhat slack across the display rollers. This is overcome in the winding arrangement, as shown in FIGURE 4, by laying the loop of tape from the display rollers directly upon the driving roller. Note that for each set of rollers, the tape passes immediately from the driving roller over a first set of display rollers and thence is looped back over the driving roller in engagement therewith over more than 180 before it is passed over the second set of display rollers to the slave roller.
This causes the driving roller to serve as a feed roller and obviates the need for idler rollers for looping the tape. As a feed roller it tends to keep the tape tight over the display rollers for both directions of rotation of the driving roller.
A modification of the invention is shown in FIGURES 11 and 12. In this embodiment of the invention, the tapes are wound upon and displayed from the surfaces of the driving and slave rollers; the display rollers used in the embodiment of FIGURE 2 are dispensed with. Referring to FIGURES 11 and 12, the display module 80 comprises a frame 82 and plural sets of driving and slave rollers. Each driving roller 84, 85, 86 and 87 is directly connected with its respective shaft and carries a gear 88, 89, 90 and 91 which is fixedly connected therewith.
Each of the slave rollers 92, 93, 94 and 95 is spring loaded in the same manner as slave roller 19 described with reference to FIGURE 5. Each of the slave rollers is connected through a spring loaded shaft with respective gears 96, 97, 98 and 99.
An input gear 101 is manuallly operable by a crank 102 and is meshed directly with gear 97 of the slave roller 93. All of the 30 driving and slave rollers are of the same diameter and all of ~' .. ; . `
P-305/6 l~)S'~O~
the gears, except the input gear 101, are of the same size. It is noted that the rollers are of a diameter approximately equal to a single window segment of the display where a window segment is that portion of the total display area which is allotted to a single character segment. A tape 103 has one end secured to the driving roller 84 and the other end secured to the slave roller 92, the tape being wound between the rollers in an "S" configura-tion. Similarly, a tape 104 is connected between the driving roller 85 and the slave roller 93, the tape 105 is connected between the driving roller 86 and the slave roller 94 and the tape 106 is connected between the driving roller 87 and the slave roller 95. The various characters represented by the module are displayed successively by rotation of the input gear through successive angular increments of equal value.
Although the description of this invention has been given with reference to a particular embodiment, it is not to be construed in a limiting sense, many variations and modifications will now occur to those skilled in the art. For a definition of the invention reference is made to the appended claims.
Claims (6)
1. A changeable sign formed of plural alphanumeric characters, said sign comprising: plural window areas each adapted to display only a single character with discrete segments of the character allocated to discrete window segments of the window area, plural sets of display tapes, one set of display tapes being disposed at one of said window areas for collectively forming any of said characters one at a time, each tape having character segments imprinted thereon in a predetermined order at discrete parts of the tape along the length thereof, the number of character segments corresponding to the number of characters to be displayed and each segment correpsonding to that portion of a character which is to occupy the corresponding discrete window segment when the character is displayed, movable support means for supporting each set of tapes so that only one of said tape segments can be seen at a time at each discrete window segment, with all segments of a selected character dis-played together in the respective window area, a motor, a separate clutch means connected between said motor and the movable support means of each set of display tapes, and means for selectively actuating said clutch means for concurrently but independently displacing all sets of display tapes to change the characters of the sign.
2. The invention as defined in claim 1 wherein each tape has character portions imprinted on both surfaces and said support means for supporting each tape includes a first set of rollers for displaying one surface of the tape and second set of rollers for displaying the other surface of the tape.
3. The invention as defined in claim 1 wherein said movable support means for supporting each set of tapes includes a driving roller and a slave roller for each tape with one end of the tape attached to the driving roller and the other end of the tape attached to the slave roller, the clutch means associated with a set of display tapes being connected with one of said rollers, and means coupling the rollers of one tape in a set to the rollers of the other tapes in the same set for rotation in unison.
4. The invention as defined in claim 3 wherein each tape has character portions imprinted on both surfaces and the number of character portions is equal to twice the number of characters to be displayed.
5. The invention as defined in claim 4 including a group of display rollers for each tape in a set having their axes all in one plane whereby a tangent plane to said rollers defines a display plane, each group including two spaced pairs of rollers, the driving roller and the slave roller of the tape being disposed behind the group of display rollers and parallel thereto, said display tape extending from said driving roller and thence over the first pair of display rollers; back over said driving roller and thence over the second pair of display rollers and thence finally to said slave roller.
6. The invention as defined in claim 5 wherein said means coupling the rollers comprises a first array of gears, each of which is attached to one of said driving rollers and a second array of gears, each of which is attached to one of said slave rollers, each of said driving roller gears engaging at least one other driving roller gear as well as its corre-sponding slave roller gear, and each of said slave roller gear engaging at least one other slave roller gear whereby both arrays of gears rotate only in unison.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA316,422A CA1073204A (en) | 1975-12-03 | 1978-11-17 | Changeable printed alphanumeric display system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/637,433 US4064503A (en) | 1975-02-03 | 1975-12-03 | Changeable printed alphanumeric display module |
| US05/637,434 US4067006A (en) | 1975-02-03 | 1975-12-03 | Changeable alphanumeric sign with opaque tape display forming segmented characters and words |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052096A true CA1052096A (en) | 1979-04-10 |
Family
ID=27092833
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,005A Expired CA1052096A (en) | 1975-12-03 | 1976-02-04 | Changeable printed alphanumeric display system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1052096A (en) |
-
1976
- 1976-02-04 CA CA245,005A patent/CA1052096A/en not_active Expired
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