CA1209288A - Information display devices - Google Patents

Abstract

ABSTRACT
Improvements to Information Display Devices A display device of the matrix type utilises coincident current selection of display elements by the provision of row conductors (R) activating row electro-magnets (D) and column conductors (C) activating column electromagnets (H). Each display element includes a rotatable vane (S) which is stable in open and closed positions and a permanent magnet (M) co-operates with the electromagnet (D) to urge the vane (S) into the appropriate position.
Bar (L) extending from the vane (S) contacts the pole face of electromagnets (H) which, when activated, serves to inhibit movement of the vane irrespective of activation of the row electromagnet (D). Thus by pulsing the display row-by-row, the state of the display elements can be set by selective inhibiting of movement in coincident manner of the appropriate vanes (S) by pulsing the respective column conductors.

Description

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mprovemen ~s to Information Dis.play Devic es This itl~rention relates to informatio~ display de~rices of the type in which each displ~y element in the eomplete display ineludes a mov~ble m~mber and an olee~ro~a~net for ~etuatin$ it.
Displays Or thi.s type inel~de those descri~ed i~1J~Sc Patent N~s~ 3,33~ and 3,140,553 which s~c~fie~ rel~.te to diqDlays includin~ a ~t~iY. of displ~y element~.
A~other known displ~y matrix u~iJns ~ techn~que 10 knv~n ~s Go~ ncident Current saleetion i5 deseribed in U.S~ ~ate~t No. 3,469,Z~80 With this arr~ngemer~t, th~re provided a single winding eondue~or for ~aeh ro~ o~
~he la~trix and similarly one for eaeh eolum~. Writi~lg on ~e m~ltrix ean be e~rried ou* row-by~row or eol~mn-15 b~col~lnO l~ith ro-~-by-row ~riting, for examp3.e, each ~ row ~o~ductor i5 energised in turn to seleet. the row~
a)~d coi~eiden~l.ly seleeted column eonductors ~re c~l~er$1sed, corresF)onding t~3 the required p;~ttern o~ dot~3 t:o be written onto the row., Since only onf~ row is ~0 ~ncrgised at ~ time, the main drive power for altering t;he display ele;~lents i~; in the column drives~ For Dl~ny patterns, zll or n~rly all the column~; rnu.s~ b~ g dri~ren sin!ultaneouc;l~,-. .Ln the nrr~ng~ ent in U. S. I7aten No. 3~1~69,2~;, e~ch culllmn conductor mu~t be driYen ~o a~
.5 ~o a~pl.y to ^ach c~f i1;~ ~isoci2ts~1 di~lay ~lem~nt~

,f, , 1209Z88 _ 2 -half of the power needed to alter the state of the displayelement. The arrangment actuates each display elcmcnt ~y the use of ~n individual electromagnet havin~ a core of square loop magnetic material that is permanently magnet-isable. It therefore requires a large~mount of power toactuate the matrix, since for a change of element state, the magnetisation must be reversed along the square hysteresis loop.
An object of the present invention is to reduce the numbe. and total cost of the drive circuits required to energise the electroma~nets. Another object is to provide a simple, low-cost scheme for winding the electro-magnets. A further object is to reduce the pawer required to artuate the display.
The present invention provides a display device inc~luding a plurality of display eleMents, each d.isplay ~l~ment including a member movable bet~een first and second positions in which said display element presents contrastin~g appearances, first electromagnet means havi.ng a core of ferromagnetic material and being arranged to urge sai~ me~ber to move from one to the other of said positions, and second electroma~net means having a core of ~erromagnetic material and being arranged to inhibit movement of said member between said positions urged by ~5 said L irst electromagnet means, ~Y~ereby said display ~loments may be selectively set by activatintr their correspondi.ng first electromagnet means and simultaneously ~ctivatillg particular ones of their corresponding second.
~lcctromagnet mcans so as to allow movement of on].
sele~ted menbcrs.
. l`he preferred cmbodiment of the invention has thc a~vanta6e that the electroma~net for actuating the clis-play elcment nses a corc of so~t ferroma-gnetic nlaterial and req~lires lcss than a quartcr of thc power t.hat wo~lld otherlYise be nceded if it wcre o~ squaro loo~
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~ZC19~288 material. This is beeause the permeability of the soft cor-e material is apprecia~ly grea~er than that of the square loop m~terial, resultin~ in less ampere-t,urns being needed to produee the same magnetic flux. Also the ~rive power applied through a column conductor to each of its display elements can, with suitable desi6n, be made less thzn one fifteenth of the power needed to alter the state of the display elemerlt. Taking -the two factors into account, the colwnn drive power is reduced by a faetor of 30 compared to the previous - arrangement described in U.S. Patent No. 3, 469,~58.
The very low column drive power re~uirement is aehieved ..
in the.preferred enl.bodiment by using a simple ~ut very sensiti.ve inhi.bitor arrangement in each display element, aetuated by the column current.
Another advantage of the pre~erred embodiment of the present invention compared to the arran~ement or U~S. Patent No. 3,469,258 is that only the row cu~rents - have to be bidirectional, instearl o~botl the row and

2~ co~umn currents. There is there~ore a considerable.
savillg in the number of switching circuits, as well as in their power handling requirements. Yet another I advantage of the present arrangement is that~ unlike the arrangement.o~ U.S. Pater~t No. 3,469,25~, the 25 atnplitudes of the row and eolumn currents can be consicler-ably larger than their nominal design values ~ithout resulting in misoperation. This makes the display less ~ . sensitive to the net effects of chan~es itl power suppl;
vo].tage, changes of coil resistance due to temperature

3 variati.ons, and variations oF charac.teristics due to manufacturirlg tolerances.
U.S. Patent Nos. 3,775,881 and 3,56~,938 describe other display matrices with coincidetlt c--rrent selection.
These require much more power than do matrices accorcling 3S to the pr~sen~ inYelltion, partly because they lack cl rctt~omagnel; COI'CS for gui.ding flu~ from l;he windi ngrs ... to t~e dispiay elar.ent; armatures. Tllcy also ;` ', 9Z~8 .~ -- ha~ the ~isadY~nta~e tha~ the arra~ of ~isplay elcments ig buriod wit~3in the ~inding~ making acces~ to the di~pla~r element~ for ma~ntenance difficulto Becau~e of the reduction of column power, the 5 pre~ent invention enable~ matrices to be con~truct~d havin$ 30 tir.~es more row~ without increasing the cost of col~m dri~ers relative to known arra~gements. 'rhis facilit&tes the economical construction of large di~play matrices capable of displaying pict~es with f~n~ dctail.
In order that the pre~ent in~ention may be more readily understood, embodiment~ the~eof ~ill now be described, by way of e~ample, with reference to the accompanying drawing~, in which:-- Fi~ure 1 shows a front perspective view of ~5 part of a matrix di~lay in accordance wit~ one embodi-ment of the in~ention;
F`i~ure 2 shows the wiring scheme of the coil9 o~ the d~splay shown in Fi~ure 1; ~ ¦
I~`igure 3 5how~ adJacent display elemellts of a second embodiment of the invention;
Fi~ure 4 shows a man~er of a~sembly of a display ele~lent part;
~ igure 5 shows a modifica~ion of tho dls~lay sl~ment part sXown i~ ~igure 4; and .~ 2~ ~igure 6 shows one display ~lemen~ ~f a fl~ther ~mbodim~nt of the invcntion.
'~ofcrrin~ to ~igure 1, thero is sho~n a por*ion of a di~play matrix, the portion ha~ing two row~
~nd two columns of display ¢lements. Associated with c~ch row th~re is a ro~ conductor ~ ~nd wi*h each colu~.n ~ co~umn conductor C. The~c desi~nations ar~ follo~cd by a llwnbcr to -indicate the ro~ ar.d col~nn positions.
The display elemcr~ts ~hara a co~nmon opaque basc platc 1 h~vins apertures A therein and are optically of the ty~c dc~cr~bed in U~S~ Patent No. ~,163,33~ from ~hich further . _ .- . , " . .
~ 5 -constructional detail3 may be derived. Ench clcme~t includea a ~ane S mounted with the aid of hingo br~clcets ~ nttaehed to base plate 1 to rotate a~out a horizont~l axi~ bet~een a first stable position in whicn ~t co~ers aperture ~ and a second p~sition in which it unco~ers the aperture, for example qo as tv allow ligh~
from ~ sourco, not shown, behind panel 1 to p23~ ~hrough to the viewer, as iilu~tr~ted for vane S12 in row 1, colwnn ~. Alternati~-ely, or in addition to the light - ~0 so~ce~ the opposite faces of each vane may pre.sont contrasting ~ppearancesl such as di~erent colours.
Each Yane S carries a per~anent magnet M ha~ing a magnctic axi~ normal to t~e plane of the vane and a bar L o~ ~agnet~c material of low remanen~e protl-uding vut ~5 bcyond an ed~e of the Yane. Each display element also includes a first electroma~net pole D placed n~ar to the z~n~ of the masnet M and a second electromagnet pole ~1 ~nounted so AS *0 be in contaot wi*~ or ~er~ close tG the tip of *he protrudin~ portion of bar L, ~hen tl~e ~ane coYers the apert~r~. The polarity of magnet M is chosen go that when pole D is energised by current in *he direc~ion of arrow E, the ~an~ is ur~ed into the aperture co~rerinS ,po~i ~ion O
A~ -~hown in Figure 2, for e~ch row, cQnductor 25 n 3.S wound round each pole D in the row in tu~n a~.d, ~or ~ach column, conductor C iq wound round each pole ~ in . . .
the cvlumn ln turn.
~ method of operatin~ this matrix is as follos~s;
Firstly~ the matrix is blanked by pulsing all rows ~
~0 si~ultaneou31.y ~ith currcnts in the direction of arrow E. The apcrturc~ are thu~ all ~overed. Ne~t, each row coll~uctor ~ in turn is pulsed wi~h currel-t in thc directio~
rrow W0 ~t tho sallle time as a row conductor is ~ul.~ed~ col~L~n collductor3 C are ul~ed for tho.~e cDll~nn ~oxi~i~n~ s~ ere it i~ rc~uiled that tha dis~lay ele~o~t~
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in thc ro~.rem~in ~ight blockins. 1`he ef~ect of pulsing a row conductor ~l in the direction of arrow W i5 to urge the Yanes S into t21e aperture expo~inS position~ l The ourrent in each s¢lected colum~ conductor C is 3 5 made sufficiently large to ensuro that the ~anc S is hold clo~ed ~ith a torque $rcater than that incluced in the vane by energising it~ electromagl1et D.
With the arrangement in ~igure 1, suppression of rotation of vane~ S is possible for both blanking ~ - 10 and writing, since for both Yane positions bar elemellt 1 is in cont~ct with a pole H. This f~ature is use~
.under certain conditions, for example when the m~trix is u~ed to ShO~J the time of day digitally. In this case . those digits that chan~e ~rom minute to minute are bla~ed 15 prior to updatin$ the time. The remaining disits are ;3 left undisturbed. ,i~
Figure 3 illustrates how the arrangelnen* o~ ! i Fl$ure 1 can be modified so that po~es H can hold the ?
. . ~anos only when they~ are in the aperture ~o~ering .0 positior.. The holding po7es H for ~acn row are ~laced ', lower than half way between thc hinge axis of the row ! j ~nd that of the next row down~ and bar L i9 plao~d on th~ ¦Z~
~ane S so that it p.rotrucl~s sideways~ With the Yane in ll, the aperture exposin$ position, bar ~ is spaced away !:
aS ro~n pole H. With thi.s modified arrnt1sement, it is ` ` possible ~o ~lank the matrix row b~ row and to write on ¦~
ench row, i.e. expo~o selected a~ertt~es, as the ro~
l)elo-~ it is being blankedO 1', Xn the ~rrangem~nt~ of Fisuros ~ and 3~ bar li L i~ preferably arranged so thzt its portion that come~
in contac~ with pol~ ~ is free t~ ~lo~e to a limited ¦
ox~ent rclAtive to the v~lle S in.a dileetion n~rmal to tha~ of the ~an~ surf~ce. This 1~ to onsure that when ~h~ Y~no is in tllc ape;-t~rc bloclcin~ po~ition i.t iY in ~5 c~n'cact ~t i i,s top ~i-tl~ so plate 1 ~nd nt t;hc ~ e, timo bar L i~ contact with pole ll, rogardless ~f 3m~11 ri~tions in tho dimensions of the part~. A w~y of achieving the desir~d limit~d de~rec of movement 1 llluatrated in Figure 4, whic}l is n croa-~ ~ectiDnal vi~-~
of a portion of Yane S w~th th~ ~ection talcen thrvughthe longitudinal axi~ of bar L. Holes Q are provided ~n valle S, Bar L is initially U-shaped as indic~ted by the dotted lines and ~s lnserted through hole~ Q prior to bending in the direct~ons indicnted b~- a~rows Z. The ~ 10 lengths of the short portions aliding in apertur2s Q
are chosen to give the de~ired freedotn of motion.
Fis~e 5 shows a modificd arrangement o~ bar L in which the e~d portion T is bifurGatedO Because of the ~005~ mountin~ of bar L through holes Q, bar L i~
~5 free ~o rotnte slightly about its longitudinal axis.
Thus, a small portion of grit lodged betweell one of th~
pron~s of end portiQn T and the face of po~e H will not preYent contact between bar L and pole H~ a.q the other prong is *ree to comc 'nto ~ontact.
Fig~re 6 5how~ another arrangem~nt of ~ane S
and holding bar L~ Bar L i~ pre~sed out of soft iron $
or nickel-iron perm~lloy and is form~d to havc t~o bearin~ ¦
eyelets E1~ E2. Yane S is alao pro~ideà wlth beari~
eyeleta E3, E4. Brackets B1, B2 attached to b~se plate 1 ha~re fuLrther eyelcts E5, E6. A bcarin~; rod N i s threaded th.roush all ~lx eyelets and i~ may be commo~l to seYeral display clement~s in a ro~. Yane ~i includes an angle brac~cet por l:ion ~ tha* rctains b~r L in position on ~ane S but allo~s i* $o rotate ~lishtly rel~ti.ve to the ~ran~, about: th~ same axi~ as the ~ra;le it~elf rotates.
T~p portion T of bar L can come into contact ~i.th holdin~ po(~ H and i~ arranged to be flared out so tllat it presents to polc ~1 a co~tact surface of lar~e arcaO This r~s~ tS in ~; StI`On~!~; attracti;~n between ~h(3 tw~ wh~3n p~le 35 H ~.s masncti~ed, eYen if thore are pArtiOle~ of ~ri~
- ~rnpped ~otween tip T nnd pole ri.

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Claims (18)

WHAT IS CLAIMED IS:

1. A display device including display elements arranged in a number of groups, each display element within one of said groups forming a set together with corresponding display elements of the other groups, each said display element including a member movable between first and second positions in which said display element has different appearances, a permanent magnet coupled to said movable member, a part of ferromagnetic material associated with said movable member, first electromagnet means arranged when energised to act upon said permanent magnet to urge said member to move from one to the other of said positions, second electromagnet means operable when energised to exert force upon said part, said part being arranged in response to pre-determined excitation of said second electromagnet means to inhibit motion of said movable member when said member is in one of said positions, means connecting said first electromagnet means in a said group so that they can be energised together and means connecting said second electromagnet means in a said set so that they can be energised together whereby display elements may be selectively set.

2. A display device as claimed in claim 1, wherein said permanent magnet is attached to said movable member.

3. A display device as claimed in claim 2, wherein said part is loosely attached for limited relative movement to said movable member.

4. A display device as claimed in claim 1, wherein said part is pivoted.

5. A display device as claimed in claim 4, wherein said movable member is pivoted, and said part is pivoted along the same axis.

6. A display device as claimed in claim 1, wherein a said part and said second electromagnet means are arranged to inhibit movement of a said movable member in only one of said positions.

7. A display device as claimed in claim 1, wherein a said part and said second electromagnet means are arranged to inhibit movement of a said movable member in both of said positions.

8. A display device as claimed in claim 1, wherein each of said first and second electromagnet means includes a core of ferromagnetic material of low remanence.

9. A display device as claimed in claim 1, wherein each said display element appears in one of its positions as a substantially rectangular area, said second electro-magnet means including a pole tip disposed adjacent a corner of said rectangular area.

10. A display device as claimed in claim 1, wherein said first electromagnet means in a said group are connected in series and said second electromagnet means in a said set are connected in series.
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11. A display device as claimed in claim 1, wherein selected display elements within a said group are switched from said first to said second positions and at the same time all the display elements of a different said group are switched from said second to said first positions.

12. A display device including a plurality of display elements, each display element including a member movable between first and second positions in which said display element presents contrasting appearances, first electromagnet means having a core of ferromagnetic material and being arranged to urge said member to move from one to the other of said positions and second electromagnet means having a core of ferromagnetic material and being arranged to inhibit movement of said member between said positions urge by said first electromagnet means, whereby said display elements may be selectively set by activating their corresponding first electromagnet means and simultaneously activating particular ones or their corresponding second electromagnet means so as to allow movement of only selected members.

13. A display device as claimed in claim 12, wherein said display elements are arranged in a plurality of groups, each display element of one of said groups forming a set together with corresponding display elements of the other groups, all said first electromagnet means in a said group being activated simultaneously together with all of said second electromagnet means in selected said sets.

14. A display device as claimed in claim 12, wherein said first electromagnet means acts on a permanent magnet attached to said movable member.

15. A display device as claimed in claim 12, wherein said second electromagnet means acts on a part of low-remanence magnet material arranged for movement with said movable member.

16. A display device as claimed in claim 12, wherein said second electromagnet means are arranged in inhibit movement of a said movable member in only one of said positions.

17. A display device as claimed in claim 12, wherein said second electromagnet means are arranged to inhibit movement or a said movable member in both of said positions.

18. A display device as claimed in claim 13, wherein said first electromagnet means in a said group are connected in series and said second electromagnet means in a said set are connected in series.