CA1063570A - Light reflector structure - Google Patents
Light reflector structureInfo
- Publication number
- CA1063570A CA1063570A CA008,999A CA8999A CA1063570A CA 1063570 A CA1063570 A CA 1063570A CA 8999 A CA8999 A CA 8999A CA 1063570 A CA1063570 A CA 1063570A
- Authority
- CA
- Canada
- Prior art keywords
- reflector
- front face
- reflecting
- cells
- reflector structure
- 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.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/12—Reflex reflectors
- G02B5/122—Reflex reflectors cube corner, trihedral or triple reflector type
- G02B5/124—Reflex reflectors cube corner, trihedral or triple reflector type plural reflecting elements forming part of a unitary plate or sheet
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
- E01F9/00—Arrangement of road signs or traffic signals; Arrangements for enforcing caution
- E01F9/50—Road surface markings; Kerbs or road edgings, specially adapted for alerting road users
- E01F9/553—Low discrete bodies, e.g. marking blocks, studs or flexible vehicle-striking members
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/12—Reflex reflectors
Abstract
ABSTRACT OF THE DISCLOSURE
A reflector structure for reflecting light falling on the structure back toward the light source, the reflector struc-ture comprising a one-piece substantially rigid body of trans-parent material having a substantially smooth light receiving front face, the body having therein recesses extending from the rear of the body toward the front face of the body and each recess defining a cell surrounded by a support wall, the rear faces of the support walls defining a continuous support surface extending substantially throughout the rear of the body; a reflector sur-face carried by the body in the area corresponding to the support surface, the reflector surface relecting from the reflector struc-ture light falling upon the front face in the area of the front face corresponding to the support surface, the reflector surface serving to reflect light therefrom to render the reflector struc-ture highly visible in daylight.
There is also in combination with the foregoing a plurality of retrodirective reflector elements on the body in the recesses, and oriented in the body to reflect light falling upon the front face, the reflector elements reflecting from the reflector structure light falling upon the front face in the area of the front face corresponding to the cells for reflecting the light back toward the source of light to render said reflector structure highly visible at night.
A reflector structure for reflecting light falling on the structure back toward the light source, the reflector struc-ture comprising a one-piece substantially rigid body of trans-parent material having a substantially smooth light receiving front face, the body having therein recesses extending from the rear of the body toward the front face of the body and each recess defining a cell surrounded by a support wall, the rear faces of the support walls defining a continuous support surface extending substantially throughout the rear of the body; a reflector sur-face carried by the body in the area corresponding to the support surface, the reflector surface relecting from the reflector struc-ture light falling upon the front face in the area of the front face corresponding to the support surface, the reflector surface serving to reflect light therefrom to render the reflector struc-ture highly visible in daylight.
There is also in combination with the foregoing a plurality of retrodirective reflector elements on the body in the recesses, and oriented in the body to reflect light falling upon the front face, the reflector elements reflecting from the reflector structure light falling upon the front face in the area of the front face corresponding to the cells for reflecting the light back toward the source of light to render said reflector structure highly visible at night.
Description
The present invention is directed to an improved reflector structure that is highly visible both in daylight and at night, The present invention provides a reflector atructure for reflecting light back toward the source thereof, said reflector structure comprising a one-piece substantially rigid body of - :
transparent material having a substantially smooth light receiv-ing front face, said body having therein a plurality of recesses extending from the rear thereof toward said front face and each defining a cell surrounded by a support wall, the rear faces of said support walls defining a continuous support surface extending -substantially throughout the rear of said body, and a plurality of retrodirective reflector elements o~ said body in said recesses and oriented therein to reflect light falling upon said front face, said reflector elements reflecting from said reflector structure light falling upon said front face in the area thereof correspond-ing to said cells for reflecting the light back toward the source thereof to render said reflector structure highly visible at night.
Further features and advantages of the invention together with its organization and method of operation, will best be understood by -.
reference to the following specification taken in connection with the accompanying drawings, in which:
Figure 1 is a d$agrammatic view illustrating the placement of pavement markers along a highway the pavement markers incorporating therein reflector structures of the present invention;
Figure 2 is a perspective view of a pavement marker carrying thereon a reflector structure of the present invention;
, .. ~ Figure 3 is a view of the rear of the pavement marker of Figure , ~
transparent material having a substantially smooth light receiv-ing front face, said body having therein a plurality of recesses extending from the rear thereof toward said front face and each defining a cell surrounded by a support wall, the rear faces of said support walls defining a continuous support surface extending -substantially throughout the rear of said body, and a plurality of retrodirective reflector elements o~ said body in said recesses and oriented therein to reflect light falling upon said front face, said reflector elements reflecting from said reflector structure light falling upon said front face in the area thereof correspond-ing to said cells for reflecting the light back toward the source thereof to render said reflector structure highly visible at night.
Further features and advantages of the invention together with its organization and method of operation, will best be understood by -.
reference to the following specification taken in connection with the accompanying drawings, in which:
Figure 1 is a d$agrammatic view illustrating the placement of pavement markers along a highway the pavement markers incorporating therein reflector structures of the present invention;
Figure 2 is a perspective view of a pavement marker carrying thereon a reflector structure of the present invention;
, .. ~ Figure 3 is a view of the rear of the pavement marker of Figure , ~
2;
Figure 4 is an enlarged plan view of a reflector structure made '' 11;2 .' . . . .
- : .:
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in accordance with the present invention;
Figure ~ is a fragmentary enlarged plan view of the rear of the l~wer righthand corner of the reflector structure of Figure 4, the backing member having been broken away;
Figure 6 is a view in section along the line 6-60~f .'~. ..
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... . . . . .. . I . .. ~ . . ~ . ..
: ~ , . ,; .; . , ~ . . . . .
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Figure 5.
Figure 6A is a vlew similar to Flgure 6 and showing a modlfication Or the rerlector structure;
Figure 6B is another view similar to Figure 6 and il-5 lustrating another modiricatlon o~ the rerlector structure; :
Figure 7 is a view ln vertlcal sectlon on a still~urther enlarged scale along the line 7-7 of Flgure 4;
Figure 8 is a rurther enlarged view o~ the righthand end o~ the rerlector structure Or Figure 4 as viewed in the dlrection of the arrows along the l~ne 8-8 o~ Figure 7;
Figure 9 is a view Or a stop slgn havlng the letters thereon rormed from retrorerlectlve sheets made ln accordance with the present invention;
Figure 10 is a ~ragmentary plan view on an enlarged scale of that portion o~ Flgure 9 enclosed wlthin the clrcle marked 10;
Figure 11 is a ~urther enlarged plan vlew o~ that portion Or Figure 10 enclosed wlthln the dotted area marked 11; and Flgure 12 ls a vlew in vertical section along the . line 12-12 o~ Figure 11.
~: Referring to Figures l to 3 of the drawings, there :. ~
is illustrated a highway marker 100 which incorporates therein two reflector structures 200 made in accordance with and em-bodylng the princlples of the present lnvention. The highway marker 100 is particularly userul in indlcating lanes ln a highway, such ror example as lllustrated ln Figure 1, whereln a hlghway 50 is divlded lnto four lanes 51, 52, 53 and 54.
In order to mark the boundaries o~ the lanes 51, 52, 53 and 54, a plurality Or the highway markers 100 are arranged in aligned rows thus to direct lanes Or trarfic respectively : -3-- .
along the highway lanes 51, 52J 53 and 54 of the hlghway 50.
It wlll be appreclated that ln the use of the high-way markers 100, it is hlghly desirable bhat the markers 100 be fully visible both ln the dayllght and at night; the day-time visibllity is provlded by random light falling on the re-flector structure 200 and being specularly reflected thereby into the eyes of the drivers, and the nlghttime vislbillty ls provided by the llght ~rom the headlights of automobiles fall--; ing upon the reflector structures 200 and being retrodlrective-ly re~lected thereby lnto the eyes of the drlvers. In order to mount and hold the reflector structures 200 in the prefer-red operatlng posltlon upon the hlghway 50, for example, the ~ hlghway markers 100 lnclude a metal base 101 having upstanding - side walls 102 ~oined by a plate 103 that ls adapted to be dlsposed upon the surface of the associated highway, the slde walls 102 including portions 104 dlsposed below the plate 103 and extendlng into grooves in the hlghway, a suitable resln -such as an epoxy resln being provlded ~irmly to mount and se-cure the base 101 in positlon on the highway. A palr of mount-.
ing plates 105 also extend between the side walls 102 and are lnclinqd at an angle o~ ~or example 30 with respect to the plate 103 to mount the two rerlector structures 200 in the in-clined positions shown.
."
- The details of constructlon of the reflector struc-tures 200 are illustrated ln Flgures 4 to 8 of the drawingsJ
wherein it will be seen in Figure 4 that each reflector struc-ture 200 lncludes a body 201 of synthetic organic plastic resin, the preferred resin being a methyl methacrylate resin, the body 201 providing a substantially flat front race 202 and a substantlally flat rear face 203. In outline as vlewed in Figure 4, the reflector structure 200 is in the general form ., .
.; .
~ ,. . .
of a trapezold having a longer edge 205 normally arlented up-wardly in use, a shorter lower edge 206 and a palr of normally upwardly and outwardly incllned slde edges 207 and 208.
A plurallty of recesses or cells 210 are provlded ln the rear ~ace 203 o~ the body 201, the recesses also servlng to define support walls or ribs 211 that surround each of the recesses 210, the cells 210 being rectangular as viewed per-.
pendicular to the front face 202 as in Flgure 4 but belng es-~entially square when viewed ln the directlon of the arrows .': 10 along the llne 8-8 ln Figure 7 (see the lllustratlon ln Flgure ` 8) and in effect constltuting,lslands in the rear,.face 203. In . order to serve at nlght as a reflector for llght from the head-,' llghts o~ an approachlng automoblle, each of the cells 210 ls provlded`throughout the area thereof wlth a plurallty of re-. 15 ~lector elements 220, the reflector elements 220 being of the ,~ retrodlrectlve type and speclflcally of the cube corner type. , ~; Referrlng partlcularly to Flgure 8, lt wlll be seen that each , : !
' o~ the cells 210 lncludes four reflector elements 220, each of , :~
the reflector elements 220 belng square ln plan vlew as seen ' :
, ~i, 20 ln Flgure 8 with four of the reflector elements 220 arranged ' 7 '' to form a larger square completely fllllng the assoclated cell ,- -~
210. Each reflector element 220 further lncludes three re-flectlng surfaces 221, 222 and 223 dlsposed mutually perpen-. dlcular one to the other and ~olnlng a rear corner or apex 224 .~',, 25 and along edges 225, 226 and 227 extendlng forwardly from the ;~: corner 224; more particularly, the edge 225 ls dlsposed be-.. ~ tween the reflectlng surfaces 221 and 222, the edge 226 1B
:~ disposed betwen the reflectlng surfaces 222 and 223, and the , .
',:' edge 227 is disposed between the reflectlng sur~aces 221 and 223. It further ls polnted out that the edges 225 and 226 are , dlrected toward and termlnate 3t polnts lntermedllte the ends ' .
.' .
:1063570 of the ad~acent slde of the reflector element 220, whereas the edge 227 extends to and termlnates at a corner of the reflec-tor element 220. It will be appreciated that each of the re-flector elements 220 comprlses a triple mirror reflex reflec-tor that serves effectively to reflect retrodlrectively ln-cident light falling thereon.
Each of the reflector elements 220 also has a cube - corner axis about which the reflecting surfaces 221, 222 and 223 are symmetrically arranged, and in order to obtain good reflectlon, it is deslrable that the light from headlights entering the reflector element 220 be directed along llnes es--.
sentially parallel to the cube corner axls 228. In order to accomplish thls, the cube corner axes 228 have been arranged at an acute angle with respect to the front face 202, and specifically at an angle of approximately 65 30' with respect thereto, and ln use are dlsposed at an angle of approximately ; 24 30' with respect to the horizontal. Thls inclination o~ ;
the cube corner axes has been found desirable in order to per-mit the front surface 202 to be inclined at an angle of approx-20 imately 30 wlth respect to the horizontal ln use and stlll ;~
; obtain a good reflected signal from the reflector elements 220 - when light falls thereon from the headlights of oncoming ve-. . .
hicles. More particularly, lt has been found that ln use the front face 202 o~ the reflector body 201 is wiped clean and not too greatly abraded by automobile tlres passing thereover provided that the front face 202 is disposed at an angle of approximately 30 with respect to the horizontal, l.e., the .
position illustrated in Figure 7 of the drawings. Moreover, the light emanating from oncoming automobiles is practically parallel to the highway surface at distances from which the marker 100 must be viewed, whereby the light from the head-,~ :
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~ . . , ~ .. .. .. . . . .
lights of oncoming vehicles strikes the front face 202 at an acute angle of approximately 30, The manner ln which the reflector elements 220 oper-ate to re~lect incldent light ~alling upon the ~ront face 202 at an acute angle of about 30 back toward the source of the incident llght as lllustrated in Figure 7. An incident ray 240 from the headlights of an oncoming vehicle directed gener-ally horizontally strikes the front surface 202 at an angle of about 30 and in passlng into the body 201 is refracted 3S at 240a into a path substantially parallel to the cube corner axis 228 of the associated reflector element 220. The ray 240a strikes at least two o~ the re~lecting sur~aces 221, 222 and 223 of the reflector element 220 and ls reflected back therefrom as at 240b through the body 201 and to the front face 202. At the front ~ace 202, the ray 240b ls re~racted to provide the exit ray 240c which is directed rearwardly toward the source of the incident ray 240 and substantially parallel to the incident ray 240.
From Flgures 4, 5 and 8 it will be seen that sub-20 stantially 50% Or the total area of the rear o~ the reflector body 201 ls devoted to the ~lat sur~ace 203 and substantially 50% of the total area of the rear o~ the body 201 is devoted ? to the cells 210 havlng disposed therein the reflector elements 220~ It also is pointed out that the rear sur~ace 203 is con-25 tinuous in the sense that any point on the surface can be reached from any other point on the surface without leaving the sur~ace, and it also is pointed out that each o~ the cells 210 is completely surrounded by the walls 211 and the area thereof completely surrounded by the sur~ace 203. Withln each 30 of the cells 210, the area thereof is completely filled by closely packed and interfltting regular geometric shapes~ the reflector elements 220 havlng square outlines as vlewed in Figure 8 and rectangular outlines as viewed in Figures4 and 5, all as has been explained hereinabove. There more specifical-- ly is provided in each cell 210 four Or the rerlector elements - 5 220J the reflector elements 220 having a rirst orientation ; with respect to the body 201 in the vertlcal row of cells 210 .: , , .
dlsposed to the left in Figure 8, and having a second and dlf~
rerent orientation with respect to the body 201 in the vertical ~- row disposed to the right ln Figure 8. It wlll be understood that other types of retrodirective reflector elements may be used in place Or the reflector elements 220J and other geo-metric ahapes and other arrangements of the reflector surfaces ~ can be utillzed effectively in the present invention.
- It has been found that adequate daytime visibility and nighttime vlslbillty is provided by the reflector struc-... , ~, . .
ture 100 when the area of the surface 203 includes rrom about 10~ to about 90% of the total area of the rear of the body 201 and conversely, when the comblned area of the cells 210 in-cludes rrom about 10~ to about 90~ of the total area of the . 20 rear of the body 201J the preferred construction being one in whlch approximately 50% of the t~tal area of the rear of the body 201 is devoted to the surface 203 and approximately 50~
of the rear of the body 201 i8 devoted to the cells 210. In -thls connection it i8 noted that in daylight the cells 210 ap-~ 25 pear dark and contribute substantially no signal and convers,e-- ly at night the surface 203 appears dark and contributes sub-~: .
stantially no slgnal. It further is desirable that the re-flector structure 200 when vlewed from the front at a dlstance from about one hundred feet or more appear unlformly llghted throughout ~he area thereof and appear to be of the same shape both when llghted by dayllght ralling upon the rront face in . . . - . . - .
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the area thereof corresponding to the surface 203 ~or the re-flecting of daylight therefrom and when lighted by llght ~rom an oncomlng vehicle falling upon the front ~ace 202 in the area thereo~ corresponding to the cells 210 ~or reflectlng light back toward the vehicle. To thls end the ma~or dimen-sions of each of the cells 210 as viewed ln the front face 202 is no greater than about 0.35 lnch and the dlstances between ad~acent ones of the cells 210 as viewed in the front face 202 is no greater than about 0.35 inch. When the parts have these . :
:~ 10 dimensions, the human eye at one hundred ~eet cannot distin-: guish between or resolve the indivldual elements seen through .. ~. . .
the ~ront ~ace 402, whereby the front ~ace 202 appears to be unl~ormly llghted and o~ uni~orm shape both in the daylight when lighted by random light and at night when lighted by the ;
. 15 headlights of an oncomlng vehicle.
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The rear of the reflector structure 200 is sealed by a backlng member 250 which ln the rorm o~ the inventlon lllus-; trated ln Flgures 6 and 7 is in the rorm of a thln metal roil secured to the surface 203 throughout the area thereof by a ~ . .
thin film-like coating 255 o~ heat-sealable synthetlc plastlc materlal that is ~usion bonded upon both the surface 203 and . the adlacent sur~ace of the metal ~oil 250. The metal foll ; 250 may be formed ~or example o~ lead or alumlnum metal, and may have a thlckness ln the range from about 1 mll to about 5 mlls.
The backing member 250 serves to cover and hermetic-ally to seal each o~ the cells 210 in a manner independent o~
: each and every other cell 210 in the reflector structure 200.
. 30 As a result, the backing member 250 serves positively to ex- .
clude water, dirt and the like from the cells 210 and thus to _g_ .:
' . .
prevent the placement of such materlals upon the reflecting surraces 221, 222 and 223 of the reflector elements 220, there-- by to preserve unimpaired the optimum light re~leçting proper-tles thereof. Slnce each of the cells 210 is lndlvldually 5 sealed lndependent of each and every other cell, any break in the backing member 250 or ln the plastic body 201 which may permit access of water, dirt and the llke to one cell wlll not adversely afrect other cells 210 whlch are independently her-metlcally sealed. Consequently, the reflector structure 210 10 exhibits greater weatherablllty and durabllity in use, even when the reflector structure is e*tremèly thln, as wlll be ex-plained more fully herelnafter3 slnce a break or impairment in one of the cells 210 will not be propagated to ad~acent cells 210 in accordance with the present invention.
It further is polnted out that the support walls 211 -~
extend throughout the rear area of the plastic body 201 and in the flnal assembly of the re~lector structure 200 on the marker base 101 distribute the forces applled to the front face 202 throughout the area of the plastlc body 201. In other words, 20 there ls support for the plastlc body 201 throughout the area thereof`, the only portlons not having direct support belng ,in the lndlvldual cells 210. As a consequence, the completed re-rlector structure 200 has great strength even when the total thickness thereof is only a rractlon of an inch, all as will 25 be expla ined more fully hereinafter.
The coating 255 is transparent, whereby the surface of the backing member 250 disposed toward the rear face 203 of ~ the reflector body 201 is visible, and prererably forms the - reflecting surface for reflecting daylight to achieve dayllght . . .
30 visibillty of the reflector structure 200. Alternatively, a light reflecting ~ilm such as a metalized ~ilm, may be placed , on the sur~ace 203 or on the front surface 202 that corresponds to and ls coextensive with the surface 203. However, it will be appreciated that it is prererrèd to protect the re~lectlng SUrface givlng daylight vlslblllty, wherefore the utlllzatlon of the front surface of the backlng member 250, whlch may be - formed o~ pollshed alumlnum, for example, as the dayllght re-flectlng sur~ace ls to be preferred.
;~ It also ls pointed out that the re~lector body 201 may be formed of clear synthetic organlc plastic resln, where-by a whlte beam of llght 18 reflected thereby both ln dayllght and at nlght. However, a color such as red, yellow, blue and the like may be incorporated ln the body 201, thereby to glve a colored signal both ln dayllght and at nlght. Alternatlvely, the reflectlng surfaces of the body 201 may be colored, there-by to glve colored reflectlons therefrom.
The reflector structure 200 ls conveniently mountedupon the highway-marker base 101 by means o~ a suitable resln, an epoxy resln belng preferred for thls purpose. In a typlcal constructlon of the hlghway marker 100 and Or the reflector structure 200 used thereln, the edge 205 has a length of 4.0 lnches; the edge 206 has a length of 3.675 lnches; the edges 207 and 208 have a length of o.85 lnch; the dlstance between the surfaces 202 and 203 ls 0.105 lnch; the dlstance between , ..................................................................... . ..
the corner 224 and the ad~acçnt surrace of the backlng member 250 ls 0.010 lnch; the length of the slde of each of the cells 210 as vlewed ln Flgure 8 ls 0.08 lnch; the vertlcal dimenslon of each cell 210 as vlewed in Flgure 4 1~ 0.10 lnch; and the ~, wl~th of each slde wall 211 between ad~acent cells 210 ls 0.04 lnch9 the wldth thereo~ preferably belng at least about 0.01 lnchO
In a first modlflcatlon of the reflector structure ; -11 -'-`' ~ :
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200, the coating 255 may be simply an adheslve that sets at room temperature rather than a heat-sealable adhesive of the type descrlbed hereinabove In another modlficatlon of the invention, it is contemplated that the adheslve coating 255 be light re~lecting rather than light transmitting whereby the adhesive coating 255 constitutes a reflecting surface through-out the area of the rear surface 203, thereby to provide for - the reflection of daylight for daytime visibility. In other modifications, the desired dayllght reflecting areas are paint-ed to provide the desired color and daylight reflecting charac-teristics.
There is shown in Flgure 6A of the drawings a stlll further modl~ication Or the present invention wherein the backing member 250A is a sheet of synthetic organic plastic resin, such as a sheet of acrylic film that is ~olned directly to the reflector body 201 as by ultrasonic welding. In this form of the invention, inasmuch as the film 250A is transpar-ent, selected portions thereof corresponding to the rear sur- -face 203 are rendered reflective as by metalizing at 251A to 20 render that area light re~lecting to provide daylight visibil- -ity. It will be understood that the sheet 250A serves hermet-ically to seal the cells 210, thereby to provide all of the ad-vantages of the backing member 250 described above wlth respect to Figure 6. In yet another form of the lnvention, the film 250A may be opaque and light diffusing, ln which case there is no need to provide the metallized layer 251A illustrated in Figure 6A.
Referrlng to Figure 6B of the drawings, there is shown a further modification of the invention wherein the several reflecting sur~aces 221, 222 and 223 on each reflector . - .
element 220 is coated with a thin layer of metal, such as , . ..
~: 1063570 .
aluminum, l.e.~ these surfaces are metalized/ to increase the reflectlvlty thereof at wide entrance angles. More speciflc-ally, each of the rerlecting surfaces 221, 222 and 223 ls pro-vided respectively wlth a thln layer 251B of metal, such as - 5 aluminum,-thereon. In applylng the layers 251B, the entire rear surface of the body 201 may be metalllzed, and thereafter selected areas thereof, such as the surface 203, may have the metal removed therefrom as by a release hot-stamp process.
Referrlng to Figures 9 to 12 of the drawlngs, and speciflcally to Flgure 9, there ls lllustrated therein a stop sign 300 including the usual octagonal shaped support mounted on a post 302. In accordance with the present invention, the letters spelllng out the word "STOP" are formed from a retro-reflective sheet 400. Originally the retroreflective sheet 400 may have been rectangular in shape, for example, and has been cut into the shapes illustrated to provide the various letters on the stop sign 300 by cutting with a scissors, for example.
The details of construction of the retroreflectlve sheet 400 are illustrated in Figures 10 to 12 of the drawlngs, whereln it wlll be seen in Flgure 12 that the sheet 400 ln-cludes a body 401 of synthetlc organic plastlc resin, the pre-ferred resln being a methyl methacrylate resln, the body 401 . .
provldlng a substantlally flat front face 402 and a substan-tially flat rear face 403. A plurality o~ recesses or cells 410 are provlded in the rear face 403 of the body 401, the re-cesses also servlng to define support walls or ribs 411 that surround each of the recesses or ceIls 410, the cells 410 be~
ing square in shape as viewed perpendicular to the rront face 402 and as illustrated in Flgure 11. In order to serve at night as a reflector ~or light ~rom the headllghts of an ap-proaching automobile, each of the cells 410 is provlded through-out the area thereof with a pl~ra~.ity of re~lector elements . 420, the re~lector elements 420 being of the retrodlrectlve type and specifically of the cube corner type havlng the same constructlon as the reflector elements 220 de.scribed above.
However, in the form of the invention illustrated in.~igures 9 to 12, the axes of the reflector elements 420 are disposed normal to the front face 402; the rear apeces of the reflector elements 420 are spaced a small distance forwardly with re-spect to the rear face 403. Summarizing, it will be appreci-ated that each of the reflector elements 420 comprlses a triple .~ mirror reflex reflector that serves effectively to reflect . retrodlrectively lncldent light falllng thereon. :
. Prom Flgures 10 and 11 it wlll be seen that substan- tlally 50~ of the total area of the rear of the reflector body 401 is devoted to the flat rear surface 403 and substantlally 50% of the total area of the rear of the body 401 ls devoted - to the cells 410 havlng dlsposed therein the re~lector ele- .ments 420. It also ls polnted out that the rear surface 403 ..
. 20 ls contlnuous ln the sense that any polnt on the surface can be reached from any other poin~ on the surface without leavlng bhe surface, and it also ls polnted out that each of the cells .
. -410 ls completely surrounded by the walls 411 and the area ` thereof completely surrounded by the surface 403. Wlthln each I ~-Or the cells 41~, the area thereof ls completely fllled by closely packed and lnterfltting regular geometric shapes, the reflector elements 420 havlng square outlines. There more speclfically ls provided in each cell 410 four of the reflector elements 420, the reflector elements having a flrst orienta-tion with respect to the body 401 ln one vertlcal row of cells ~ 410 and havlng a second and different orlentation with respect .~ -14-, . . , - . . . . :
. .
. : , ': . ' . ~. . .
- ~ ' to the body 410 ln the other vertical rows. It wlll be understood that other types of retrodirectlve reflector ele-ments may b~ used ln place of the reflector elements 420, ~ -and other geometrlc shapes and other arrangements of the re-5 flector surfaces can be utllized effectively ln the present invention.
It has been round that adequate night time visl-bility is provlded by the retrodirective sheet 400 when the combined area of the cells 410 includes from about 10% to 10 about 90% of the total area of the rear of the body 401, the preferred construction being one in whlch approximately 50% of the total area of the rear of the body 401 is devoted to the surface 403 and approximately 50,~ of the rear of the body 401 is devoted to the cells 410. In this connection 15 lt is noted that in daylight the cells 410 appear dark and accordingly if posltloned on a contrastingly light or color-ed support 301 will provide daylight visibllity also. Al-ternatively, the Surface 403 or an area corresponding to the surface 403 may be colored or provided with material to give 20 at least specular reflectlon of daylight, whereby the retro-reflective sheet 400 would itself provide good vislbllity ln daylight.
It further is desirable that the retroreflective sheet 400 when viewed from the front at a distance from about 25 one hundred feet or more appear unlfo rmly lighted throughout the area thereof and appear to be of the same shape both when lighted by daylight and when lighted by llght at night from an oncoming vehicle falling upon the front face 402 in the area thereof corresponding to the cells 410 for reflecting light 30 back toward the vehicle, To this end the ma~or dimensions of each of the cells 410 as viewed ln the front face 402 is no greater than about 0.35 inch and the distance between ad~acentones of the cells 410 as viewed in the front ~ace 402 is no greater than about 0.35 lnch~ When the parts have these dimen-slons, the human eye at one hundred reet cannot dlstlngulsh between or resolve the indlvidual elements seen through the ~ront face 402, whereby the front face 402 appears to be unl-formly llghted and o~ uni~orm shape both ln the daylight when llghted by random llght and at nlght when lighted by headlights of an oncomlng vehlcle.
The rear of the retrore~lective sheet 400 is sealed by a backing member 450 which ls prererably a sheet of syn-thetic organic plastic resin, such as a sheqt of acryllc fllm, that is Joined directly to the body 401 as by ultrasonic weld- ;
ing. The backing member 450 serves to cover and hermetically to seal such of the cells 410 in a manner independent o~ each and every other cell 410 in the retrore~lective sheet 400. As a result, the bac~ing member 450 serves positively to exclude water, dirt and the like ~rom the cells 410 and thus to pre-:,~ ,. .
'`~; vent the placement Or such materials upon the ref~ cting sur- ~
. . .
~aces of the reflector elements 420, thereby to preserve unim-palred the optimum light reflecting properties thereo~. Since each of the cells 410 ls indivldually sealed lndependent of each and every other cell, any break ln a cell 410 such as the cuttlng therethrough in the ~ormation o~ a letter from the sheet 400 will not adversely a~fect other cells 410 adJacent thereto which are independently hermetically sealed! Conse-quently, the reflective properties o~ the sheet 400 are sub-stantially unlmpaired by the cuttlng required to form the let-ters as illustrated in Figures 9 to 12, and the resultant cut letter exhlblts greater weatherabillty and durability in use since any break or lmpalrment ln one of the cells 410 wlll not ' : .
.
be propagated to ad~acent cells 410 ln accordance with thepresent inventlon.
The body 401 may be formed of clear synthetic or-ganic plastic resln, whereby a whlte beam of light is reflect-ed thereby at night. However, a color such as red, blue, yel-low and the like may be incorporated in the body 401, thereby to give a colored signal there~rom~ It also will be appreci-ated that the sur~ace 403 or areas on the sheet 400 correspond-ing to the surface 403 may be colored or provlded wlth light reflecting coatings so as to glve at least specular reflectlon 4.
therefrom ln daylight.
The letters ~ormed of the retroreflectlve sheet 400 may be conveniently mounted on the support 301 by means of a suitable resin. In a typical construction of the sheet 400, the distance between the surfaces 402 and 403 is 0.025 lnch;
the dlstance between the front face 402 and the lnnermost -point of the recesses forming the cells 410 is 0.01 inch; the thickness from rront to rear of the reflector elements 420 is approximately 0.01 inch; the length of the side of each of the cells 410 ls 0.04 lnch; the width of each side wall 411 be-tween ad~acent cells 410 is 0.01 inch; and the thlckness o~
the backing member 450 is 0.003 inch. When the retroreflective sheet 400 has the dimensions noted, it can be readily cut into the shape of various indicia including letters~ numerals, ar-rows, and the llke and even if such indicla have compllcatedshapes, all without adversely af~ecting the appearance of the resultant lndicla and without adversely affectlng the retro-; reflecting properties thereof.
From the above it wlll be seen that there has been provided a reflector structure 200 that is useful both for re-flecting daylight falling generally upon the front face 202 .
' 106357Q :
thereof to render the reflector structure 200 highly vlsible in daylight and for reflecting light falling upon the front face 202 to reflect the light back toward the source thereof from the reflector elements 220 to render the reflector struc-. 5 ture 200 hlghly vlslble at night in the headlights of a vehicle directed toward the reflector structur.e 200. The reflector structure 200 more partlcularly has a plurality of lndividuaI
i ., cells 210 on the rear thereof surrounded by walls 211 havlng a rear surface all lylng ln a common plane to provlde a rear face 203, the lndivldual cells 210 comprlslng from about 10 to about 90% of the total area of the rear face, a preferred .. ~ ~ ... .. .
.~ arrangement being one whereln approximately 50~ of the total area of the rear of the body 201 i5 the cells 210.
: Further there ls provided a backlng member 250 her- ~:
metically seallng each of the cells 210 to prevent an entry of water, dirt and the llke therelnto, the rearmost portion 224 of the reflector elements 220 belng spaced forwardly a short :.
distance away from the ad3acent surface of the backlng member ~: 250. As a consequence of this structure, a break ln one cell : 20 210 will not cause the loss of reflectivity ln ad~acent un- ~
:;~ broken cells 210, whereby an unusually thin reflector structure : .
having hlgh strength ls provlded, the walls 211 provldlng sup-: port for the plastlc body 201 throughout the rear thereof. In . short, better weatherability and greater durablllty is provid-.: 25 ed in the reflector structure 200.
It ls preferred that the ma~or dlmension of each of the cells as viewed ln the front face be no greater than about . 0.35 lnch and that the distances between ad~acent cells as vlewed in the front face 202 be no greater than about 0.35 - 30 lnch, whereby when the reflector structure 200 is ~lewed ln the front face 202 at a dlstance of about one hundred feet or ~'' , ,.
,, ' ' ~: .' ' :. .
.' '' more, lt appears uniformly lighted throughout anc of the same shape both when lighted by dayllght f311ing upon the front face 202 and when lighted by light from the headllghts of an oncomlng vehlcle falllng upon the front face and reflected back toward the source of light by the reflector elements~
thereby to glve good vislbility both in daytlme and ln night-tlmeO
Flnally, there has been provided a retroreflectlve sheet 400 which can be readily cut lnto indicia o~ even com-pllcated shape without materlally adversely affecting the ap-pearance of the resultlng lndlcla and wlthout m.aterlally ad-versely affecting the retroreflecting properties thereof~
'' - . , .
; ~ ~ ' , ' ' ., ~ ' "' '' ' -: -, ". .. ..
. ~ . , . . ~:
- : - , . .
: :: . ~ ~ - ,. .
.
.. . .
,
Figure 4 is an enlarged plan view of a reflector structure made '' 11;2 .' . . . .
- : .:
. .
in accordance with the present invention;
Figure ~ is a fragmentary enlarged plan view of the rear of the l~wer righthand corner of the reflector structure of Figure 4, the backing member having been broken away;
Figure 6 is a view in section along the line 6-60~f .'~. ..
, ., , ., ~, .
.. ~ .
. ~ ~
, ~,' ~ . ~
~ -2-. ,.
: ,,~ '. -' ' : "', '~' :, :' -, .
B
... . . . . .. . I . .. ~ . . ~ . ..
: ~ , . ,; .; . , ~ . . . . .
; . . ` . . `
Figure 5.
Figure 6A is a vlew similar to Flgure 6 and showing a modlfication Or the rerlector structure;
Figure 6B is another view similar to Figure 6 and il-5 lustrating another modiricatlon o~ the rerlector structure; :
Figure 7 is a view ln vertlcal sectlon on a still~urther enlarged scale along the line 7-7 of Flgure 4;
Figure 8 is a rurther enlarged view o~ the righthand end o~ the rerlector structure Or Figure 4 as viewed in the dlrection of the arrows along the l~ne 8-8 o~ Figure 7;
Figure 9 is a view Or a stop slgn havlng the letters thereon rormed from retrorerlectlve sheets made ln accordance with the present invention;
Figure 10 is a ~ragmentary plan view on an enlarged scale of that portion o~ Flgure 9 enclosed wlthin the clrcle marked 10;
Figure 11 is a ~urther enlarged plan vlew o~ that portion Or Figure 10 enclosed wlthln the dotted area marked 11; and Flgure 12 ls a vlew in vertical section along the . line 12-12 o~ Figure 11.
~: Referring to Figures l to 3 of the drawings, there :. ~
is illustrated a highway marker 100 which incorporates therein two reflector structures 200 made in accordance with and em-bodylng the princlples of the present lnvention. The highway marker 100 is particularly userul in indlcating lanes ln a highway, such ror example as lllustrated ln Figure 1, whereln a hlghway 50 is divlded lnto four lanes 51, 52, 53 and 54.
In order to mark the boundaries o~ the lanes 51, 52, 53 and 54, a plurality Or the highway markers 100 are arranged in aligned rows thus to direct lanes Or trarfic respectively : -3-- .
along the highway lanes 51, 52J 53 and 54 of the hlghway 50.
It wlll be appreclated that ln the use of the high-way markers 100, it is hlghly desirable bhat the markers 100 be fully visible both ln the dayllght and at night; the day-time visibllity is provlded by random light falling on the re-flector structure 200 and being specularly reflected thereby into the eyes of the drivers, and the nlghttime vislbillty ls provided by the llght ~rom the headlights of automobiles fall--; ing upon the reflector structures 200 and being retrodlrective-ly re~lected thereby lnto the eyes of the drlvers. In order to mount and hold the reflector structures 200 in the prefer-red operatlng posltlon upon the hlghway 50, for example, the ~ hlghway markers 100 lnclude a metal base 101 having upstanding - side walls 102 ~oined by a plate 103 that ls adapted to be dlsposed upon the surface of the associated highway, the slde walls 102 including portions 104 dlsposed below the plate 103 and extendlng into grooves in the hlghway, a suitable resln -such as an epoxy resln being provlded ~irmly to mount and se-cure the base 101 in positlon on the highway. A palr of mount-.
ing plates 105 also extend between the side walls 102 and are lnclinqd at an angle o~ ~or example 30 with respect to the plate 103 to mount the two rerlector structures 200 in the in-clined positions shown.
."
- The details of constructlon of the reflector struc-tures 200 are illustrated ln Flgures 4 to 8 of the drawingsJ
wherein it will be seen in Figure 4 that each reflector struc-ture 200 lncludes a body 201 of synthetic organic plastic resin, the preferred resin being a methyl methacrylate resin, the body 201 providing a substantially flat front race 202 and a substantlally flat rear face 203. In outline as vlewed in Figure 4, the reflector structure 200 is in the general form ., .
.; .
~ ,. . .
of a trapezold having a longer edge 205 normally arlented up-wardly in use, a shorter lower edge 206 and a palr of normally upwardly and outwardly incllned slde edges 207 and 208.
A plurallty of recesses or cells 210 are provlded ln the rear ~ace 203 o~ the body 201, the recesses also servlng to define support walls or ribs 211 that surround each of the recesses 210, the cells 210 being rectangular as viewed per-.
pendicular to the front face 202 as in Flgure 4 but belng es-~entially square when viewed ln the directlon of the arrows .': 10 along the llne 8-8 ln Figure 7 (see the lllustratlon ln Flgure ` 8) and in effect constltuting,lslands in the rear,.face 203. In . order to serve at nlght as a reflector for llght from the head-,' llghts o~ an approachlng automoblle, each of the cells 210 ls provlded`throughout the area thereof wlth a plurallty of re-. 15 ~lector elements 220, the reflector elements 220 being of the ,~ retrodlrectlve type and speclflcally of the cube corner type. , ~; Referrlng partlcularly to Flgure 8, lt wlll be seen that each , : !
' o~ the cells 210 lncludes four reflector elements 220, each of , :~
the reflector elements 220 belng square ln plan vlew as seen ' :
, ~i, 20 ln Flgure 8 with four of the reflector elements 220 arranged ' 7 '' to form a larger square completely fllllng the assoclated cell ,- -~
210. Each reflector element 220 further lncludes three re-flectlng surfaces 221, 222 and 223 dlsposed mutually perpen-. dlcular one to the other and ~olnlng a rear corner or apex 224 .~',, 25 and along edges 225, 226 and 227 extendlng forwardly from the ;~: corner 224; more particularly, the edge 225 ls dlsposed be-.. ~ tween the reflectlng surfaces 221 and 222, the edge 226 1B
:~ disposed betwen the reflectlng surfaces 222 and 223, and the , .
',:' edge 227 is disposed between the reflectlng sur~aces 221 and 223. It further ls polnted out that the edges 225 and 226 are , dlrected toward and termlnate 3t polnts lntermedllte the ends ' .
.' .
:1063570 of the ad~acent slde of the reflector element 220, whereas the edge 227 extends to and termlnates at a corner of the reflec-tor element 220. It will be appreciated that each of the re-flector elements 220 comprlses a triple mirror reflex reflec-tor that serves effectively to reflect retrodlrectively ln-cident light falling thereon.
Each of the reflector elements 220 also has a cube - corner axis about which the reflecting surfaces 221, 222 and 223 are symmetrically arranged, and in order to obtain good reflectlon, it is deslrable that the light from headlights entering the reflector element 220 be directed along llnes es--.
sentially parallel to the cube corner axls 228. In order to accomplish thls, the cube corner axes 228 have been arranged at an acute angle with respect to the front face 202, and specifically at an angle of approximately 65 30' with respect thereto, and ln use are dlsposed at an angle of approximately ; 24 30' with respect to the horizontal. Thls inclination o~ ;
the cube corner axes has been found desirable in order to per-mit the front surface 202 to be inclined at an angle of approx-20 imately 30 wlth respect to the horizontal ln use and stlll ;~
; obtain a good reflected signal from the reflector elements 220 - when light falls thereon from the headlights of oncoming ve-. . .
hicles. More particularly, lt has been found that ln use the front face 202 o~ the reflector body 201 is wiped clean and not too greatly abraded by automobile tlres passing thereover provided that the front face 202 is disposed at an angle of approximately 30 with respect to the horizontal, l.e., the .
position illustrated in Figure 7 of the drawings. Moreover, the light emanating from oncoming automobiles is practically parallel to the highway surface at distances from which the marker 100 must be viewed, whereby the light from the head-,~ :
-. - . ~
~ . . , ~ .. .. .. . . . .
lights of oncoming vehicles strikes the front face 202 at an acute angle of approximately 30, The manner ln which the reflector elements 220 oper-ate to re~lect incldent light ~alling upon the ~ront face 202 at an acute angle of about 30 back toward the source of the incident llght as lllustrated in Figure 7. An incident ray 240 from the headlights of an oncoming vehicle directed gener-ally horizontally strikes the front surface 202 at an angle of about 30 and in passlng into the body 201 is refracted 3S at 240a into a path substantially parallel to the cube corner axis 228 of the associated reflector element 220. The ray 240a strikes at least two o~ the re~lecting sur~aces 221, 222 and 223 of the reflector element 220 and ls reflected back therefrom as at 240b through the body 201 and to the front face 202. At the front ~ace 202, the ray 240b ls re~racted to provide the exit ray 240c which is directed rearwardly toward the source of the incident ray 240 and substantially parallel to the incident ray 240.
From Flgures 4, 5 and 8 it will be seen that sub-20 stantially 50% Or the total area of the rear o~ the reflector body 201 ls devoted to the ~lat sur~ace 203 and substantially 50% of the total area of the rear o~ the body 201 is devoted ? to the cells 210 havlng disposed therein the reflector elements 220~ It also is pointed out that the rear sur~ace 203 is con-25 tinuous in the sense that any point on the surface can be reached from any other point on the surface without leaving the sur~ace, and it also is pointed out that each o~ the cells 210 is completely surrounded by the walls 211 and the area thereof completely surrounded by the sur~ace 203. Withln each 30 of the cells 210, the area thereof is completely filled by closely packed and interfltting regular geometric shapes~ the reflector elements 220 havlng square outlines as vlewed in Figure 8 and rectangular outlines as viewed in Figures4 and 5, all as has been explained hereinabove. There more specifical-- ly is provided in each cell 210 four Or the rerlector elements - 5 220J the reflector elements 220 having a rirst orientation ; with respect to the body 201 in the vertlcal row of cells 210 .: , , .
dlsposed to the left in Figure 8, and having a second and dlf~
rerent orientation with respect to the body 201 in the vertical ~- row disposed to the right ln Figure 8. It wlll be understood that other types of retrodirective reflector elements may be used in place Or the reflector elements 220J and other geo-metric ahapes and other arrangements of the reflector surfaces ~ can be utillzed effectively in the present invention.
- It has been found that adequate daytime visibility and nighttime vlslbillty is provided by the reflector struc-... , ~, . .
ture 100 when the area of the surface 203 includes rrom about 10~ to about 90% of the total area of the rear of the body 201 and conversely, when the comblned area of the cells 210 in-cludes rrom about 10~ to about 90~ of the total area of the . 20 rear of the body 201J the preferred construction being one in whlch approximately 50% of the t~tal area of the rear of the body 201 is devoted to the surface 203 and approximately 50~
of the rear of the body 201 i8 devoted to the cells 210. In -thls connection it i8 noted that in daylight the cells 210 ap-~ 25 pear dark and contribute substantially no signal and convers,e-- ly at night the surface 203 appears dark and contributes sub-~: .
stantially no slgnal. It further is desirable that the re-flector structure 200 when vlewed from the front at a dlstance from about one hundred feet or more appear unlformly llghted throughout ~he area thereof and appear to be of the same shape both when llghted by dayllght ralling upon the rront face in . . . - . . - .
- ` ~
the area thereof corresponding to the surface 203 ~or the re-flecting of daylight therefrom and when lighted by llght ~rom an oncomlng vehicle falling upon the front ~ace 202 in the area thereo~ corresponding to the cells 210 ~or reflectlng light back toward the vehicle. To thls end the ma~or dimen-sions of each of the cells 210 as viewed ln the front face 202 is no greater than about 0.35 lnch and the dlstances between ad~acent ones of the cells 210 as viewed in the front face 202 is no greater than about 0.35 inch. When the parts have these . :
:~ 10 dimensions, the human eye at one hundred ~eet cannot distin-: guish between or resolve the indivldual elements seen through .. ~. . .
the ~ront ~ace 402, whereby the front ~ace 202 appears to be unl~ormly llghted and o~ uni~orm shape both in the daylight when lighted by random light and at night when lighted by the ;
. 15 headlights of an oncomlng vehicle.
. .
The rear of the reflector structure 200 is sealed by a backlng member 250 which ln the rorm o~ the inventlon lllus-; trated ln Flgures 6 and 7 is in the rorm of a thln metal roil secured to the surface 203 throughout the area thereof by a ~ . .
thin film-like coating 255 o~ heat-sealable synthetlc plastlc materlal that is ~usion bonded upon both the surface 203 and . the adlacent sur~ace of the metal ~oil 250. The metal foll ; 250 may be formed ~or example o~ lead or alumlnum metal, and may have a thlckness ln the range from about 1 mll to about 5 mlls.
The backing member 250 serves to cover and hermetic-ally to seal each o~ the cells 210 in a manner independent o~
: each and every other cell 210 in the reflector structure 200.
. 30 As a result, the backing member 250 serves positively to ex- .
clude water, dirt and the like from the cells 210 and thus to _g_ .:
' . .
prevent the placement of such materlals upon the reflecting surraces 221, 222 and 223 of the reflector elements 220, there-- by to preserve unimpaired the optimum light re~leçting proper-tles thereof. Slnce each of the cells 210 is lndlvldually 5 sealed lndependent of each and every other cell, any break in the backing member 250 or ln the plastic body 201 which may permit access of water, dirt and the llke to one cell wlll not adversely afrect other cells 210 whlch are independently her-metlcally sealed. Consequently, the reflector structure 210 10 exhibits greater weatherablllty and durabllity in use, even when the reflector structure is e*tremèly thln, as wlll be ex-plained more fully herelnafter3 slnce a break or impairment in one of the cells 210 will not be propagated to ad~acent cells 210 in accordance with the present invention.
It further is polnted out that the support walls 211 -~
extend throughout the rear area of the plastic body 201 and in the flnal assembly of the re~lector structure 200 on the marker base 101 distribute the forces applled to the front face 202 throughout the area of the plastlc body 201. In other words, 20 there ls support for the plastlc body 201 throughout the area thereof`, the only portlons not having direct support belng ,in the lndlvldual cells 210. As a consequence, the completed re-rlector structure 200 has great strength even when the total thickness thereof is only a rractlon of an inch, all as will 25 be expla ined more fully hereinafter.
The coating 255 is transparent, whereby the surface of the backing member 250 disposed toward the rear face 203 of ~ the reflector body 201 is visible, and prererably forms the - reflecting surface for reflecting daylight to achieve dayllght . . .
30 visibillty of the reflector structure 200. Alternatively, a light reflecting ~ilm such as a metalized ~ilm, may be placed , on the sur~ace 203 or on the front surface 202 that corresponds to and ls coextensive with the surface 203. However, it will be appreciated that it is prererrèd to protect the re~lectlng SUrface givlng daylight vlslblllty, wherefore the utlllzatlon of the front surface of the backlng member 250, whlch may be - formed o~ pollshed alumlnum, for example, as the dayllght re-flectlng sur~ace ls to be preferred.
;~ It also ls pointed out that the re~lector body 201 may be formed of clear synthetic organlc plastic resln, where-by a whlte beam of llght 18 reflected thereby both ln dayllght and at nlght. However, a color such as red, yellow, blue and the like may be incorporated ln the body 201, thereby to glve a colored signal both ln dayllght and at nlght. Alternatlvely, the reflectlng surfaces of the body 201 may be colored, there-by to glve colored reflectlons therefrom.
The reflector structure 200 ls conveniently mountedupon the highway-marker base 101 by means o~ a suitable resln, an epoxy resln belng preferred for thls purpose. In a typlcal constructlon of the hlghway marker 100 and Or the reflector structure 200 used thereln, the edge 205 has a length of 4.0 lnches; the edge 206 has a length of 3.675 lnches; the edges 207 and 208 have a length of o.85 lnch; the dlstance between the surfaces 202 and 203 ls 0.105 lnch; the dlstance between , ..................................................................... . ..
the corner 224 and the ad~acçnt surrace of the backlng member 250 ls 0.010 lnch; the length of the slde of each of the cells 210 as vlewed ln Flgure 8 ls 0.08 lnch; the vertlcal dimenslon of each cell 210 as vlewed in Flgure 4 1~ 0.10 lnch; and the ~, wl~th of each slde wall 211 between ad~acent cells 210 ls 0.04 lnch9 the wldth thereo~ preferably belng at least about 0.01 lnchO
In a first modlflcatlon of the reflector structure ; -11 -'-`' ~ :
-` :
.
200, the coating 255 may be simply an adheslve that sets at room temperature rather than a heat-sealable adhesive of the type descrlbed hereinabove In another modlficatlon of the invention, it is contemplated that the adheslve coating 255 be light re~lecting rather than light transmitting whereby the adhesive coating 255 constitutes a reflecting surface through-out the area of the rear surface 203, thereby to provide for - the reflection of daylight for daytime visibility. In other modifications, the desired dayllght reflecting areas are paint-ed to provide the desired color and daylight reflecting charac-teristics.
There is shown in Flgure 6A of the drawings a stlll further modl~ication Or the present invention wherein the backing member 250A is a sheet of synthetic organic plastic resin, such as a sheet of acrylic film that is ~olned directly to the reflector body 201 as by ultrasonic welding. In this form of the invention, inasmuch as the film 250A is transpar-ent, selected portions thereof corresponding to the rear sur- -face 203 are rendered reflective as by metalizing at 251A to 20 render that area light re~lecting to provide daylight visibil- -ity. It will be understood that the sheet 250A serves hermet-ically to seal the cells 210, thereby to provide all of the ad-vantages of the backing member 250 described above wlth respect to Figure 6. In yet another form of the lnvention, the film 250A may be opaque and light diffusing, ln which case there is no need to provide the metallized layer 251A illustrated in Figure 6A.
Referrlng to Figure 6B of the drawings, there is shown a further modification of the invention wherein the several reflecting sur~aces 221, 222 and 223 on each reflector . - .
element 220 is coated with a thin layer of metal, such as , . ..
~: 1063570 .
aluminum, l.e.~ these surfaces are metalized/ to increase the reflectlvlty thereof at wide entrance angles. More speciflc-ally, each of the rerlecting surfaces 221, 222 and 223 ls pro-vided respectively wlth a thln layer 251B of metal, such as - 5 aluminum,-thereon. In applylng the layers 251B, the entire rear surface of the body 201 may be metalllzed, and thereafter selected areas thereof, such as the surface 203, may have the metal removed therefrom as by a release hot-stamp process.
Referrlng to Figures 9 to 12 of the drawlngs, and speciflcally to Flgure 9, there ls lllustrated therein a stop sign 300 including the usual octagonal shaped support mounted on a post 302. In accordance with the present invention, the letters spelllng out the word "STOP" are formed from a retro-reflective sheet 400. Originally the retroreflective sheet 400 may have been rectangular in shape, for example, and has been cut into the shapes illustrated to provide the various letters on the stop sign 300 by cutting with a scissors, for example.
The details of construction of the retroreflectlve sheet 400 are illustrated in Figures 10 to 12 of the drawlngs, whereln it wlll be seen in Flgure 12 that the sheet 400 ln-cludes a body 401 of synthetlc organic plastlc resin, the pre-ferred resln being a methyl methacrylate resln, the body 401 . .
provldlng a substantlally flat front face 402 and a substan-tially flat rear face 403. A plurality o~ recesses or cells 410 are provlded in the rear face 403 of the body 401, the re-cesses also servlng to define support walls or ribs 411 that surround each of the recesses or ceIls 410, the cells 410 be~
ing square in shape as viewed perpendicular to the rront face 402 and as illustrated in Flgure 11. In order to serve at night as a reflector ~or light ~rom the headllghts of an ap-proaching automobile, each of the cells 410 is provlded through-out the area thereof with a pl~ra~.ity of re~lector elements . 420, the re~lector elements 420 being of the retrodlrectlve type and specifically of the cube corner type havlng the same constructlon as the reflector elements 220 de.scribed above.
However, in the form of the invention illustrated in.~igures 9 to 12, the axes of the reflector elements 420 are disposed normal to the front face 402; the rear apeces of the reflector elements 420 are spaced a small distance forwardly with re-spect to the rear face 403. Summarizing, it will be appreci-ated that each of the reflector elements 420 comprlses a triple .~ mirror reflex reflector that serves effectively to reflect . retrodlrectively lncldent light falllng thereon. :
. Prom Flgures 10 and 11 it wlll be seen that substan- tlally 50~ of the total area of the rear of the reflector body 401 is devoted to the flat rear surface 403 and substantlally 50% of the total area of the rear of the body 401 ls devoted - to the cells 410 havlng dlsposed therein the re~lector ele- .ments 420. It also ls polnted out that the rear surface 403 ..
. 20 ls contlnuous ln the sense that any polnt on the surface can be reached from any other poin~ on the surface without leavlng bhe surface, and it also ls polnted out that each of the cells .
. -410 ls completely surrounded by the walls 411 and the area ` thereof completely surrounded by the surface 403. Wlthln each I ~-Or the cells 41~, the area thereof ls completely fllled by closely packed and lnterfltting regular geometric shapes, the reflector elements 420 havlng square outlines. There more speclfically ls provided in each cell 410 four of the reflector elements 420, the reflector elements having a flrst orienta-tion with respect to the body 401 ln one vertlcal row of cells ~ 410 and havlng a second and different orlentation with respect .~ -14-, . . , - . . . . :
. .
. : , ': . ' . ~. . .
- ~ ' to the body 410 ln the other vertical rows. It wlll be understood that other types of retrodirectlve reflector ele-ments may b~ used ln place of the reflector elements 420, ~ -and other geometrlc shapes and other arrangements of the re-5 flector surfaces can be utllized effectively ln the present invention.
It has been round that adequate night time visl-bility is provlded by the retrodirective sheet 400 when the combined area of the cells 410 includes from about 10% to 10 about 90% of the total area of the rear of the body 401, the preferred construction being one in whlch approximately 50% of the total area of the rear of the body 401 is devoted to the surface 403 and approximately 50,~ of the rear of the body 401 is devoted to the cells 410. In this connection 15 lt is noted that in daylight the cells 410 appear dark and accordingly if posltloned on a contrastingly light or color-ed support 301 will provide daylight visibllity also. Al-ternatively, the Surface 403 or an area corresponding to the surface 403 may be colored or provided with material to give 20 at least specular reflectlon of daylight, whereby the retro-reflective sheet 400 would itself provide good vislbllity ln daylight.
It further is desirable that the retroreflective sheet 400 when viewed from the front at a distance from about 25 one hundred feet or more appear unlfo rmly lighted throughout the area thereof and appear to be of the same shape both when lighted by daylight and when lighted by llght at night from an oncoming vehicle falling upon the front face 402 in the area thereof corresponding to the cells 410 for reflecting light 30 back toward the vehicle, To this end the ma~or dimensions of each of the cells 410 as viewed ln the front face 402 is no greater than about 0.35 inch and the distance between ad~acentones of the cells 410 as viewed in the front ~ace 402 is no greater than about 0.35 lnch~ When the parts have these dimen-slons, the human eye at one hundred reet cannot dlstlngulsh between or resolve the indlvidual elements seen through the ~ront face 402, whereby the front face 402 appears to be unl-formly llghted and o~ uni~orm shape both ln the daylight when llghted by random llght and at nlght when lighted by headlights of an oncomlng vehlcle.
The rear of the retrore~lective sheet 400 is sealed by a backing member 450 which ls prererably a sheet of syn-thetic organic plastic resin, such as a sheqt of acryllc fllm, that is Joined directly to the body 401 as by ultrasonic weld- ;
ing. The backing member 450 serves to cover and hermetically to seal such of the cells 410 in a manner independent o~ each and every other cell 410 in the retrore~lective sheet 400. As a result, the bac~ing member 450 serves positively to exclude water, dirt and the like ~rom the cells 410 and thus to pre-:,~ ,. .
'`~; vent the placement Or such materials upon the ref~ cting sur- ~
. . .
~aces of the reflector elements 420, thereby to preserve unim-palred the optimum light reflecting properties thereo~. Since each of the cells 410 ls indivldually sealed lndependent of each and every other cell, any break ln a cell 410 such as the cuttlng therethrough in the ~ormation o~ a letter from the sheet 400 will not adversely a~fect other cells 410 adJacent thereto which are independently hermetically sealed! Conse-quently, the reflective properties o~ the sheet 400 are sub-stantially unlmpaired by the cuttlng required to form the let-ters as illustrated in Figures 9 to 12, and the resultant cut letter exhlblts greater weatherabillty and durability in use since any break or lmpalrment ln one of the cells 410 wlll not ' : .
.
be propagated to ad~acent cells 410 ln accordance with thepresent inventlon.
The body 401 may be formed of clear synthetic or-ganic plastic resln, whereby a whlte beam of light is reflect-ed thereby at night. However, a color such as red, blue, yel-low and the like may be incorporated in the body 401, thereby to give a colored signal there~rom~ It also will be appreci-ated that the sur~ace 403 or areas on the sheet 400 correspond-ing to the surface 403 may be colored or provlded wlth light reflecting coatings so as to glve at least specular reflectlon 4.
therefrom ln daylight.
The letters ~ormed of the retroreflectlve sheet 400 may be conveniently mounted on the support 301 by means of a suitable resin. In a typical construction of the sheet 400, the distance between the surfaces 402 and 403 is 0.025 lnch;
the dlstance between the front face 402 and the lnnermost -point of the recesses forming the cells 410 is 0.01 inch; the thickness from rront to rear of the reflector elements 420 is approximately 0.01 inch; the length of the side of each of the cells 410 ls 0.04 lnch; the width of each side wall 411 be-tween ad~acent cells 410 is 0.01 inch; and the thlckness o~
the backing member 450 is 0.003 inch. When the retroreflective sheet 400 has the dimensions noted, it can be readily cut into the shape of various indicia including letters~ numerals, ar-rows, and the llke and even if such indicla have compllcatedshapes, all without adversely af~ecting the appearance of the resultant lndicla and without adversely affectlng the retro-; reflecting properties thereof.
From the above it wlll be seen that there has been provided a reflector structure 200 that is useful both for re-flecting daylight falling generally upon the front face 202 .
' 106357Q :
thereof to render the reflector structure 200 highly vlsible in daylight and for reflecting light falling upon the front face 202 to reflect the light back toward the source thereof from the reflector elements 220 to render the reflector struc-. 5 ture 200 hlghly vlslble at night in the headlights of a vehicle directed toward the reflector structur.e 200. The reflector structure 200 more partlcularly has a plurality of lndividuaI
i ., cells 210 on the rear thereof surrounded by walls 211 havlng a rear surface all lylng ln a common plane to provlde a rear face 203, the lndivldual cells 210 comprlslng from about 10 to about 90% of the total area of the rear face, a preferred .. ~ ~ ... .. .
.~ arrangement being one whereln approximately 50~ of the total area of the rear of the body 201 i5 the cells 210.
: Further there ls provided a backlng member 250 her- ~:
metically seallng each of the cells 210 to prevent an entry of water, dirt and the llke therelnto, the rearmost portion 224 of the reflector elements 220 belng spaced forwardly a short :.
distance away from the ad3acent surface of the backlng member ~: 250. As a consequence of this structure, a break ln one cell : 20 210 will not cause the loss of reflectivity ln ad~acent un- ~
:;~ broken cells 210, whereby an unusually thin reflector structure : .
having hlgh strength ls provlded, the walls 211 provldlng sup-: port for the plastlc body 201 throughout the rear thereof. In . short, better weatherability and greater durablllty is provid-.: 25 ed in the reflector structure 200.
It ls preferred that the ma~or dlmension of each of the cells as viewed ln the front face be no greater than about . 0.35 lnch and that the distances between ad~acent cells as vlewed in the front face 202 be no greater than about 0.35 - 30 lnch, whereby when the reflector structure 200 is ~lewed ln the front face 202 at a dlstance of about one hundred feet or ~'' , ,.
,, ' ' ~: .' ' :. .
.' '' more, lt appears uniformly lighted throughout anc of the same shape both when lighted by dayllght f311ing upon the front face 202 and when lighted by light from the headllghts of an oncomlng vehlcle falllng upon the front face and reflected back toward the source of light by the reflector elements~
thereby to glve good vislbility both in daytlme and ln night-tlmeO
Flnally, there has been provided a retroreflectlve sheet 400 which can be readily cut lnto indicia o~ even com-pllcated shape without materlally adversely affecting the ap-pearance of the resultlng lndlcla and wlthout m.aterlally ad-versely affecting the retroreflecting properties thereof~
'' - . , .
; ~ ~ ' , ' ' ., ~ ' "' '' ' -: -, ". .. ..
. ~ . , . . ~:
- : - , . .
: :: . ~ ~ - ,. .
.
.. . .
,
Claims (14)
1. A reflector structure for reflecting daylight falling thereon and for reflecting light back toward the source thereof, said reflector structure comprising a one-piece sub-stantially rigid body of transparent material having a substan-tially smooth light receiving front face, said body having there-in a plurality of recesses extending from the rear thereof toward said front face and each defining a cell surrounded by a support wall, the rear faces of said support walls defining a continous support surface extending substantially throughout the rear of said body, a reflector surface carried by said body in the area corresponding to said support surface, said reflect-or surface reflecting from said reflector structure daylight falling upon said front face in the area thereof corresponding to said support surface for reflecting the daylight therefrom to render said reflector structure highly visible in daylight, and a plurality of retrodirective reflector elements on said body in said recesses, and oriented therein to reflect light falling upon said front face, said reflector elements reflect-ing from said reflector structure light falling upon said front face in the area thereof corresponding to said cells for re-flecting the light back toward the source thereof to render said reflector structure highly visible at night.
2. The reflector structure set forth in claim 1, wherein said reflector surface is provided by a thin metal film attached to said support surface.
3. A reflector structure for reflecting light back toward the source thereof, said reflector structure comprising a one-piece substantially rigid body of transparent material having a substantially smooth light receiving front face, said body having therein a plurality of recesses extending from the rear thereof toward said front face and each defining a cell surrounded by a support wall, the rear faces of said support walls defining a continuous support surface extending substan-tially throughout the rear of said body, a plurality of retro-directive reflector elements on said body in said recesses and oriented therein to reflect light falling upon said front face, said reflector elements reflecting from said reflector struc-ture light falling upon said front face in the area thereof corresponding to said cells for reflecting the light back toward the source thereof to render said reflector structure highly visible at night, the major dimension of each of said cells as viewed in said front face being no greater than about 0.35 inch and the distances between adjacent ones of said cells as viewed in said front face being no greater than about 0.35 inch, where-by when said reflector structure is viewed in said front face at a distance of about one hundred feet it appears to be of the same shape both when lighted by daylight falling upon said front face in the area thereof corresponding to said support surface and when lighted by light falling upon said front face in the area thereof corresponding to said cells for reflecting the light back toward the source thereof.
4. A reflector structure for reflecting daylight falling generally upon one face thereof to render the reflect-or structure highly visible in daylight and for reflecting therefrom light falling upon the one face thereof to reflect the light back toward the source thereof to render the reflector structure highly visible at night, said reflector structure com-prising a one-piece substantially rigid body of transparent material having a front face and a rear face, said rear face having a continuous support surface extending substantially throughout the area thereof and having a plurality of recesses each defining a cell surrounded by a support wall, a reflector surface carried by said body in the area corresponding to said support surface, said reflector surface reflecting from said reflector structure daylight falling upon said front face in the area thereof corresponding to said support surface for reflect-ing the daylight therefrom to render said reflector structure highly visible in daylight and a plurality of retrodirective reflector elements on said body in said recesses, said reflector elements reflecting from said reflector structure light falling upon said front face in the area thereof corresponding to said cells for reflecting the light back toward the source thereof to render said reflector structure highly visible at night, the major dimension of each of said cells as viewed in said front face being no greater than about 0.35 inch and the distances between adjacent ones of said cells as viewed in said front face being no greater than about 0.35 inch, whereby when said reflector structure is viewed in said front face at a distance of about 100 feet it appears uniformly lighted throughout and of the same shape both when lighted by daylight falling upon said front face in the area thereof corresponding to said support surface for reflecting the daylight therefrom, and when and when lighted by light falling upon said front face in the area thereof corresponding to said cells for reflecting the light back toward the source thereof.
5. A reflector structure for reflecting daylight falling thereon and for reflecting light back toward the source thereof, said reflector structure comprising a one-piece sub-stantially rigid body of transparent material having a substan-tially smooth light receiving front face, said body having therein a plurality of recesses extending from the rear thereof toward said front face and each defining a cell surrounded by a support wall, the rear faces of said support walls defining a continuous support surface extending substantially throughout the rear of said body, a reflector surface carried by said body in the area corresponding to said support surface, said reflect or surface reflecting from said reflector structure daylight falling upon said front face in the area thereof corresponding to said support surface for reflecting the daylight therefrom to render said reflector structure highly visible in daylight, a plurality of retrodirective reflector elements on said body in said recesses, and oriented therein to reflect light falling upon said front face, said reflector elements reflecting from said reflector structure light falling upon said front face in the area thereof corresponding to said cells for reflecting the light back toward the source thereof to render said reflector structure highly visible at night, and a backing member cover-ing substantially all of the rear of said body and hermetical-ly sealed to said support surface along all portions thereof thus hermetically to seal each of said cells.
6. The reflector structure set forth in claim 5, wherein said backing member is a thin metal foil having a thin film-like coating of heat-sealable synthetic material bonded to the support surface to provide a hermetic seal therebetween.
7. The reflector structure set forth in claim 5, wherein said backing member is a thin metal foil adhesively secured to said support surface.
8. The reflector structure set forth in claim 5, wherein said backing member is a sheet of synthetic organic plastic resin welded to said support surface.
9. The reflector structure set forth in claim 5, wherein said backing member also provides said reflector sur-face.
10. The reflector structure set forth in claim 5, wherein an adhesive layer is provided to secure said backing member to said support surface, said adhesive layer also provid-ing said reflector surface.
11. The reflector structure for providing improved vandal-resistant reflectors, signs and legends having high ret-roreflectivity and good daytime color appearance, said reflector structure comprising a one-piece body of transparent material having throughout the area within its perimeter a substantially smooth light-receiving front face and having a rear surface com-prising, a) a plurality of cube-corner retrodirective reflector elements each having a set of three mutually perpendicular facets, and b) intervening transparent septa, said septa intersecting to form a grid extending throughout said rear surface to divide said rear surface into a plurality of cells, each cell contain-ing at least three of said cube-corner reflector elements and the combined area within said cells being not less than the com-bined area of said septa, said septa having free edges positioned rearward of the front face at least as far as said cube-corner reflector elements which free edges permit the structure to be affixed to a backing to hermetically seal the individual cells, said cube-corner reflector elements being oriented in said cells to reflect light falling upon them through said front face back toward the source thereof to render said reflector structure highly visible at night and said septa reflecting light falling on the front face in areas corresponding thereto to improve the daytime appearance of the structure, each of the said reflector elements having a square outline.
12. A reflector structure for providing improved vandal-resistant reflectors, signs and legends having high ret-roreflectivity and good daytime color appearance, said reflector structure comprising a one-piece body of transparent material having throughout the area within its perimeter a substantially smooth light-receiving front face and having a rear surface com-prising, a) a plurality of cube-corner retrodirective reflector elements each having a set of three mutually perpendicular facets, and b) intervening transparent septa, said septa intersecting to form a grid extending throughout said rear surface to divide said rear surface into a plurality of cells, each cell contain-ing at least three of said cube-corner reflector elements and the combined area within said cells being not less than the com-bined area of said septa, said septa having free edges positioned rearward of the front face at least as far as said cube-corner reflector elements which free edges permit the structure to be affixed to a backing to hermetically seal the individual cells, said cube-corner reflector elements being oriented in said cells to reflect light falling upon them through said front face back toward the source thereof to render said reflector structure highly visible at night and said septa reflecting light falling on the front face in areas corresponding thereto to improve the daytime appearance of the structure, the said reflector structure also including a backing member covering substantially all of the rear of said body and sealed to said free edges along all portions thereof to seal each of said cells.
13. A reflector structure for reflecting light back toward the source thereof, said reflector structure comprising a one piece body of transparent material having a substantially smooth light receiving front face, said body having therein a plurality of rectangular recesses extending from the rear there-of toward said front face and each defining a rectangular cell surrounded by a support wall, the rear faces of said support walls defining a substantially continuous support surface ex-tending substantially throughout the rear of said body, and a plurality of rectangular retrodirective cube corner reflector elements on said body in said recesses and oriented therein to reflect light falling upon said front face, said reflector elements reflecting from said reflector structure light falling upon said front face in the area thereof corresponding to said cells and reflecting the light back toward the source thereof to render said reflector structure highly visible at night.
14. A reflector structure for providing improved van-dal-resistant reflectors, signs and legends having high retrore-flectivity and good daytime color appearance, said reflector structure comprising a one-piece body of transparent material having throughout the area within its perimeter a substantially smooth light-receiving front face and having a rear surface com-prising a plurality of cube-corner retrodirective reflector elements each having a rectangular outline and each having a set of three mutually perpendicular facets, intervening transparent septa, said septa intersecting to form a grid extending through-out said rear surface to divide said rear surface into a plural-ity of rectangular cells, each cell containing at least three of said cube-corner reflector elements and the combined area within said cells being not less than the combined area of said septa, said septa having free edges positioned rearward of the front face at least as far as said cube-corner reflector elements, a reflector surface carried by said body in the area corresponding to said support surface, said cube-corner reflector elements being oriented in said cells to reflect light falling upon them through said front face back toward the source thereof to render said reflector structure highly visible at night and said septa reflecting light falling on the front face in areas corresponding thereto to improve the daytime appearance of the structure.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62572367A | 1967-03-24 | 1967-03-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1063570A true CA1063570A (en) | 1979-10-02 |
Family
ID=24507289
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA008,999A Expired CA1063570A (en) | 1967-03-24 | 1968-01-02 | Light reflector structure |
Country Status (7)
| Country | Link |
|---|---|
| BE (1) | BE711381A (en) |
| CA (1) | CA1063570A (en) |
| DE (2) | DE1772038A1 (en) |
| ES (1) | ES350597A1 (en) |
| FR (1) | FR1554530A (en) |
| GB (1) | GB1189055A (en) |
| SE (1) | SE329862B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4025159A (en) * | 1976-02-17 | 1977-05-24 | Minnesota Mining And Manufacturing Company | Cellular retroreflective sheeting |
| LU74641A1 (en) * | 1976-03-25 | 1977-10-10 | ||
| DE2747324A1 (en) * | 1977-10-21 | 1979-04-26 | Ferro Corp | Retroreflector with angled light transmitting sheet - with refractive front surface and rear surface with reflecting units |
| DE7809465U1 (en) * | 1978-03-30 | 1978-07-13 | Heinz Simon Gmbh & Co Kg, 8950 Kaufbeuren | LIGHT REFLECTOR MADE OF PLASTIC |
| US4801193A (en) * | 1988-03-04 | 1989-01-31 | Reflexite Corporation | Retroreflective sheet material and method of making same |
| US5204731A (en) * | 1989-12-04 | 1993-04-20 | Sokkisha Co., Ltd. | Method and apparatus for measuring the coordinates of a surveyed point |
| US5229882A (en) * | 1990-05-16 | 1993-07-20 | Reflexite Corporation | Colored retroreflective sheeting and method of making same |
| CA2064484C (en) * | 1991-04-11 | 1998-08-11 | William P. Rowland | Retroreflective sheet |
-
1968
- 1968-01-02 CA CA008,999A patent/CA1063570A/en not_active Expired
- 1968-01-25 SE SE01008/68A patent/SE329862B/xx unknown
- 1968-01-26 GB GB4333/68A patent/GB1189055A/en not_active Expired
- 1968-02-17 ES ES350597A patent/ES350597A1/en not_active Expired
- 1968-02-27 FR FR1554530D patent/FR1554530A/fr not_active Expired
- 1968-02-28 BE BE711381D patent/BE711381A/xx unknown
- 1968-03-22 DE DE19681772038 patent/DE1772038A1/en not_active Withdrawn
- 1968-03-22 DE DE19681797632 patent/DE1797632A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ES350597A1 (en) | 1969-11-16 |
| GB1189055A (en) | 1970-04-22 |
| SE329862B (en) | 1970-10-26 |
| BE711381A (en) | 1968-08-28 |
| DE1797632A1 (en) | 1976-12-30 |
| FR1554530A (en) | 1969-01-17 |
| DE1772038A1 (en) | 1971-01-07 |
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