CA1121192A - Curtain for shrouding welding operations - Google Patents
Curtain for shrouding welding operationsInfo
- Publication number
- CA1121192A CA1121192A CA000336534A CA336534A CA1121192A CA 1121192 A CA1121192 A CA 1121192A CA 000336534 A CA000336534 A CA 000336534A CA 336534 A CA336534 A CA 336534A CA 1121192 A CA1121192 A CA 1121192A
- Authority
- CA
- Canada
- Prior art keywords
- curtain
- light
- dye
- combination according
- sheet
- 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
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F9/00—Methods or devices for treatment of the eyes; Devices for putting-in contact lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
- A61F9/04—Eye-masks ; Devices to be worn on the face, not intended for looking through; Eye-pads for sunbathing
- A61F9/06—Masks, shields or hoods for welders
- A61F9/065—Masks, shields or hoods for welders use of particular optical filters
Landscapes
- Health & Medical Sciences (AREA)
- Ophthalmology & Optometry (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Vascular Medicine (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Optical Filters (AREA)
- Illuminated Signs And Luminous Advertising (AREA)
- Curtains And Furnishings For Windows Or Doors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A curtain for surrounding welding and cutting operations, especially electric arc welding and electric arc cutting operations to protect the eyes of otherwise unprotected observers. The curtain contains dyes for the purpose of absorbing radiation of wavelengths of potential hazard to such eyes. Be-cause no dye can absorb all potentially harmful radiation and still provide some visibility, means is provided to improve the protection by means of reducing the exposure of the retina to undesirable intensities by optically enlarging the small arc spot, and by presenting the eye with general area illumination instead of pinpoint illumination.
A curtain for surrounding welding and cutting operations, especially electric arc welding and electric arc cutting operations to protect the eyes of otherwise unprotected observers. The curtain contains dyes for the purpose of absorbing radiation of wavelengths of potential hazard to such eyes. Be-cause no dye can absorb all potentially harmful radiation and still provide some visibility, means is provided to improve the protection by means of reducing the exposure of the retina to undesirable intensities by optically enlarging the small arc spot, and by presenting the eye with general area illumination instead of pinpoint illumination.
Description
gz This invcntion relates to welcling curtains thro-lgll which an objcct on the othcr side can bc sccn.
hlore particularly, this inventioll relates to a transparent wclding curtain which will enable an otherwise-unprotectel observer to observe a welding scene on tlle other side with the Cureatest clarity consistent with the requisite safety from deleterious effects, even if the eye should fixate on the arc spot for an extended period, and with the "yellow" dyed prior art transparent welding curtain there is substantial transmission of radiation - around 390 nm, and the rising segment of the curve at cut-off is at suffi-ciently low wave lengths that there is considerable "bl~le-effect" light trans-mission. A high proportion of photopically visible light is also passed. ~y "cut-off" is meant a relatively narrow ~Yavelength range across whicil the transmission changes rapidly ~in respect to wavelengtll) from a generally lo~
value - 5 to 10% to a generally high value - 70 or 80~.
The prior art curtain often referred to as "amber" colored passes less hazardous "blue-effect" light, but it also has a lesser transmission of photopically visible light than is desirable.
A prior art curtain often referred to as "green" colored admits an excess "blue-effect" light and has less photopically visible transmissivity than even the "amber" curtain.
The present invention is concernccl witll optimi2ing the trade-o~f botwoen thcse t~o competing rcquirclllcnts. This optlmiza-tion may be achieved by utilizing spectral space discrimination using dyes as clescribed below.
This may be used in combination ~ith some or all of the following features:
I. Spatial frequency discrimination using surface refr~ction as described below;
II. Relative light intensity reduction by diffractive scattering, using surface or bulk index of refraction discontinuities as described belo~; and B.
l~LZiL~92 III. Fluorescent wavelellgtll shiftin(l, using ~luorescent dyes as clescribed below.
Pertinent considerations are as follows:
SPECTRAL SPACE DISCRIhlINATION
The energy emitted by an electric welding arc is given out in the form of radiant energy. Such radiant energy consistes of t]le simultaneous emission of electromagnetic waves whose wavelengths include every wavelength - from less than 200 nanometers (nm) to more than 1,400 nm.
Among all the radiations, those of the ultraviolet ~200 - 400 nm), and the shorter-wavelength part of the visible (~00 to about 500 or 550 nm) are the most effective in producing damage to the eye. That is, the radiations whose wavelength is 500 nm and greater are relatively innocllous in callsing damage even l~hen they are present to as large an extent as tl~e group frolll 200 to 500 nm. Therefore a curtain or filter which stops all racliatioll from an arc operation between 200 and 500 nm while allowing the resiclual radiations from 500 to 1,400 nm to pass, will do away witll the po~entially hazardous 200 - 500 nm radiation, while allowing the longer (500 to 1,~00 nm) more innocuous radiation to pass through it. It is important to maximize the amount of the remaining non-hazardous radiations that pass through the cur-
hlore particularly, this inventioll relates to a transparent wclding curtain which will enable an otherwise-unprotectel observer to observe a welding scene on tlle other side with the Cureatest clarity consistent with the requisite safety from deleterious effects, even if the eye should fixate on the arc spot for an extended period, and with the "yellow" dyed prior art transparent welding curtain there is substantial transmission of radiation - around 390 nm, and the rising segment of the curve at cut-off is at suffi-ciently low wave lengths that there is considerable "bl~le-effect" light trans-mission. A high proportion of photopically visible light is also passed. ~y "cut-off" is meant a relatively narrow ~Yavelength range across whicil the transmission changes rapidly ~in respect to wavelengtll) from a generally lo~
value - 5 to 10% to a generally high value - 70 or 80~.
The prior art curtain often referred to as "amber" colored passes less hazardous "blue-effect" light, but it also has a lesser transmission of photopically visible light than is desirable.
A prior art curtain often referred to as "green" colored admits an excess "blue-effect" light and has less photopically visible transmissivity than even the "amber" curtain.
The present invention is concernccl witll optimi2ing the trade-o~f botwoen thcse t~o competing rcquirclllcnts. This optlmiza-tion may be achieved by utilizing spectral space discrimination using dyes as clescribed below.
This may be used in combination ~ith some or all of the following features:
I. Spatial frequency discrimination using surface refr~ction as described below;
II. Relative light intensity reduction by diffractive scattering, using surface or bulk index of refraction discontinuities as described belo~; and B.
l~LZiL~92 III. Fluorescent wavelellgtll shiftin(l, using ~luorescent dyes as clescribed below.
Pertinent considerations are as follows:
SPECTRAL SPACE DISCRIhlINATION
The energy emitted by an electric welding arc is given out in the form of radiant energy. Such radiant energy consistes of t]le simultaneous emission of electromagnetic waves whose wavelengths include every wavelength - from less than 200 nanometers (nm) to more than 1,400 nm.
Among all the radiations, those of the ultraviolet ~200 - 400 nm), and the shorter-wavelength part of the visible (~00 to about 500 or 550 nm) are the most effective in producing damage to the eye. That is, the radiations whose wavelength is 500 nm and greater are relatively innocllous in callsing damage even l~hen they are present to as large an extent as tl~e group frolll 200 to 500 nm. Therefore a curtain or filter which stops all racliatioll from an arc operation between 200 and 500 nm while allowing the resiclual radiations from 500 to 1,400 nm to pass, will do away witll the po~entially hazardous 200 - 500 nm radiation, while allowing the longer (500 to 1,~00 nm) more innocuous radiation to pass through it. It is important to maximize the amount of the remaining non-hazardous radiations that pass through the cur-
2~ tain, because the ability to see the scene thro~lgh tlle curtain clepencls on -the amount o~ visible ligllt lYhiCh ~enetrates thc curtnin ~mcl re~ches the eye.
rllere are thus ttYo m-~eual ly contracl;ctory re(l-lirQIncn-ts ~`or a curtain which allows safe viewing of an electric welding or cutting arc scene. In order to minimize the potential eye hazard, the curtain should stop all wave-lellgths ~rom 200 to 500 or 550 nm or larger. In order to maximize the ability to see the scene, the curtain should pass the maximum of those radiations whicll give rise to the sensation of sight (~00 to 760 nm).
It has been determined as described later, that if the curtain 119'~
transmission cut-off is bet~cen about 500 nm and about 5S0 nm sufficient visible light (witll wavelengtlls betweell about 500 and about 760 nm) will reach the eye, and little enougll residual hazarcll~ill remain, so that such a curtain could constitute a safe and usable welding curtain for passers-by adjacent workers, and supervisors.
Thus, according to the present invention there is provided a curtain for protecting an observer from damage by light from welding arcs, said curtain being sufficiently transparent to see through it an object of sub-stantial size, said curtain comprising:
an organic plastic matrix material which itself is inherently transparent and l~hich is formed into a sheet with a pair of surfaces and a dimension of thickness betl~een said surfaces; and dye distributed throughout said matri~ material, said dye being proviclecl in concentrations which permit the sheet to transmit at least 70~ of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmission of said sheet ~ith dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm.
SPATIAL ~REQUENCY DISCRIMINATION
Radiations from 200 to 500 nm nncl even larger nre potentially cl~nà~ing to the eye, althougll the ha3artl clecreases rapiclly with increasing w~velcngell above 500 nm. In tile bancl 200 to 400 nm the mode of action of thc ~otential injury is related to total ~unount of energy delivered to the eye.
Absorbing dyes which completely stop this energy band from penetrating the curtain are available as discussecl later. The mode of action of the band of energy e.~tending from 400 to 500 mn and even larger depends primarily on the energy-density at the retina of the eye. That is, a given amount of energy in the band 400 nm - and - larger, focused on a small spot on the retina of .~ ~ - 3 -the eye, may be n serious hazarcl, ~hile if the snme total amoullt of energy is spread out over a larger spot on thc rctina> it may be to~ally non-hazar(lous, even for e~tended longer-timc vicwing.
Thus, a selective broadening of the image of the minu-te arc spot on the retina, while leaving the diameter of the images of larger Eeatures in the scene relatively unchanged, so that sight and recognition of such features is perceived as "normal", could decrease the hazard below the danger point.
Consequently, the curtain may carry on its surface minute refracting elements, (sometimes called "declivities" herein) conveniently placed there by embossing or by reticulation. Bundles of light rays from the scene pass through the surface. The declivities on the surface ma~e only a very small angle with the surface. The declivities sho-lld preerably be orientecl at random. Thus a bundle of rays from any particulnr point in the scene :is split up into a group of sub-bundles - those whicll passecl through acljacent but ~ifferently orientecl declivities of the curtaill - and are brought to a focus on the retina as a number of partially superimposed images at and surrounding the location where the original image would be ~ere there no declivities. The image of a small arc spot will thereby be spread out on the retina to enlarge its diameter, while the image oE a lnrge Eeature of ~0 the scene - a finger or hallcl or clam~, for e~nlllplc, woulcl bc sl-rencl out -the snllle absolutc amoullt but only a nc~ligible r_lat:ive amoullt nncl so wollld r~taill its neurly llorlllal a~pearance ill the scelle. Ihus tlle llaznrcl-to the eye f~om an overly bright minute source would be negated while still retain-ing satisfactory visual acuity of scenes viewed through the curtain.
rhe net result is that the brightness oE small minute features ~such as an arc spot) is preferentially reduced on the retina, ~hile the brightness and appearance of larger features of the scene is essentially unchanged.
RELATIVE LIGIIT INTENSITY REDUCTION ~SCENE CONTRAST EQUALI~ATION) The normal mechnnism of the h-lmnn eye in pro~ecting itself against a too-bright potentially htlzardous over-illumillation is an involuntary closing of the iris of the eye, and an aversion (of the direction o~ sight) of the eye. Neither of these reactions is effective in the normal circumstance of electric arc-weld scene viewing for persons to be protected by this invention such as adjacent workers, passers-by, and supervisors. This is because the iris responds to the total illumination on the retina, and a very small bright spot surrounded by a dim field of Vie~Y~ is regarded by the eye-brain system as similar to a bright star in a dar~ sky, that is, as a "dar~" scene, and the normal response is a maintainance of a wide-open iris.
The second natural protective mechnnism - the invol~mtary aversion of the eye direction from a bright ligl~t source - is overcome by the con-scious ~Yill of the observer to examine the scene in detail, because it is normally within his l~ork-related duty to see and to study the details of the arc-welding in the scene.
It ~ould, therefore, be desirable to ensure that the iris of the eye will diminish its aperture (pupil) while the arc is in operation.
Thus, the welding curtain may have discontinuities distributed tllroughout the matrix materinl, saicl discontinuities having an optical incle~
of refraction WhiCh differs Erom the optical inclex of refrnction of the material of whicll the curtain is primtlrily mncle by nt let-st 0.2 units, IYl~ere-by to scatter at least 5~ and less than 50% of the light ~Yhich passes through the curtain.
~lost of the light from an arc spot will pass through the protective curtain in such a direction that its light ~Yould not be seen by the eye.
However, a fraction (preferably about one-quarter) of ~his other-directed light is scattered by the curtain, and some part of the scattered light enters the eye from points of tlle curtain removecl from the direct line of sight of the arc ~ith respect to the eye. Tllis scatterecl light from all parts of the curtain is seen by the eye, and forms a general illumination on all parts of the retina. This general illumination, in combination with the residual normal illumination of the rest of the scene, triggers the normal iris -closing response due to a general, ~Yide-spread illumination.
The net result of the scattering feature has been a decrease in scene contrast, that is, a reduction of bright spot intensity and a lightening of the surround, a general field-of-vie~ illumination increase which causes the iris to contract/ and a decrease in the brightness of the image of the arc spot on the retina, since some of the arc spot's brightness has been scattered away in passing througll the curtain.
F UORESCENT WAVELENGTH SHIFTING
It has been pointed out that it is desirable to decrease the amo~mt of potentially harmful short wavelellgtll light penetrating the curtain, and to increase the amount of longer ~Yavelength visible ligllt so that more details of the scene may be clearly seen.
This objective may be accomplished by incorporating a fluorescent dye material in the curtain. ~le characteristic feature of fluorescence is that when a ray (strictly spen~itlg, a ~luantum) o short ~Ynvelengtll light falls upon it, the short wnvelellgtll ligllt mny be totnlly absorbed and all equivalent an~ount of lon~r wnvelQIl~ell ligllt wilL be emittecl in all direc-19~
tions. Thus the incorpor~tion of an appropriately selected fluorescent dye will decrease the amount of shorter wavelength light that penetrates the curtain, thereby further decreasine the hazard to the eye. Furthermore, the newly created fluorescent light, if one chooses a suitu~le fluor 7 will re-emit additional innocuous long-wavelength light, some of which will be re-directed to the whole welding scene, add to the general illunination, and if the fluorescent color is chosen as will be describea, will make its way lm-impeded by the aforementioned sharp cut-off dye (the cut-off chosen to co-operate with the characteristic fluorescently emitted wavelength of the fluorescent dye material) through the curtain to give more visual brightness to the scene surrounding the welding arc.
The welding curtain is preferably made utilizing an organic plastic matrix such as pol~vinylchloride, which itself is opaque to certain undesir-able wavelengths and which can act as a structural support and as a matrix for dyes, pigments, and additives which it may contain~ One or both of its surfaces ca~ be modified to provide the above s~face re~ractive effects~
In the accompanying drawings which illustrate the structures and properties of certain prior art curtains and exemplary embodiments of the present invention:
Figure 1 is a graph showing the inter-relat.ionship between the damage ~unctions of ultraviolet, and of light induced retinal injury "blue-effect" light damage, the transmissivity of a.n ideal cut-off dye, and the photopic eye sensitivity function;
Figure 2 is a graph showing the inter-relationship between the "blue-effect" light damage function curve, the photopic curve, and the trans-missivity behavior of a group of curtains, Figure 3 sho~ls the focusing action of the eye as it looks through a prior art curtain;
-
rllere are thus ttYo m-~eual ly contracl;ctory re(l-lirQIncn-ts ~`or a curtain which allows safe viewing of an electric welding or cutting arc scene. In order to minimize the potential eye hazard, the curtain should stop all wave-lellgths ~rom 200 to 500 or 550 nm or larger. In order to maximize the ability to see the scene, the curtain should pass the maximum of those radiations whicll give rise to the sensation of sight (~00 to 760 nm).
It has been determined as described later, that if the curtain 119'~
transmission cut-off is bet~cen about 500 nm and about 5S0 nm sufficient visible light (witll wavelengtlls betweell about 500 and about 760 nm) will reach the eye, and little enougll residual hazarcll~ill remain, so that such a curtain could constitute a safe and usable welding curtain for passers-by adjacent workers, and supervisors.
Thus, according to the present invention there is provided a curtain for protecting an observer from damage by light from welding arcs, said curtain being sufficiently transparent to see through it an object of sub-stantial size, said curtain comprising:
an organic plastic matrix material which itself is inherently transparent and l~hich is formed into a sheet with a pair of surfaces and a dimension of thickness betl~een said surfaces; and dye distributed throughout said matri~ material, said dye being proviclecl in concentrations which permit the sheet to transmit at least 70~ of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmission of said sheet ~ith dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm.
SPATIAL ~REQUENCY DISCRIMINATION
Radiations from 200 to 500 nm nncl even larger nre potentially cl~nà~ing to the eye, althougll the ha3artl clecreases rapiclly with increasing w~velcngell above 500 nm. In tile bancl 200 to 400 nm the mode of action of thc ~otential injury is related to total ~unount of energy delivered to the eye.
Absorbing dyes which completely stop this energy band from penetrating the curtain are available as discussecl later. The mode of action of the band of energy e.~tending from 400 to 500 mn and even larger depends primarily on the energy-density at the retina of the eye. That is, a given amount of energy in the band 400 nm - and - larger, focused on a small spot on the retina of .~ ~ - 3 -the eye, may be n serious hazarcl, ~hile if the snme total amoullt of energy is spread out over a larger spot on thc rctina> it may be to~ally non-hazar(lous, even for e~tended longer-timc vicwing.
Thus, a selective broadening of the image of the minu-te arc spot on the retina, while leaving the diameter of the images of larger Eeatures in the scene relatively unchanged, so that sight and recognition of such features is perceived as "normal", could decrease the hazard below the danger point.
Consequently, the curtain may carry on its surface minute refracting elements, (sometimes called "declivities" herein) conveniently placed there by embossing or by reticulation. Bundles of light rays from the scene pass through the surface. The declivities on the surface ma~e only a very small angle with the surface. The declivities sho-lld preerably be orientecl at random. Thus a bundle of rays from any particulnr point in the scene :is split up into a group of sub-bundles - those whicll passecl through acljacent but ~ifferently orientecl declivities of the curtaill - and are brought to a focus on the retina as a number of partially superimposed images at and surrounding the location where the original image would be ~ere there no declivities. The image of a small arc spot will thereby be spread out on the retina to enlarge its diameter, while the image oE a lnrge Eeature of ~0 the scene - a finger or hallcl or clam~, for e~nlllplc, woulcl bc sl-rencl out -the snllle absolutc amoullt but only a nc~ligible r_lat:ive amoullt nncl so wollld r~taill its neurly llorlllal a~pearance ill the scelle. Ihus tlle llaznrcl-to the eye f~om an overly bright minute source would be negated while still retain-ing satisfactory visual acuity of scenes viewed through the curtain.
rhe net result is that the brightness oE small minute features ~such as an arc spot) is preferentially reduced on the retina, ~hile the brightness and appearance of larger features of the scene is essentially unchanged.
RELATIVE LIGIIT INTENSITY REDUCTION ~SCENE CONTRAST EQUALI~ATION) The normal mechnnism of the h-lmnn eye in pro~ecting itself against a too-bright potentially htlzardous over-illumillation is an involuntary closing of the iris of the eye, and an aversion (of the direction o~ sight) of the eye. Neither of these reactions is effective in the normal circumstance of electric arc-weld scene viewing for persons to be protected by this invention such as adjacent workers, passers-by, and supervisors. This is because the iris responds to the total illumination on the retina, and a very small bright spot surrounded by a dim field of Vie~Y~ is regarded by the eye-brain system as similar to a bright star in a dar~ sky, that is, as a "dar~" scene, and the normal response is a maintainance of a wide-open iris.
The second natural protective mechnnism - the invol~mtary aversion of the eye direction from a bright ligl~t source - is overcome by the con-scious ~Yill of the observer to examine the scene in detail, because it is normally within his l~ork-related duty to see and to study the details of the arc-welding in the scene.
It ~ould, therefore, be desirable to ensure that the iris of the eye will diminish its aperture (pupil) while the arc is in operation.
Thus, the welding curtain may have discontinuities distributed tllroughout the matrix materinl, saicl discontinuities having an optical incle~
of refraction WhiCh differs Erom the optical inclex of refrnction of the material of whicll the curtain is primtlrily mncle by nt let-st 0.2 units, IYl~ere-by to scatter at least 5~ and less than 50% of the light ~Yhich passes through the curtain.
~lost of the light from an arc spot will pass through the protective curtain in such a direction that its light ~Yould not be seen by the eye.
However, a fraction (preferably about one-quarter) of ~his other-directed light is scattered by the curtain, and some part of the scattered light enters the eye from points of tlle curtain removecl from the direct line of sight of the arc ~ith respect to the eye. Tllis scatterecl light from all parts of the curtain is seen by the eye, and forms a general illumination on all parts of the retina. This general illumination, in combination with the residual normal illumination of the rest of the scene, triggers the normal iris -closing response due to a general, ~Yide-spread illumination.
The net result of the scattering feature has been a decrease in scene contrast, that is, a reduction of bright spot intensity and a lightening of the surround, a general field-of-vie~ illumination increase which causes the iris to contract/ and a decrease in the brightness of the image of the arc spot on the retina, since some of the arc spot's brightness has been scattered away in passing througll the curtain.
F UORESCENT WAVELENGTH SHIFTING
It has been pointed out that it is desirable to decrease the amo~mt of potentially harmful short wavelellgtll light penetrating the curtain, and to increase the amount of longer ~Yavelength visible ligllt so that more details of the scene may be clearly seen.
This objective may be accomplished by incorporating a fluorescent dye material in the curtain. ~le characteristic feature of fluorescence is that when a ray (strictly spen~itlg, a ~luantum) o short ~Ynvelengtll light falls upon it, the short wnvelellgtll ligllt mny be totnlly absorbed and all equivalent an~ount of lon~r wnvelQIl~ell ligllt wilL be emittecl in all direc-19~
tions. Thus the incorpor~tion of an appropriately selected fluorescent dye will decrease the amount of shorter wavelength light that penetrates the curtain, thereby further decreasine the hazard to the eye. Furthermore, the newly created fluorescent light, if one chooses a suitu~le fluor 7 will re-emit additional innocuous long-wavelength light, some of which will be re-directed to the whole welding scene, add to the general illunination, and if the fluorescent color is chosen as will be describea, will make its way lm-impeded by the aforementioned sharp cut-off dye (the cut-off chosen to co-operate with the characteristic fluorescently emitted wavelength of the fluorescent dye material) through the curtain to give more visual brightness to the scene surrounding the welding arc.
The welding curtain is preferably made utilizing an organic plastic matrix such as pol~vinylchloride, which itself is opaque to certain undesir-able wavelengths and which can act as a structural support and as a matrix for dyes, pigments, and additives which it may contain~ One or both of its surfaces ca~ be modified to provide the above s~face re~ractive effects~
In the accompanying drawings which illustrate the structures and properties of certain prior art curtains and exemplary embodiments of the present invention:
Figure 1 is a graph showing the inter-relat.ionship between the damage ~unctions of ultraviolet, and of light induced retinal injury "blue-effect" light damage, the transmissivity of a.n ideal cut-off dye, and the photopic eye sensitivity function;
Figure 2 is a graph showing the inter-relationship between the "blue-effect" light damage function curve, the photopic curve, and the trans-missivity behavior of a group of curtains, Figure 3 sho~ls the focusing action of the eye as it looks through a prior art curtain;
-
3~
Figure 4 shows a vi~w similar to Fi~lre 3, but with the eye seeing throu~h one embodiment of curtain aecordin~ to this invention;
Figure 5 is a vignette showing the left hand surface of the curtain in Figure 4;
Figure 6 is a croæs-section taken at line 6-6 ln Fi~ure 5, Figure 7 shows the field of view and the response of a.~ eye as it looks through a prior art curtain; and Figure 8 shows a view similar to Figure 7, but ~fith the eye seeing through another embodiment of curtain according to this invention.
Figure 1 is a graph illustrating some of the parameters which must be considered in the use of this invention. The abscissa is the wavelength of the radiation in nanometers (nm) while the ordinate is the relative response of the eye to radiation and light and also the relative transmission of cur-tains at the various wavelengths. Graph line 10 shows the ultraviolet radia-tion damage function S. This line discloses that m~xim~ damage is caused by radiation at &bout 270 nanometers.
Still, any radiation whose value is above zero anywhere along -this graph line can cause some damage. For example, at about 225 nanometers the effect is about 1/7 as important as radia-tion at 270 nanometers~ Howe~er, it still constitutes a risk of damage from ultraviolet radiation, although a lesser ris~. The use of ultraviolet absorbers in plastics to absorb the ultraviolet radiation is well-known and no claim is made to absorption of ultraviolet radiation per se. An ultraviolet absorber is conventionally used to preserve the plastic matrix, as ~ell as to prevent transmission of ultra-violet light.
Graph line 11, sho~s the "blue-effect" light hazard function (B).
This graph line shows that retinal damage begins to be caused by radiation above about 400 nm, is maximum at about 440 nm, diminishes as a 9'~
hazard through 600 nm, the hazard remainin6 constant at one thousandth of the maximum value from 600 to 1,400 nm. 'rhe ~reatest risk ls at about l~40 n~.
However, any radiation within the indicated range of sufficient intensity can cause retinal in~ur~.
Graph line 12 is the photopic eye sensitivity function. Th~s sho~s the sensitivity (V) of the eye to visible llght. It rises from a zero value near 400 nm to a maximum at 555 nm and declines to near zero near 760 nm. The more of the light as weighted by this response curve which can be transmitted, the greater uill be the perception to the eye of an ob~ect on the other side of the curtain.
Graph line 13 shows the transmissivity function of a theoretically perfect dye with a "cut-off" at approximately ~91 nanometers. ~t has a rising segment 14. Especially this rising segment, and indeed the whole line, de-fines what the dye will absorb and not pass, and what it will not absorb and will pass. Speaking generally, points beneath and/or to the right of the curve represent transmission. Points above and/or to the left, represent absorption. The rising segment is the area o~ sharpest and greatest effect.
A dye can be theorized, the rising segment of whose curve would be at either a shorter or longer wavelength than the one shown. If it were at a shorter wavelength, it would give slightly more visible energy but would also pass a very significant additional amount of "blue-effect" energy to the hazard of the viewer. Selection of a dye with a rising segment at a longer wavelength would reduce the "blue-effect" light hazard, but woula also diminish the amount of visible light transmitted to the disadvantage of observer visibil-ity. Therefore, there is no perfect dye composition, and certainly no prac-tical dye composition, which will simultaneously entirely eliminate the "blue effect" light hazard and entirely maximize the visible transmission. Accord-ingly, there is a region 15 which is somewhat triangular in shape represent-_ g _ ing "blue-ef~ect" light hazard which will be transmitted even by the theoret-ically perfect curtain.
In Figure 2 there is shown another eraph whose abscissa is wave-length in nanometers and whose ordinate is the relative trans~ission of the curtains (T) and relative response of -the eye (B) and (V). The purpose o~
this graph is to contrast the performance of one represent~tive em~odiment of this invention with some prior art weldine curtains. The prior art cur-tains described have only dyes as their active constituents for the control of light, and there~ore this comparison is made without the above discussed diffracting and scattering e~fects being included.
Graph line 20 shows the relative transmission of a curtain accord-ing to this invention, with dyes only. It will be observed that the curve has a flat segment 21 whose ordinate value is zero between about 200 and about 500 nm, meaning that it -transmits no radiation between these ranges. It then has a rising seg~ent 22, as nearly vertical as can be devised by appropriate dye selection, from about zero transmission to about 80% transmission. Limits 23, 2~ and 24A are respectively shown at 1% at 450 nm, and at 5% at 491 nm, and at 70% at 600 nm. To the right, above about 600 nanometers there is a generally flattened segment 25. This curve indicates that above about 600 nm about 75 to 85 percent of the light of various wavelengths is transmitted by the dyes, which is a very suitable value for a welding curtain.
Region 33 is also shown ~hich indicates the transmission by the curtain Or this invention of residual "blue-effect" light. The absolute effect of the residual "blue-ef~ect" light whose existence i8 indicated in Figure 2 by the somewhat triangular region 33, is obtained by a mathematical weighting process. In each wavelength interval considerea, (e.g. for this invention 500 to 505 nm, 505 to 510 nm, 510 to 515 nm, etc.) the value of the curtain dye transmission ~T) in Figure 2 for segments in the respective line is multip]ied by the value of (B), curve 28 in Figure 2, for the same wave-length interval, and the product multiplied by the value of the spectral radiance of an arc source with a brightness similar -to the sun (L), for the same wavelength interval. The values of the final products (BI,T) thus ob-tained for each wavelength interval are then sum~ed. Thi~ total ~um ~L~, i9 proportional to ~he total "blue-effect" light, hazard to the eye from the residual "blue-effect" light passed by the curtain under consideration. The curtain of this embodiment will be seen to perform in a manner which is rather close to the optimum defined by graph line 13 in Figure 1, although it cannot be expected that any economically priced commerically available dye will be as ideal in its absorption as -the theoretical dye proposed by graph line 13 of Figure 1.
As will be discussed later, a useful method to characterize the relative rating of different curtains in safeguaraing the eye ~d in providing adequate visibility is to compare the ratio of the total amount of visible energy transmitted by a welding curtain ( ~VLT) with the total amount of potentially hazardous "blue-effect" light energy ( ~ B~T) transmitted by the same curtain. The complete description of the method of obtaining the value of the rating factor will take into account the necessary weighing functions such as lines 11 and 12 in Figure 1.
The spectral transmissivity of a curtain is a function of absorptive dyes in the matrix of the curtain. The "percei~ed" color is not to be con-fused with "spectral" color, even though the various curtains described do have a "color" which is perceived by the user. One refers herein to trans-mission and to cut-off strictly as a function of wavelength.
Assuming a suitable dye a useful curtain can be obtained, but such a curtain continues to in~olve the transmission of "blue-effect" light to the hazard of the observer. One problem with this "blue-effect" light is that l~L'hl~
the eyeball is not strongl~ reactive to it. The ligh-t which constitutes the "blue-effect" light hazard can have wavelengths longer or shorter than that of the spectra] color blue. The perceived color blue does, however, charac-terize the color sensed in this region. There is little pain or other een~a-tion from it, and damage CQn be done because no protective action ~rill be taken. This damage is a function of energy per unit area incident on the retina. In a welding operation, it comes from a small source to which the pupil will not be adequa-tely reactive? but tbe light is strongly focused by the eye, and this increases the area loading.
One technique to assist and instruct the eye f'or its own protec tion is shown in Figure ~, where a curtain 35 having a pair of surf'aces 36, 37 is sho~n disposed between the eye 38 of' an observer and a welding opera-tion 39. The welding operation is indicated by schematic welding rod 4O
adjacent to a workpiece 41 and generating a fireball (arc) 2l2 which is the source of the light being protected against herein. The lens 43 of the eye is focused on a retina 44. ~n iris 45 forms a variable aperture to determine the amount of light which enters the eye through an area called the pupil.
~lore light is admitted when it is enlarged than ~hen it is constricted.
Primary rays 46, 47 are shown impinging on a curtain 35.
A similar view is shown in Figure 3, where the same ra~s impinge on a prior art curtain 49. The prior art curtain ;s dyed but transparent, and has two smooth parallel surfaces 5O, 51. In Figure 3, rays 461 47 are imaged by the lens to form a central image 52 whose relative size is shown in solid oval line immediately ad~acent to the retina.
In order to reduce the unit loading on the retina it is usef~l to spread the light as much as possible for the ~ame pupil area opening. In -the embodiment illustrated in Figure 4 this is accomplished by reticulated or embossed declivities 53 on surfaces 54 as shown in Figures 4 6. ~he purpose of t~e~e variations from a planar surface is to provide sur-race-refractive spreadirlg of the beam. Thls will spread the image and reduce the unit load-ing.
For purposes of disclosure, dimpled declivities are sho~m, and their dimensions are greatly e~a~gerated. For purposes of the fol1owing specific example, the size of the ~ireball 112 is taken -to be 6mm dia~leter, the distance from fireball 42 to curtain 35 or 49 is taken to ~e 1.3m, and the distance from the curtain to the eye 38 of the observer, is also 1.3m.
In general it is preferred that the tangents to the surfaces of the declivities do not exceed a difference greater than about 8 minutes of arc from parallelism with what would be s~ooth planar surface parallel to surface 54. This is sho~m by angle 51~a (Figure 6). Such an arran~ement will give an image change corresponding to about a 4 minute of arc divergence on each side of the image of any ob~ect in the field of view. Such image en-largement is a considerable part of the size of the otherwise unspread arc spot image size. Indeed for the dimensions ~uoted the effect is to about quadruple the area on uhich the energy falls even though a brighter portion is still loca-ted in the center. The enlarged areas are shown as areas 55, 56, 57, 58 in Figure 4. This provides a gross enlargement in the image and spaces out the image rather similar to a range finder. The additional en-largement due to the 4 minutes of axc divergence on each side o~ a larger object of say 32 minutes of arc (a 25 mm obJect) will only raise the image size to that corresponding to an image appropriate to a 30 mm object. The 25 mm object would still be clearly recognizable. Even a smaller amount of spreading ofthe incident rays causes a substantial reduction in unit loading on the retina. The effect this surface treatment has on arc image intensity on the retina is described later. For simplification of the optical effect the declivities have been shown on one side only. Declivnties with half the -9~
angle ~4 minutes of arc) and of the same size on both sides of the curtain would have nearly the same effect.
The sllrface treatment irregularity can be provlded in many ways.
One way is to calendar a pattern all over the surface, and this wlll produc~
predetermined shape~, which could be defined by planes to ~orm pyramid~ and the like. Instead of sharp and planar bounded declivitie6, these may instead be dimpled structures with curved boundaries, conveniently provided as an "orange peel" surface kno~n to all persons accustomed to calendaring sheets of polyvinylchloride as the consequence of reticulation. Such a surface is shown in Figures 5 and 6, wherein the plurality of dimple-shaped concave declivities 53 are formed in the surface 5~, as already described. The same criteria would apply to other types of surface irregulalities, al] of which are for convenience ca-led "declivities", even though they may be convexly or concavely planar or curved in contour. It is not desirable to diffuse -the image too greatly. The extent shown is optimum.
If a greater angle is chosen, the images of larger ob~ects are spread too much to be seen. If the declivities are too large (over a few millimeter in size) the image o~ the arc is not divided into parts and so it can not be spread. If the declivities are too small (much less than a milli-meter) they tend to scatter light instead of slightly redirecting -the bundles of light. This would obscure the scene behind the curtain. Therefore the average declivity ought not to exceed about 1 mm across, and may be smaller.
Another technique to reduce the intensity of the image depends on in-body scattering, wherein about 25~ of the light is likely to be scattered, and about 67% (the remaining 8% is due to surface reflection) will pass through without any scattering at all to form an image. ~his class of scattering causes light from the arc to appear to come from the curtain itself. The curtain therefore becomes brighter, and this reduces the con-trast between the background and the bright arc, while at the same time itprovides illumination ~rhich causes the pupil to constrict. Materials for scattering are index of refraction discontinuities which may be part:lculates or voids whose index o~ rePraction is dif~erent from that of the n~l~,rlx material. The preser.tly preferred materials are fluorescent ~,inc oxide, zinc oxide, and titanium dioxide, ~11 o~ whose indicies of refraction are above 2Ø ~he index of refraction of polyvinylchloride is about 1.5. Sim-ilarly, air may be utilized, being incorporated in the matrix as bubbles.
The index of refraction of air is 1Ø It is desirable for there to be a difference in index of refraction between matrix and discontinuity of at least about 0.2 for best results.
This type of scattering will cause every part of curtain 59 (Fig-l~e 8) to scatter light into the eye 38. In Figure 8, curtain 59 is shown with the surface treatment of curtain 35 o~ Figure ~, and this is the pre-ferred embodiment. However, the surface treatment is ignored in Figure 8 for clarity in describing other features of the invention.
The result of the in-body scattering is that the scene perceived consists of a lower contrast (and about 25% lower arc-image intensity is the best embodiment) fireball against a relatively brighter (about four times more light appears to be emitted by -the curtain itsel~, compared with prior art curtains without this feature~ backgro~md. Such scat-tering centers of the type mentioned tend to preferentially scatter the wavelengths which approx-imate their own size. Accordingly, for the purpose of scattering wavelengths of light which pass through the curtain, particulates or other discontinuities on the order of about 500 nm in si~e should be utilized.
This class of scattering is shown in Figure 8 where visible light (including the ~blue-effect~' light) is shown as ray 70 impinging on discon-tinuities 71. Some of the visible light rays ~ill of course pass direct~
9~
through the curtain, but some rays will be scattered through the observer1s side of the curtain &s sho~m by ~catter rays 73 and 7~.
Such scatter rays o~ course occur over the entire sur~Dce and those scattered in the direction of the eye such as ray 75 are collectea by the pupil. Rays such a~ ray 7~ may pass unscattered through the curtain direc-tl~
to the eye. To the extent that scattered rays such as rays 73 and 7ll, and some rays which are scatterea reversely such as rays 76, 77 and 78, remove energy from the beam, ~hey cause a diminution (about 25% reduction in the preferred embodiment) in the intensity of the beam which forms -the image of the arc spot on the retina of the eye. The decreased intensity of the image of the arc spot formed on the retina represents a decreased hazard from the residual "blue-effect" lieht component of the ra~.
r~hose forward-scattered rays such as ray 75 that happen to be directed precisely toward the eye, will be focused on the retina at places on the retina removed from the location of the image of the arc spot 79, that is, they will be focused at about, or near 80 on the retina, and of course this is a wide-area effect from the entire surface of the curtain. Such in-creased brightness in all of the curtain acting as a background and pro~ecting light to the retina over a wider area causes the irîs to contract its diam-eter, still further diminishing the energy ~ocused on spot 79 from the arcspot. ~his results in a further diminution (about 30% reduction due to iris constriction in the pre~erred embodiment) of the hazard from the residual "blue-effectt' light component of the light from the a~c spot.
Similarly, rearward reflected scattered light shown by rays 76, 77 and 78 is directed into the region of the welding operation. There it may have struck some ob~ect 80, (ray 78 does this) and then have been returned as ray 81 through the curtain to the pupil, of course ray 81 may undergo some scattering itself. Rays 78 will ~id in illuminating the booth, ana the ~ 16 -reflected ray ~1 reaching the retina will further cause the iris to decrease its diameter with berle~icial results as Just described (as much as 5% reduc-tion due to iris constriction depending on the reflective nature of obJects in -the booth).
Still another meana to protect the eye i3 -to pro~ide ~ ~luorescent dye in the curtain which is responsive to the ultrlwiolet radiation. ~tra-violet radiation will not pass through the cuxtain, but when an ultraviolet ray 85 impinges on a fluorescent dye particle 86 in the curtain, the energy of the ray will be converted to visible fluorescent light shown by rays 87-92.
Forwardly extending rays 87-ô9 behave in much the same manner as rays 73-75 by illuminating the curtain and making it brighter so as to instruct the eye--brain system to constrict the pupil, thereby to decrease the a~ount of enersy which passes through the lens ~nd onto the retina. ~his augments the effect of the scattering o~ light described above in diminishing the "blue-effect"
light hazard from the focused arc spot on the retina. This ef~ect can further reduce the apparent brightness Or the arc spot by an additional 5%.
Similarly some fluorescent light will be emitted back into the ~ork area (rays 90, 91, 92), strike an obJect 93 and be reflected by it as reflected ray 94 which can also reach the eye.
Dimension 95 indicates a constricted pupil caused by the constric-tion of the iris due to this additional light.
The fluorescent dye is responsive only when it is near (a few microns from) the snrface because the ultraviolet absorber, present for another purpose, would absorb all the ultraviolet radiation that would stim-ulate the fluorescent dye. The fluorescent dye's response to ultraviolet stimulation is decreased with use, and as such must be continuously replen-ished at the surface. This is accomplished by using a mobile dye which diffuses through the body of the curtains and therefore allows fresh flores-.~
119'~
cent dye to appear near the surtace as the existing dye is exhausted.
Figure 7 shows a prior art arrangement with a welding set-up and a conventional curtain 100 having only a dye and smoo-th surfacos 101, 102. It is shown passing light 103 above about 350 nm and stopping ultravlolet rays 104 and also passing visible llght 105 in various directions. rrhere is nothing to light up the curtain, so the iris remains unconstricted, as shown by dimension 107. Nothing is done to enlarge the image of the arc spot on the retina. For the same condition of relative location of arc, curtain and observer and for the same initial arc spot intensity, the potential "blue effect" light ha3ard is always greater than for a curtain according to this invention.
Referring to Figure 1, graph line 13 shows the characteristics of a dye whose transmissivity i8 0 from 200 nm to the cut-o~f wavelength ~ , shown for example as 500 nm in the figure (segment 14); and whose transmis-sivity changes abruptly at ~ to 100% transmissivity from 500 -to 1,400 nm.
On ex~mining the changes in the relative values of graph lines 11 and 12 in Figure 1 in the vicinity of the cut-off wavelength, it is clear that if the cut-off wavelength were chosen as somewhat less th~n 500 nm, the contribution of "blue-effect" light (line 11) would increase proportionately much more rapidly than the contribution of visible ligbt (line 12~ would decrease. Conversely, if the cut-off were chosen at slightly larger wave-lengths than 500 nm, the contribution of "blue-effect" light would decrease proportionately much less than the contribution o~ visible light would in-crease.
Hence, the cut-off for a curtain dye should be chosen as far to the left in Figure 1 as is consistent with yielding an acceptable stare time for the use intended.
While the perfect cut-off filter ~one in which the transmission changes from 0 to 100% completely at a given wavelength as in seement 14, Figure 1) is not physically attainable, cut-off fi]ters c~ be made whose trar,sition is sufficiently sharp, and whose transition from relatively opaque to relatively transparent takes place over a n~lrxow waveleTIgtll ~and. A
desirable example of such filters has a characteristic shown in Flgure 2 as line 20. It will be noted that the segment 22 of r~pid rise is rea~onably near to vertical, and that the cut-off' "foot~ 100 reduces the ~'blue-effect"
better than any of the "prior art't curtains whose spectra are shown in T~'igure 2, and in which the "foot" is not minimized.
A most desirsble dye would have its most nearly vertical segment corresponding to segment 14 in Figure 1 displaced f'rom 491 nm, and wol~d have as sharp a cut-off as possible on the shorter wavelength side, màrked 103 in Figure 1. The sharp cut-off at the foot is far more important than a sharp cut-off at the high transmission end of the transition, marked 102, since for a real curtain dye the unavoidable slope of the segment correspond-ing to segment 14 in Figure 1, or segment 22 in Figure 2 has carried the long wavelength shoulder far to the right of the wavelength 491 nm. The additional contribution to hazard from blue light (B, Figure 1, line 11) at the top cut-off wavelength is very small; the change in luminous ef'~ect depending on V
(Figure 1, line 12) is proportionally not great.
The consequence o~ this analysis is that the most use~ul d~es for the curtains under consideration must have a steep rise (compare segment 14 in ~igure 1), a sharp foot (compare foot 100 in Figure 2), and the steep rise should take place at a wavelength removed from 491 nm. The last part of' the requirement comes about since the sensitivity o~ the ratio ~VLT/~BLT is greatest at 491 nm, relatively slight changes in the concentration of the dye in the curtain, and hence in the transmissivity, will shi~t the value ~VLT/~BLT unacceptably due to unavoidable manufac-turing process variations.
- 19 ~
"L" represents the spectral radiance of the source.
A description of a dye for optimum curtain manufacture i8 best done by specifying design points in the curve of Figure 2.
The transmission vs wavelength curve (~igures 1 and 2) should have limits as follows:
Limit 23: at 450 nm, the relative transmission should not be greater than 0.01 (1%).
Limit 24: at 491 nm~ the relative transmission should not be greater than 0.05 (5%).
Limit 24a: at 600 nm, the relative transmission should be at least (70~).
This relates only to an organic plastic matrix with dye, with smooth surfaces, and without any scattering function. These additional functions will improve the curtain even without the optimum dyes. Figures 1 and 2 illustrate only the dye's function.
Control and variation of permissible stare time i5 accompli~hed by means of the following procedures.
I. SPECTR L_ PACE DISCRIMINATION
The dye composition and concentration is varied so that the segment corresponding to line 14 in Figure 1 is displaced sensibly parallel to it-self, but to the right or left.
II. SPATIAL FREQUENCY DISTRIBUTION
Surface refraction is used to preferentially reduce the brightness of the image of the small arc spot on the retina, and therefore decrease the sum ~BLT on the retina, while leaving the intensity of large features of the scene sensibly unchanged.
III. FEATURES OF SCBNE CONTRAST EQUALIZATION
Surface and volume scattering reduce the value of LLT and ~LT~ and h cause th~ curtain to scatter light to the general field of view. l'his causes the iris to contract and diminishes the ~ize of the pupil of the eye, and BO
the energy delivered to the retina at the lmage location of the arc æpot :Ls further diminished.
IV. FEA~URES OF_FLUORESCE~T ~IAVELENGTH SHIFTING
This will add to the illumination of the ~cene, further reducine the size of the pupil, hence the energy aelivered to the retina at the image location of the arc spot is further diminished. On the other hand, the value of VL~ will be increased because some of the fluorescent light falls on the scene and increases the ~eneral visible-light level by which features of the scene are seen. This last factor can offset some or all of the loss of ~VLT
caused by scatterine discussed in III directly above, but it does not change the effect of III in diminishing ~BLT.
In Table I there is shown a list of materials of construction with which it is possible to make the best known mode of curtain, and also to make curtains of lesser but still adequate performance, and to make some advan-tages of the invention available even in curtains having dyes which do not function according to the criteria of this invention.
In describing the dyes, considerable difficulty is encountered, because their compositions tend to be regarded by their manufacturers as trade æecrets. In general, metallic azo dyes, a well-known type of dye, are preferred for their stability. Curtains with such dyes should last a con-siderable time without undue fading, because metallic azo dyes are quite resistant to fading. However, any type of dye with a suit&ble cut-off in accordance with meeting the criteria of this invention, can be used instead of the exemplar~- dyes disclosed herein.
As to the scattering materials, their size is selected to approx-imate the wavelength preferentially to be scattered. ~he most appropriate - 21 ~
materials are any o~ the following: air bubbles, zinc oxide powder, ~luo-rescent zinc oxide powder, titanium dioxide powder, or mixtures of them~
Fluorescent zinc oxide performs a dual function of both scattering and fluorescing.
The fire retardant is selected in addition to ita ~a~or Pun~tion, for having an optic~l lndex of' refraction nearly equal to -k'hat Or -the base polymer. Then the mixture is as transparent as the ma-trix.
The organic plastic matrix is preferably polyvinylc'hloride. It works well, is well-understood, and has a suitable life. Of course other transparent organic plastic materials could be used instead. Pol~vinyl-chloride is given merely as an example of a large number of sui-table mate-rials.
The plasticizers will be those known in the art for use with the selected matrix material.
Ultraviolet absorbers are well-kno~n, and need no detailed descrip-tion here.
BEST MODE CURTAIN (with reference to Table I). Percentages are by weight and are approximate~
The identified "Base Polymer": 41%
DOP plasticizer : 41%
The metallic azo dye identified as Sc-39-3 s/s bright orange : 1-1/3%
The fluorescent orange dye identified as C507XX Product No. 40-26-2 : 1/2%
The identified fluorescent zinc oxide phosphor, particle size about 500 nm : 0.17%
The identified W absorber : 1%
Theidentified fire reterdant : 15%
This curtain will be provided with declivities on both of its surfaces, produced by reticulation.
OTHER CU~TAINS:
1. The "2nd choice" f`luorescent orange dye may be subs-tituted for ~he fluorescent dye in the best mode cur-tain.
2. The "2nd choice" pigment (titanium dioxide), zinc ox-lde~ or air bubbles of the same size, may be substituted ~`or the iluorescent zinc oxiae.
3. Dioctyl azelate may be substituted -for the DOP plasticizer.
Figure 4 shows a vi~w similar to Fi~lre 3, but with the eye seeing throu~h one embodiment of curtain aecordin~ to this invention;
Figure 5 is a vignette showing the left hand surface of the curtain in Figure 4;
Figure 6 is a croæs-section taken at line 6-6 ln Fi~ure 5, Figure 7 shows the field of view and the response of a.~ eye as it looks through a prior art curtain; and Figure 8 shows a view similar to Figure 7, but ~fith the eye seeing through another embodiment of curtain according to this invention.
Figure 1 is a graph illustrating some of the parameters which must be considered in the use of this invention. The abscissa is the wavelength of the radiation in nanometers (nm) while the ordinate is the relative response of the eye to radiation and light and also the relative transmission of cur-tains at the various wavelengths. Graph line 10 shows the ultraviolet radia-tion damage function S. This line discloses that m~xim~ damage is caused by radiation at &bout 270 nanometers.
Still, any radiation whose value is above zero anywhere along -this graph line can cause some damage. For example, at about 225 nanometers the effect is about 1/7 as important as radia-tion at 270 nanometers~ Howe~er, it still constitutes a risk of damage from ultraviolet radiation, although a lesser ris~. The use of ultraviolet absorbers in plastics to absorb the ultraviolet radiation is well-known and no claim is made to absorption of ultraviolet radiation per se. An ultraviolet absorber is conventionally used to preserve the plastic matrix, as ~ell as to prevent transmission of ultra-violet light.
Graph line 11, sho~s the "blue-effect" light hazard function (B).
This graph line shows that retinal damage begins to be caused by radiation above about 400 nm, is maximum at about 440 nm, diminishes as a 9'~
hazard through 600 nm, the hazard remainin6 constant at one thousandth of the maximum value from 600 to 1,400 nm. 'rhe ~reatest risk ls at about l~40 n~.
However, any radiation within the indicated range of sufficient intensity can cause retinal in~ur~.
Graph line 12 is the photopic eye sensitivity function. Th~s sho~s the sensitivity (V) of the eye to visible llght. It rises from a zero value near 400 nm to a maximum at 555 nm and declines to near zero near 760 nm. The more of the light as weighted by this response curve which can be transmitted, the greater uill be the perception to the eye of an ob~ect on the other side of the curtain.
Graph line 13 shows the transmissivity function of a theoretically perfect dye with a "cut-off" at approximately ~91 nanometers. ~t has a rising segment 14. Especially this rising segment, and indeed the whole line, de-fines what the dye will absorb and not pass, and what it will not absorb and will pass. Speaking generally, points beneath and/or to the right of the curve represent transmission. Points above and/or to the left, represent absorption. The rising segment is the area o~ sharpest and greatest effect.
A dye can be theorized, the rising segment of whose curve would be at either a shorter or longer wavelength than the one shown. If it were at a shorter wavelength, it would give slightly more visible energy but would also pass a very significant additional amount of "blue-effect" energy to the hazard of the viewer. Selection of a dye with a rising segment at a longer wavelength would reduce the "blue-effect" light hazard, but woula also diminish the amount of visible light transmitted to the disadvantage of observer visibil-ity. Therefore, there is no perfect dye composition, and certainly no prac-tical dye composition, which will simultaneously entirely eliminate the "blue effect" light hazard and entirely maximize the visible transmission. Accord-ingly, there is a region 15 which is somewhat triangular in shape represent-_ g _ ing "blue-ef~ect" light hazard which will be transmitted even by the theoret-ically perfect curtain.
In Figure 2 there is shown another eraph whose abscissa is wave-length in nanometers and whose ordinate is the relative trans~ission of the curtains (T) and relative response of -the eye (B) and (V). The purpose o~
this graph is to contrast the performance of one represent~tive em~odiment of this invention with some prior art weldine curtains. The prior art cur-tains described have only dyes as their active constituents for the control of light, and there~ore this comparison is made without the above discussed diffracting and scattering e~fects being included.
Graph line 20 shows the relative transmission of a curtain accord-ing to this invention, with dyes only. It will be observed that the curve has a flat segment 21 whose ordinate value is zero between about 200 and about 500 nm, meaning that it -transmits no radiation between these ranges. It then has a rising seg~ent 22, as nearly vertical as can be devised by appropriate dye selection, from about zero transmission to about 80% transmission. Limits 23, 2~ and 24A are respectively shown at 1% at 450 nm, and at 5% at 491 nm, and at 70% at 600 nm. To the right, above about 600 nanometers there is a generally flattened segment 25. This curve indicates that above about 600 nm about 75 to 85 percent of the light of various wavelengths is transmitted by the dyes, which is a very suitable value for a welding curtain.
Region 33 is also shown ~hich indicates the transmission by the curtain Or this invention of residual "blue-effect" light. The absolute effect of the residual "blue-ef~ect" light whose existence i8 indicated in Figure 2 by the somewhat triangular region 33, is obtained by a mathematical weighting process. In each wavelength interval considerea, (e.g. for this invention 500 to 505 nm, 505 to 510 nm, 510 to 515 nm, etc.) the value of the curtain dye transmission ~T) in Figure 2 for segments in the respective line is multip]ied by the value of (B), curve 28 in Figure 2, for the same wave-length interval, and the product multiplied by the value of the spectral radiance of an arc source with a brightness similar -to the sun (L), for the same wavelength interval. The values of the final products (BI,T) thus ob-tained for each wavelength interval are then sum~ed. Thi~ total ~um ~L~, i9 proportional to ~he total "blue-effect" light, hazard to the eye from the residual "blue-effect" light passed by the curtain under consideration. The curtain of this embodiment will be seen to perform in a manner which is rather close to the optimum defined by graph line 13 in Figure 1, although it cannot be expected that any economically priced commerically available dye will be as ideal in its absorption as -the theoretical dye proposed by graph line 13 of Figure 1.
As will be discussed later, a useful method to characterize the relative rating of different curtains in safeguaraing the eye ~d in providing adequate visibility is to compare the ratio of the total amount of visible energy transmitted by a welding curtain ( ~VLT) with the total amount of potentially hazardous "blue-effect" light energy ( ~ B~T) transmitted by the same curtain. The complete description of the method of obtaining the value of the rating factor will take into account the necessary weighing functions such as lines 11 and 12 in Figure 1.
The spectral transmissivity of a curtain is a function of absorptive dyes in the matrix of the curtain. The "percei~ed" color is not to be con-fused with "spectral" color, even though the various curtains described do have a "color" which is perceived by the user. One refers herein to trans-mission and to cut-off strictly as a function of wavelength.
Assuming a suitable dye a useful curtain can be obtained, but such a curtain continues to in~olve the transmission of "blue-effect" light to the hazard of the observer. One problem with this "blue-effect" light is that l~L'hl~
the eyeball is not strongl~ reactive to it. The ligh-t which constitutes the "blue-effect" light hazard can have wavelengths longer or shorter than that of the spectra] color blue. The perceived color blue does, however, charac-terize the color sensed in this region. There is little pain or other een~a-tion from it, and damage CQn be done because no protective action ~rill be taken. This damage is a function of energy per unit area incident on the retina. In a welding operation, it comes from a small source to which the pupil will not be adequa-tely reactive? but tbe light is strongly focused by the eye, and this increases the area loading.
One technique to assist and instruct the eye f'or its own protec tion is shown in Figure ~, where a curtain 35 having a pair of surf'aces 36, 37 is sho~n disposed between the eye 38 of' an observer and a welding opera-tion 39. The welding operation is indicated by schematic welding rod 4O
adjacent to a workpiece 41 and generating a fireball (arc) 2l2 which is the source of the light being protected against herein. The lens 43 of the eye is focused on a retina 44. ~n iris 45 forms a variable aperture to determine the amount of light which enters the eye through an area called the pupil.
~lore light is admitted when it is enlarged than ~hen it is constricted.
Primary rays 46, 47 are shown impinging on a curtain 35.
A similar view is shown in Figure 3, where the same ra~s impinge on a prior art curtain 49. The prior art curtain ;s dyed but transparent, and has two smooth parallel surfaces 5O, 51. In Figure 3, rays 461 47 are imaged by the lens to form a central image 52 whose relative size is shown in solid oval line immediately ad~acent to the retina.
In order to reduce the unit loading on the retina it is usef~l to spread the light as much as possible for the ~ame pupil area opening. In -the embodiment illustrated in Figure 4 this is accomplished by reticulated or embossed declivities 53 on surfaces 54 as shown in Figures 4 6. ~he purpose of t~e~e variations from a planar surface is to provide sur-race-refractive spreadirlg of the beam. Thls will spread the image and reduce the unit load-ing.
For purposes of disclosure, dimpled declivities are sho~m, and their dimensions are greatly e~a~gerated. For purposes of the fol1owing specific example, the size of the ~ireball 112 is taken -to be 6mm dia~leter, the distance from fireball 42 to curtain 35 or 49 is taken to ~e 1.3m, and the distance from the curtain to the eye 38 of the observer, is also 1.3m.
In general it is preferred that the tangents to the surfaces of the declivities do not exceed a difference greater than about 8 minutes of arc from parallelism with what would be s~ooth planar surface parallel to surface 54. This is sho~m by angle 51~a (Figure 6). Such an arran~ement will give an image change corresponding to about a 4 minute of arc divergence on each side of the image of any ob~ect in the field of view. Such image en-largement is a considerable part of the size of the otherwise unspread arc spot image size. Indeed for the dimensions ~uoted the effect is to about quadruple the area on uhich the energy falls even though a brighter portion is still loca-ted in the center. The enlarged areas are shown as areas 55, 56, 57, 58 in Figure 4. This provides a gross enlargement in the image and spaces out the image rather similar to a range finder. The additional en-largement due to the 4 minutes of axc divergence on each side o~ a larger object of say 32 minutes of arc (a 25 mm obJect) will only raise the image size to that corresponding to an image appropriate to a 30 mm object. The 25 mm object would still be clearly recognizable. Even a smaller amount of spreading ofthe incident rays causes a substantial reduction in unit loading on the retina. The effect this surface treatment has on arc image intensity on the retina is described later. For simplification of the optical effect the declivities have been shown on one side only. Declivnties with half the -9~
angle ~4 minutes of arc) and of the same size on both sides of the curtain would have nearly the same effect.
The sllrface treatment irregularity can be provlded in many ways.
One way is to calendar a pattern all over the surface, and this wlll produc~
predetermined shape~, which could be defined by planes to ~orm pyramid~ and the like. Instead of sharp and planar bounded declivitie6, these may instead be dimpled structures with curved boundaries, conveniently provided as an "orange peel" surface kno~n to all persons accustomed to calendaring sheets of polyvinylchloride as the consequence of reticulation. Such a surface is shown in Figures 5 and 6, wherein the plurality of dimple-shaped concave declivities 53 are formed in the surface 5~, as already described. The same criteria would apply to other types of surface irregulalities, al] of which are for convenience ca-led "declivities", even though they may be convexly or concavely planar or curved in contour. It is not desirable to diffuse -the image too greatly. The extent shown is optimum.
If a greater angle is chosen, the images of larger ob~ects are spread too much to be seen. If the declivities are too large (over a few millimeter in size) the image o~ the arc is not divided into parts and so it can not be spread. If the declivities are too small (much less than a milli-meter) they tend to scatter light instead of slightly redirecting -the bundles of light. This would obscure the scene behind the curtain. Therefore the average declivity ought not to exceed about 1 mm across, and may be smaller.
Another technique to reduce the intensity of the image depends on in-body scattering, wherein about 25~ of the light is likely to be scattered, and about 67% (the remaining 8% is due to surface reflection) will pass through without any scattering at all to form an image. ~his class of scattering causes light from the arc to appear to come from the curtain itself. The curtain therefore becomes brighter, and this reduces the con-trast between the background and the bright arc, while at the same time itprovides illumination ~rhich causes the pupil to constrict. Materials for scattering are index of refraction discontinuities which may be part:lculates or voids whose index o~ rePraction is dif~erent from that of the n~l~,rlx material. The preser.tly preferred materials are fluorescent ~,inc oxide, zinc oxide, and titanium dioxide, ~11 o~ whose indicies of refraction are above 2Ø ~he index of refraction of polyvinylchloride is about 1.5. Sim-ilarly, air may be utilized, being incorporated in the matrix as bubbles.
The index of refraction of air is 1Ø It is desirable for there to be a difference in index of refraction between matrix and discontinuity of at least about 0.2 for best results.
This type of scattering will cause every part of curtain 59 (Fig-l~e 8) to scatter light into the eye 38. In Figure 8, curtain 59 is shown with the surface treatment of curtain 35 o~ Figure ~, and this is the pre-ferred embodiment. However, the surface treatment is ignored in Figure 8 for clarity in describing other features of the invention.
The result of the in-body scattering is that the scene perceived consists of a lower contrast (and about 25% lower arc-image intensity is the best embodiment) fireball against a relatively brighter (about four times more light appears to be emitted by -the curtain itsel~, compared with prior art curtains without this feature~ backgro~md. Such scat-tering centers of the type mentioned tend to preferentially scatter the wavelengths which approx-imate their own size. Accordingly, for the purpose of scattering wavelengths of light which pass through the curtain, particulates or other discontinuities on the order of about 500 nm in si~e should be utilized.
This class of scattering is shown in Figure 8 where visible light (including the ~blue-effect~' light) is shown as ray 70 impinging on discon-tinuities 71. Some of the visible light rays ~ill of course pass direct~
9~
through the curtain, but some rays will be scattered through the observer1s side of the curtain &s sho~m by ~catter rays 73 and 7~.
Such scatter rays o~ course occur over the entire sur~Dce and those scattered in the direction of the eye such as ray 75 are collectea by the pupil. Rays such a~ ray 7~ may pass unscattered through the curtain direc-tl~
to the eye. To the extent that scattered rays such as rays 73 and 7ll, and some rays which are scatterea reversely such as rays 76, 77 and 78, remove energy from the beam, ~hey cause a diminution (about 25% reduction in the preferred embodiment) in the intensity of the beam which forms -the image of the arc spot on the retina of the eye. The decreased intensity of the image of the arc spot formed on the retina represents a decreased hazard from the residual "blue-effect" lieht component of the ra~.
r~hose forward-scattered rays such as ray 75 that happen to be directed precisely toward the eye, will be focused on the retina at places on the retina removed from the location of the image of the arc spot 79, that is, they will be focused at about, or near 80 on the retina, and of course this is a wide-area effect from the entire surface of the curtain. Such in-creased brightness in all of the curtain acting as a background and pro~ecting light to the retina over a wider area causes the irîs to contract its diam-eter, still further diminishing the energy ~ocused on spot 79 from the arcspot. ~his results in a further diminution (about 30% reduction due to iris constriction in the pre~erred embodiment) of the hazard from the residual "blue-effectt' light component of the light from the a~c spot.
Similarly, rearward reflected scattered light shown by rays 76, 77 and 78 is directed into the region of the welding operation. There it may have struck some ob~ect 80, (ray 78 does this) and then have been returned as ray 81 through the curtain to the pupil, of course ray 81 may undergo some scattering itself. Rays 78 will ~id in illuminating the booth, ana the ~ 16 -reflected ray ~1 reaching the retina will further cause the iris to decrease its diameter with berle~icial results as Just described (as much as 5% reduc-tion due to iris constriction depending on the reflective nature of obJects in -the booth).
Still another meana to protect the eye i3 -to pro~ide ~ ~luorescent dye in the curtain which is responsive to the ultrlwiolet radiation. ~tra-violet radiation will not pass through the cuxtain, but when an ultraviolet ray 85 impinges on a fluorescent dye particle 86 in the curtain, the energy of the ray will be converted to visible fluorescent light shown by rays 87-92.
Forwardly extending rays 87-ô9 behave in much the same manner as rays 73-75 by illuminating the curtain and making it brighter so as to instruct the eye--brain system to constrict the pupil, thereby to decrease the a~ount of enersy which passes through the lens ~nd onto the retina. ~his augments the effect of the scattering o~ light described above in diminishing the "blue-effect"
light hazard from the focused arc spot on the retina. This ef~ect can further reduce the apparent brightness Or the arc spot by an additional 5%.
Similarly some fluorescent light will be emitted back into the ~ork area (rays 90, 91, 92), strike an obJect 93 and be reflected by it as reflected ray 94 which can also reach the eye.
Dimension 95 indicates a constricted pupil caused by the constric-tion of the iris due to this additional light.
The fluorescent dye is responsive only when it is near (a few microns from) the snrface because the ultraviolet absorber, present for another purpose, would absorb all the ultraviolet radiation that would stim-ulate the fluorescent dye. The fluorescent dye's response to ultraviolet stimulation is decreased with use, and as such must be continuously replen-ished at the surface. This is accomplished by using a mobile dye which diffuses through the body of the curtains and therefore allows fresh flores-.~
119'~
cent dye to appear near the surtace as the existing dye is exhausted.
Figure 7 shows a prior art arrangement with a welding set-up and a conventional curtain 100 having only a dye and smoo-th surfacos 101, 102. It is shown passing light 103 above about 350 nm and stopping ultravlolet rays 104 and also passing visible llght 105 in various directions. rrhere is nothing to light up the curtain, so the iris remains unconstricted, as shown by dimension 107. Nothing is done to enlarge the image of the arc spot on the retina. For the same condition of relative location of arc, curtain and observer and for the same initial arc spot intensity, the potential "blue effect" light ha3ard is always greater than for a curtain according to this invention.
Referring to Figure 1, graph line 13 shows the characteristics of a dye whose transmissivity i8 0 from 200 nm to the cut-o~f wavelength ~ , shown for example as 500 nm in the figure (segment 14); and whose transmis-sivity changes abruptly at ~ to 100% transmissivity from 500 -to 1,400 nm.
On ex~mining the changes in the relative values of graph lines 11 and 12 in Figure 1 in the vicinity of the cut-off wavelength, it is clear that if the cut-off wavelength were chosen as somewhat less th~n 500 nm, the contribution of "blue-effect" light (line 11) would increase proportionately much more rapidly than the contribution of visible ligbt (line 12~ would decrease. Conversely, if the cut-off were chosen at slightly larger wave-lengths than 500 nm, the contribution of "blue-effect" light would decrease proportionately much less than the contribution o~ visible light would in-crease.
Hence, the cut-off for a curtain dye should be chosen as far to the left in Figure 1 as is consistent with yielding an acceptable stare time for the use intended.
While the perfect cut-off filter ~one in which the transmission changes from 0 to 100% completely at a given wavelength as in seement 14, Figure 1) is not physically attainable, cut-off fi]ters c~ be made whose trar,sition is sufficiently sharp, and whose transition from relatively opaque to relatively transparent takes place over a n~lrxow waveleTIgtll ~and. A
desirable example of such filters has a characteristic shown in Flgure 2 as line 20. It will be noted that the segment 22 of r~pid rise is rea~onably near to vertical, and that the cut-off' "foot~ 100 reduces the ~'blue-effect"
better than any of the "prior art't curtains whose spectra are shown in T~'igure 2, and in which the "foot" is not minimized.
A most desirsble dye would have its most nearly vertical segment corresponding to segment 14 in Figure 1 displaced f'rom 491 nm, and wol~d have as sharp a cut-off as possible on the shorter wavelength side, màrked 103 in Figure 1. The sharp cut-off at the foot is far more important than a sharp cut-off at the high transmission end of the transition, marked 102, since for a real curtain dye the unavoidable slope of the segment correspond-ing to segment 14 in Figure 1, or segment 22 in Figure 2 has carried the long wavelength shoulder far to the right of the wavelength 491 nm. The additional contribution to hazard from blue light (B, Figure 1, line 11) at the top cut-off wavelength is very small; the change in luminous ef'~ect depending on V
(Figure 1, line 12) is proportionally not great.
The consequence o~ this analysis is that the most use~ul d~es for the curtains under consideration must have a steep rise (compare segment 14 in ~igure 1), a sharp foot (compare foot 100 in Figure 2), and the steep rise should take place at a wavelength removed from 491 nm. The last part of' the requirement comes about since the sensitivity o~ the ratio ~VLT/~BLT is greatest at 491 nm, relatively slight changes in the concentration of the dye in the curtain, and hence in the transmissivity, will shi~t the value ~VLT/~BLT unacceptably due to unavoidable manufac-turing process variations.
- 19 ~
"L" represents the spectral radiance of the source.
A description of a dye for optimum curtain manufacture i8 best done by specifying design points in the curve of Figure 2.
The transmission vs wavelength curve (~igures 1 and 2) should have limits as follows:
Limit 23: at 450 nm, the relative transmission should not be greater than 0.01 (1%).
Limit 24: at 491 nm~ the relative transmission should not be greater than 0.05 (5%).
Limit 24a: at 600 nm, the relative transmission should be at least (70~).
This relates only to an organic plastic matrix with dye, with smooth surfaces, and without any scattering function. These additional functions will improve the curtain even without the optimum dyes. Figures 1 and 2 illustrate only the dye's function.
Control and variation of permissible stare time i5 accompli~hed by means of the following procedures.
I. SPECTR L_ PACE DISCRIMINATION
The dye composition and concentration is varied so that the segment corresponding to line 14 in Figure 1 is displaced sensibly parallel to it-self, but to the right or left.
II. SPATIAL FREQUENCY DISTRIBUTION
Surface refraction is used to preferentially reduce the brightness of the image of the small arc spot on the retina, and therefore decrease the sum ~BLT on the retina, while leaving the intensity of large features of the scene sensibly unchanged.
III. FEATURES OF SCBNE CONTRAST EQUALIZATION
Surface and volume scattering reduce the value of LLT and ~LT~ and h cause th~ curtain to scatter light to the general field of view. l'his causes the iris to contract and diminishes the ~ize of the pupil of the eye, and BO
the energy delivered to the retina at the lmage location of the arc æpot :Ls further diminished.
IV. FEA~URES OF_FLUORESCE~T ~IAVELENGTH SHIFTING
This will add to the illumination of the ~cene, further reducine the size of the pupil, hence the energy aelivered to the retina at the image location of the arc spot is further diminished. On the other hand, the value of VL~ will be increased because some of the fluorescent light falls on the scene and increases the ~eneral visible-light level by which features of the scene are seen. This last factor can offset some or all of the loss of ~VLT
caused by scatterine discussed in III directly above, but it does not change the effect of III in diminishing ~BLT.
In Table I there is shown a list of materials of construction with which it is possible to make the best known mode of curtain, and also to make curtains of lesser but still adequate performance, and to make some advan-tages of the invention available even in curtains having dyes which do not function according to the criteria of this invention.
In describing the dyes, considerable difficulty is encountered, because their compositions tend to be regarded by their manufacturers as trade æecrets. In general, metallic azo dyes, a well-known type of dye, are preferred for their stability. Curtains with such dyes should last a con-siderable time without undue fading, because metallic azo dyes are quite resistant to fading. However, any type of dye with a suit&ble cut-off in accordance with meeting the criteria of this invention, can be used instead of the exemplar~- dyes disclosed herein.
As to the scattering materials, their size is selected to approx-imate the wavelength preferentially to be scattered. ~he most appropriate - 21 ~
materials are any o~ the following: air bubbles, zinc oxide powder, ~luo-rescent zinc oxide powder, titanium dioxide powder, or mixtures of them~
Fluorescent zinc oxide performs a dual function of both scattering and fluorescing.
The fire retardant is selected in addition to ita ~a~or Pun~tion, for having an optic~l lndex of' refraction nearly equal to -k'hat Or -the base polymer. Then the mixture is as transparent as the ma-trix.
The organic plastic matrix is preferably polyvinylc'hloride. It works well, is well-understood, and has a suitable life. Of course other transparent organic plastic materials could be used instead. Pol~vinyl-chloride is given merely as an example of a large number of sui-table mate-rials.
The plasticizers will be those known in the art for use with the selected matrix material.
Ultraviolet absorbers are well-kno~n, and need no detailed descrip-tion here.
BEST MODE CURTAIN (with reference to Table I). Percentages are by weight and are approximate~
The identified "Base Polymer": 41%
DOP plasticizer : 41%
The metallic azo dye identified as Sc-39-3 s/s bright orange : 1-1/3%
The fluorescent orange dye identified as C507XX Product No. 40-26-2 : 1/2%
The identified fluorescent zinc oxide phosphor, particle size about 500 nm : 0.17%
The identified W absorber : 1%
Theidentified fire reterdant : 15%
This curtain will be provided with declivities on both of its surfaces, produced by reticulation.
OTHER CU~TAINS:
1. The "2nd choice" f`luorescent orange dye may be subs-tituted for ~he fluorescent dye in the best mode cur-tain.
2. The "2nd choice" pigment (titanium dioxide), zinc ox-lde~ or air bubbles of the same size, may be substituted ~`or the iluorescent zinc oxiae.
3. Dioctyl azelate may be substituted -for the DOP plasticizer.
4. The "2nd choice" metallic azo dye may be substituted ~or t,be first choice dye.
5. The curtains ~ith different dyes, the scattering materials, or sur-face treatment, or both9 can be provided.
TABLE I
MATERIALS OF CONSTRUCTION
AMOUNT
PURPOSE OF USED IN ~UFAClURERS
COMPOMENT MATERI~L OENERAL MANUFACI'URERS CURTAIN NAME AND
IN CURTAIN NAME PART NUMBER % WT. LOCATION _ _ Base Polymer Poly Vinyl PVC 75 to 35% Conoco Chemicals Chloride POLYMER typically Di~. o~ Con-(PVC) 41% tinental Oil Co.
Houston, Texas Plasticizer Dioctyl DOP 25 to 50% Mobay Chemical Phthalate Plasticizer typically Corp.
(D.O.P.) 1~1% Pittsburg9 Pa.
~Di-2-Ethyl-hexyl phtha-late]
Orange Dye with Metallic Sc-39-3 s/s 1/2 to 7-K Color Corp.
cut-off at 540 nm Azo Bright Orange 1-1/2% Hollywood, Ca.
and high light typically stability 1-1/3%
- 23 ~
TABLE I CONT'D
MATERIALS OE CONSTRUCTION
A~IOUN~' PURPOSE OF USED IN MANUFAC~RE~S
COMPONENT MATERIAI, GENERAL MANUFACTURERS CURTAIM NAME A~D
IN CURTAIN NAME P~Rl' NUMBER % WT. LOCATIOII
Fluorescent Hetero- C507XX 1/4 to 1% Shannon Luminous orange dye with cyclic oil Product No. typlcally Materials Inc.
cut-o~f at 540 soluble 40-26-2 1/2% Hollywood, Ca.
nm stimulated by mobile 300 nm to 400 nm emits at 420 nm to 600 nm with peak at 550 nm Light scattering Fluores- Ottalume 0.05 to Ottawa Chemical Fluorescent Pigment cent 2100 M 0.5% Div. of Ferro 0.5 to 2 micron Zinc Oxide typically Corporation Dia. stimulated by Phosphor 0.17% Toledo, Ohio.
250 nm to 400 nm emits at 500 nm W Absorber 2-Hydroxy- W-Chek 1/2 to 1% Ferro Ottawa 4-N- AM300 typically Corp.
Octoxy- 1% Toledo, Ohio.
benzo-phenone Fire Retardant Bariu~ MetaBusan ll-Ml 10 to 20% Buckman Labora-Index of Refraction Borate typically tories Inc.
1.5 Pigment 15% Memphis, Tenn.
Orange ~ye with cut- Metallic Pylam Orange 1/2 to Pylam Products off at 540 nm, and Azo 727782 1 1/2% Company, Inc.
high light stability typically Queens Village, (2nd choice) 1-1/3% New York 926-4461 Ingham Fluorescent Orange Alcohol C507 x 1/4 to 1% Shannon Lu~inous Dye with cut-o~f at Soluble typically Materials Inc.
540 nm, stimulated 40-25-3 1/2% Hollywood, Ca.
by 300 nm to 400 nm and emits at 420 nm to 600 nm with peak at 550 nm (2nd choice) rrABLE I CONrr'D
. .
MATERIALS OF CONSTRUCrrION
.. .. . . _ _ AMOU:~r~
PURPOSE OF U~ED IN MANUFACTU~S
COMPOMENrr MAl~RIAL GENERAL MANUFACrrURERS CUR~AIN NAME AND
IN CURTAIN rlAME PARrr NUMBER % ~rr~ LOCArTION
Light Scattering rritanium RF-3 0.05 to New Jersey Zlnc Pigment Dioxide O~5% Company 0.5 to 2 Micron typically Bethlehem, Dia (2nd choice) 0.17% Pennsylvania Plasticizer Dioctyl Plastolein 25-50% Emery Industries (2nd choice) Azelate 9058 typically Cincinn~ti, Ohio (DOZ) DOZ 4l%
TABLE I
MATERIALS OF CONSTRUCTION
AMOUNT
PURPOSE OF USED IN ~UFAClURERS
COMPOMENT MATERI~L OENERAL MANUFACI'URERS CURTAIN NAME AND
IN CURTAIN NAME PART NUMBER % WT. LOCATION _ _ Base Polymer Poly Vinyl PVC 75 to 35% Conoco Chemicals Chloride POLYMER typically Di~. o~ Con-(PVC) 41% tinental Oil Co.
Houston, Texas Plasticizer Dioctyl DOP 25 to 50% Mobay Chemical Phthalate Plasticizer typically Corp.
(D.O.P.) 1~1% Pittsburg9 Pa.
~Di-2-Ethyl-hexyl phtha-late]
Orange Dye with Metallic Sc-39-3 s/s 1/2 to 7-K Color Corp.
cut-off at 540 nm Azo Bright Orange 1-1/2% Hollywood, Ca.
and high light typically stability 1-1/3%
- 23 ~
TABLE I CONT'D
MATERIALS OE CONSTRUCTION
A~IOUN~' PURPOSE OF USED IN MANUFAC~RE~S
COMPONENT MATERIAI, GENERAL MANUFACTURERS CURTAIM NAME A~D
IN CURTAIN NAME P~Rl' NUMBER % WT. LOCATIOII
Fluorescent Hetero- C507XX 1/4 to 1% Shannon Luminous orange dye with cyclic oil Product No. typlcally Materials Inc.
cut-o~f at 540 soluble 40-26-2 1/2% Hollywood, Ca.
nm stimulated by mobile 300 nm to 400 nm emits at 420 nm to 600 nm with peak at 550 nm Light scattering Fluores- Ottalume 0.05 to Ottawa Chemical Fluorescent Pigment cent 2100 M 0.5% Div. of Ferro 0.5 to 2 micron Zinc Oxide typically Corporation Dia. stimulated by Phosphor 0.17% Toledo, Ohio.
250 nm to 400 nm emits at 500 nm W Absorber 2-Hydroxy- W-Chek 1/2 to 1% Ferro Ottawa 4-N- AM300 typically Corp.
Octoxy- 1% Toledo, Ohio.
benzo-phenone Fire Retardant Bariu~ MetaBusan ll-Ml 10 to 20% Buckman Labora-Index of Refraction Borate typically tories Inc.
1.5 Pigment 15% Memphis, Tenn.
Orange ~ye with cut- Metallic Pylam Orange 1/2 to Pylam Products off at 540 nm, and Azo 727782 1 1/2% Company, Inc.
high light stability typically Queens Village, (2nd choice) 1-1/3% New York 926-4461 Ingham Fluorescent Orange Alcohol C507 x 1/4 to 1% Shannon Lu~inous Dye with cut-o~f at Soluble typically Materials Inc.
540 nm, stimulated 40-25-3 1/2% Hollywood, Ca.
by 300 nm to 400 nm and emits at 420 nm to 600 nm with peak at 550 nm (2nd choice) rrABLE I CONrr'D
. .
MATERIALS OF CONSTRUCrrION
.. .. . . _ _ AMOU:~r~
PURPOSE OF U~ED IN MANUFACTU~S
COMPOMENrr MAl~RIAL GENERAL MANUFACrrURERS CUR~AIN NAME AND
IN CURTAIN rlAME PARrr NUMBER % ~rr~ LOCArTION
Light Scattering rritanium RF-3 0.05 to New Jersey Zlnc Pigment Dioxide O~5% Company 0.5 to 2 Micron typically Bethlehem, Dia (2nd choice) 0.17% Pennsylvania Plasticizer Dioctyl Plastolein 25-50% Emery Industries (2nd choice) Azelate 9058 typically Cincinn~ti, Ohio (DOZ) DOZ 4l%
Claims (29)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A curtain for protecting an observer from damage by light from welding arcs, said curtain being sufficiently transparent to see through it an object of substantial size, said curtain comprising:
an organic plastic matrix material which itself is inherently transparent and which is formed into a sheet with a pair of surfaces and a dimension of thickness between said surfaces; and dye distributed throughout said matrix material, said dye being provided in concentrations which permit the sheet to transmit at least 70% of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmission of said sheet with dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm.
an organic plastic matrix material which itself is inherently transparent and which is formed into a sheet with a pair of surfaces and a dimension of thickness between said surfaces; and dye distributed throughout said matrix material, said dye being provided in concentrations which permit the sheet to transmit at least 70% of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmission of said sheet with dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm.
2. A curtain according to claim 1 in which said dye is selected from the group consisting of fluorescent dyes which radiate substantial light in wavelengths between about 450 nm and 700 nm, metallic azo dyes, and combina-tions thereof.
3. A curtain according to claim 1 in which discontinuities are dis-tributed throughout the matrix material, said discontinuities having an optical index of refraction which differs from the optical index of refraction of the matrix material by at least 0.2 units, whereby to scatter at least 5%
and less than 50% of the light which passes through the sheet.
and less than 50% of the light which passes through the sheet.
4. A curtain according to claim 1 in which one of said surfaces is formed with a plurality of declivities having faces disposed at angles to the plane of the sheet, whereby some rays of light which passes through said one surface are refracted and undergo a change in direction.
5, A curtain according to claim 3 in which one of said surfaces is formed with a plurality of declivities having faces disposed at angles to the plane of the sheet, whereby some rays of light which passes through said one surface are refracted and undergo a change in direction.
6. A curtain according to claim 2 in which discontinuities are distri-buted throughout the matrix material, said discontinuities having an optical index of refraction which differs from the optical index of refraction of the matrix material by at least 0.2 units, whereby to scatter at least 5% and less than 50% of the light which passes through the sheet.
7. A curtain of substantial area for forming at least a portion of the perimeter of an area in which an electrical arc welding or an electrical arc cutting operation is conducted, for the purpose of protecting the eyes of an observer located outside of said perimeter from damage by light from said arcs, said curtain comprising:
an organic plastic matrix material which itself is inherently transpar-ent and which is formed into a sheet with a pair of surfaces and a dimension of thickness between said surfaces;
an ultraviolet absorber distributed throughout said matrix material; and dye distributed throughout said matrix material, said dye, being of the class, and being present in concentrations, which permit the sheet to transmit at least 70% of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmissions of said sheet with dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm, said curtain being sufficiently clear for said observer to see through it an object of substantial size located inside said perimeter.
an organic plastic matrix material which itself is inherently transpar-ent and which is formed into a sheet with a pair of surfaces and a dimension of thickness between said surfaces;
an ultraviolet absorber distributed throughout said matrix material; and dye distributed throughout said matrix material, said dye, being of the class, and being present in concentrations, which permit the sheet to transmit at least 70% of the radiation incident upon it which has wavelengths between about 600 nm and about 1,400 nm, the relative transmissions of said sheet with dye being no greater than 0.01 at 450 nm, no greater than 0.05 at 491 nm, and at least 0.70 at 600 nm, said curtain being sufficiently clear for said observer to see through it an object of substantial size located inside said perimeter.
8. A curtain according to claim 1 or 7 in which the said curtain additionally includes a fire retardant.
9. A combination according to claim 7 in which said dye is selected from a group consisting of flourescent dyes which radiate substantial light in wavelengths between about 450 nm and 700 nm, metallic azo dyes, and combinations thereof.
10. A combination according to claim 1 or 7 in which said dye is metallic azo dye.
11. A combination according to claim 1 or 7 in which said dye is a fluorescent dye that radiates substantial light in wavelengths between about 450 nm and about 700 nm and is migratory in said matrix material.
12. A combination according to claim 7 in which discontinuities are distributed throughout the matrix material, said discontinuities having an optical index of refraction which differs from the optical index of refrac-tion of the matrix material by at least 0.2 units, and being present in such condition and quantities as to scatter at least 5% and less than 50% of the light which passes through the sheet whereby to cause a decrease in scene contrast.
13. A combination according to claim 3, 6 or 12 in which said discon-tinuities are of a size approximating 500 nm, whereby preferentially to scatter radiation of this wavelength.
14. A combination according to claim 3, 6 or 12 in which said discon-tinuities are selected from the group consisting of air bubbles, zinc oxide powder, fluorescent zinc oxide powder, titanium-dioxide powder, and mixtures thereof.
15. A combination according to claim 3, 6 or 12 in which said discon-tinuities are zinc oxide powder.
16. A combination according to claim 3, 6 or 12 in which said discon-tinuities are fluorescent zinc oxide powder, whereby to function as an ultra-violet absorber, fluorescent light source, and scattering means.
17. A combination according to claim 3, 6 or 12 in which said discon-tinuities are titanium-dioxide powder.
18. A combination according to claim 7 in which one of said surfaces is formed with a plurality of declivities having faces disposed at angles to the plane of the sheet, whereby some rays of light which pass through said one surface are refracted and undergo a change in direction.
19. A combination according to claim 9 in which discontinuities are distributed throughout the matrix material, said discontinuities having an optical index of refraction which differs from the optical index of refraction of the matrix material by at least 0.2 units, and being present in such con-centrations and quantities as to scatter at least 5% and less than 50% of the light which passes through the sheet, whereby to cause a decrease in scene contrast.
20. A combination according to claim 19 in which said discontinuities are of a size approximating 500 nm, whereby preferentially to scatter radiation of this wavelength.
21. A combination according to claim 19 in which said fluorescent dye is migratory in said matrix material.
22. A combination according to claim 9 in which one of said surfaces is formed with a plurality of declivities having faces disposed at angles to the plane of the sheet, whereby some rays of light which pass through said one surface are refracted and undergo a change in direction.
23. A combination according to claim 4, 18 or 22 in which said ankles are less than about 8 minutes of arc.
24. A combination according to claim 4, 18 or 22 in which the declivities have non-planar surfaces.
25. A combination according to claim 4, 18 or 22 in which said declivi-ties are formed by reticulation.
26. A combination according to claim 4, 18 or 22 in which said declivi-ties are formed on both surfaces of the curtain, the said angles being less than about four minutes of arc.
27. A combination according to claim 12 in which one of said surfaces is formed with a plurality of declivities having faces disposed at angles to the plane of the sheet, whereby some rays of light which pass through said one surface are refracted and undergo a change in direction.
28. A combination according to claim 19 or 27 in which said discontinui-ties are selected from the group consisting of air bubbles, zinc oxide powder, fluorescent zinc oxide powder, titanium-dioxide powder, and mixtures thereof.
29. A combination according to claim 12 or 27 in which said dye is selected from the group consisting of fluorescent dyes which radiate substan-tial light in wavelengths between about 450 nm and 700 nm, metallic azo dyes, and combinations thereof.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000395904A CA1153593A (en) | 1978-09-27 | 1982-02-09 | Curtain for shrouding welding operations |
| CA000395903A CA1163844A (en) | 1978-09-27 | 1982-02-09 | Curtain for shrouding welding operations |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94616378A | 1978-09-27 | 1978-09-27 | |
| US946,163 | 1978-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1121192A true CA1121192A (en) | 1982-04-06 |
Family
ID=25484037
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336534A Expired CA1121192A (en) | 1978-09-27 | 1979-09-27 | Curtain for shrouding welding operations |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5547096A (en) |
| CA (1) | CA1121192A (en) |
| DE (1) | DE2938959A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4707860A (en) * | 1983-03-24 | 1987-11-24 | Holmstroem Per Olof | Welding shield |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6046356A (en) * | 1983-08-22 | 1985-03-13 | Mitsubishi Heavy Ind Ltd | Preparation of precipitation hardening type alloy member |
| JPS6384779A (en) * | 1986-09-30 | 1988-04-15 | Achilles Corp | Welding curtain material |
| US10791608B2 (en) * | 2017-01-12 | 2020-09-29 | Signify Holding B.V. | Lighting control |
-
1979
- 1979-09-26 DE DE19792938959 patent/DE2938959A1/en not_active Withdrawn
- 1979-09-27 CA CA000336534A patent/CA1121192A/en not_active Expired
- 1979-09-27 JP JP12522279A patent/JPS5547096A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4707860A (en) * | 1983-03-24 | 1987-11-24 | Holmstroem Per Olof | Welding shield |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5547096A (en) | 1980-04-02 |
| DE2938959A1 (en) | 1980-04-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |