U.S. patent number 3,784,817 [Application Number 05/142,190] was granted by the patent office on 1974-01-08 for radio luminescent sighting arrangement.
This patent grant is currently assigned to Atlantic Richfield Company. Invention is credited to Dean B. James, Seymour H. Smiley, Ralph E. Whittaker, Jr..
United States Patent |
3,784,817 |
James , et al. |
January 8, 1974 |
RADIO LUMINESCENT SIGHTING ARRANGEMENT
Abstract
An illuminating arrangement is disclosed which, in one
particular embodiment, includes a pair of optically-alignable
"sight markings", the markings being illuminated and defined, at
least in part, by a "radio-luminescent" segment, especially suited
for a dimly-lit field of view, these segments including a
phosphorescent material and a "matched" radio-isotope adapted to
induce prescribed phosphorescence.
Inventors: |
James; Dean B. (Delmont,
PA), Smiley; Seymour H. (Pittsburgh, PA), Whittaker, Jr.;
Ralph E. (Upper St. Clair, PA) |
Assignee: |
Atlantic Richfield Company
(Glenolden, PA)
|
Family
ID: |
22498914 |
Appl.
No.: |
05/142,190 |
Filed: |
May 11, 1971 |
Current U.S.
Class: |
250/467.1 |
Current CPC
Class: |
F41G
1/32 (20130101) |
Current International
Class: |
F41G
1/32 (20060101); F41G 1/00 (20060101); F21k
002/02 () |
Field of
Search: |
;250/71R,77,78 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Borchelt; Archie R.
Attorney, Agent or Firm: Eubank; John R. Martin, Jr.; John
C.
Claims
What is claimed is:
1. In a sighting arrangement including sight marking means and
supporting means, the arrangement being adapted to enable an
operator to position the supporting means so as to align the
marking means along a prescribed sighting axis, extending between a
point of origin and a target point, this arrangement including an
elongate chamber arranged along a portion of the axis wherein at
least one reference point along the axis is to be indicated by one
or more marking segments, the improvement therein comprising:
at least one illumination arrangement comprising a translucent
housing containing radio-luminescent means adapted to project an
illumination beam to delineate at least one of said marking
segments, said radio-luminescent means comprising a matrix of clear
plastic material in which are relatively homogeneously suspended
particles of a phosphorescent material emitting light in the
visible red spectrum, and particles of Promethium-147 isotope
material as an activating radio-isotope material.
2. The combination recited in claim 1 wherein said phosphorescent
material comprises a zinc sulfide type phosphor.
3. The combination as recited in claim 1 wherein the sighting
arrangement comprises a gunsight for a weapon.
4. An optical marking device for defining an "alignment pattern"
under low-illumination conditions comprising at least one
radio-luminescent capsule, this capsule comprising container means,
luminescent means comprising a matrix of clear plastic material in
which are relatively homogeneously suspended particles of
phosphorescent material and particles of Promethium-147 sealed
within said container means to provide initially a surplus amount
of luminescence emitting light rich in the visible red spectrum and
instantly regulatable shielding means for masking out a portion of
said luminescence to define said pattern, at least a portion of
said container means being sufficiently translucent to emit the
requisite luminescence to define the said pattern appropriately for
the conditions prevailing at the time of regulating the shielding,
whereby durable utility for the marking device is attainable not
merely throughout a variety of illumination conditions but also
after significant decay of the radioisotope.
Description
BACKGROUND OF THE INVENTION
When using a sighting arrangement, (such as the sights on a rifle,
pistol or other weapon) under conditions of low-level (poor)
ilumination, an operator (e.g., a rifleman) often is unable to
perceive the sight markings and is thus hampered in the use of the
device. For instance, when a rifleman is aiming his weapon in the
half-light of near-dusk or moonlight, he may be able to dimly
perceive his target but will often have difficulty identifying the
markings or critical edges of the rifle sights. The brightness of
the illumination should be just sufficient to provide adequate
definition. If it is too bright, the operator will be blinded; or,
at least, his ability to perceive the dimly-lit target will be
impaired.
Various arrangements have been considered to illuminate such
sighting devices; for instance, a (miniaturized) battery-powered
lamp has been suggested, preferably in combination with
light-conducting fibers (light-pipes) so as to remotely-locate the
lamp and completely shield it, the fibers conducting the light from
the lamp to illuminate the eyepiece markings. Such arrangements may
use a miniaturized lamp-battery combination, together with a small
variable resistance for adjusting the current to the lamp, and
resultant brightness e.g., permitting a rifleman to illuminate his
sights sufficiently to aim his weapon but not so bright as to
interfere with his vision, nor to generate glare about the sight
markings, or, especially, not such as to signal his presence to the
enemy. The minimal brightness that is required will vary with the
darkness of the surroundings. This battery-powered, lamp-fiber
arrangement has not proved very satisfactory, partly because the
batteries and lamps involved are not sufficiently reliable. This is
particularly so for military field applications, where extremes of
temperature, moisture, shock and vibration etc. are encountered;
e.g., in the use of an Army rifle in jungle warfare. Such an
arrangement is also undesirably bulky and inconvenient to mount on
the typical weapon. The use of a single spot of radio-luminescent
material at the center of a circular, transparent reticle has been
considered as a means of illuminating the rear sight of a rifle.
This appears to present some difficulties, partly because a halo of
light floods the reticle, obstructing vision and also because the
radio-luminescent spot is white in color; furthermore, without
illumination of the foreward sight, it is difficult to properly
align the weapon.
SUMMARY OF THE INVENTION
The present invention contemplates using "radio-luminescent"
segments, preferably comprising red phosphors, to mark and define
(at least a portion of) the sight markings (or critical edges) in
such sighting devices. These radio-luminescent markings will
provide adequate and variable (red) illumination of the sight
markings, without interfering with the convenient use of the
weapon. By using a red phosphor, the illumination can be brighter,
providing better definition to the markings or critical edges,
without blinding the operator or being visible to the target.
It will be evident that a primary object of the subject invention
is to solve at least some of the foregoing problems and provide at
least some of the foregoing features and advantages. A related
object is to provide optical sighting devices with
"radio-luminescent" segments defining at least a portion of the
sight markings.
A further object is to provide such radio-luminescent segments
using particular isotopic materials which are sufficiently active
to provide for adequate stimulation of the phosphorescent material,
but which emit a minimal amount of penetrating radiation that does
not constitute a health hazard to the operator.
A related object is to provide such radio-luminescent segments
using particular phosphorescent materials such as zinc sulfides,
yttrium (europium) vanadates, gadolinium(europium) oxides, or like
red phosphors in order to provide maximum illumination of the sight
markings or critical edges without impairing the vision of the
operator or permitting the weapon to be located by the intended
prey.
A further related object is to use such red phosphor materials in
combination with Promethium-147 (isotope) so as to properly
activate the phosphor and provide prescribed illumination with a
minimum of penetrating, exterior, ionizing radiation and with an
adequate brightness half-life associated with the illumination to
provide for satisfactory operation over a period of several
years.
Other objects are to miniaturize sight-illuminating arrangements,
to eliminate problems associated with portable battery lamps, light
fibers, and other devices, and to optimize the use of
radio-luminescent materials so that the aforedescribed problems are
avoided.
How the foregoing and other more specific objects are achieved will
appear and become evident through consideration of the ensuing
description of preferred embodiments of the invention in
conjunction with the associated drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a highly schematic isometric view of an embodiment of the
invention, with parts omitted or indicated only functionally for
clarity.
FIG. 2 is a schematic isometric view of a "rear sight" embodiment
like that in FIG. 1 but modified somewhat.
FIG. 3 is a schematic isometric view of a "front sight" embodiment
like that in FIG. 1 but modified somewhat.
FIG. 4 is a rather simplified isometric view of a single
"radio-luminescent marking segment" modified and indicated as
rotatable about its own axis to make the emanating illumination
variable in quality and/or intensity.
FIG. 5 is an upper perspective view of a radioluminescent tube
embodiment suitable for use in the arrangements of FIGS. 1 to
4.
FIG. 6 is a very schematic isometric view of other embodiments
illustrating means for selectively varying illumination quality and
intensity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a suitable application environment for a
preferred embodiment of the invention to be described. Here, an
optical sighting arrangement OSA is shown, comprising front and
rear sights, 30 and 20, respectively, that are shown mounted,
through associated brackets 35 and 25, respectively, upon a common
support -- indicated in phantom as support B which, for purposes of
illustration, may be understood as including the frame portion of a
rifle or like weapon supporting the optical sighting device, being
used by an operator for aiming the weapon in a manner understood in
the art. Accordingly, sights 20 and 30 (being functionally shown)
may be understood as aligned along a common optical (sighting) axis
SA, shown in phantom extending from the working end or origin O
(operator's eye) of the sighting device along, and through, the
sighting arrangement to terminate at a selected target locus T. The
sighting arrangement is adapted, conventionally, to enable an
operator to aim the piece so as to hit a prescribed target zone
(here indicated as the center of target T). Axis SA thus defines
the center of the field of view associated with the sighting
arrangement, terminating at the center of illustrative target
T.
Front sight 30 comprises a cylindrical "radio-luminescent tube" 33
mounted in alignment with, and concentric along, axis SA upon a
suitable arm 31 which, in turn is attached to fixed bracket 35.
Rear sight 20 comprises a planar opaque supporting plate 21 of any
suitable shape and dimension as dictated by established sight
design and accommodated upon the supporting weapon. Plate 21
includes a relieved "sighting-aperture" portion 22. Aperture 22
preferably comprises a generally circular cut-out of a radius which
defines a prescribed field of view that will surround the target
(taking into account the relative location of origin O and other
dimensions as is conventional in the art). The center 20-C of
aperture 22, lies along axis SA and forms the focus or origin from
which the upper edges of plate 21 and the pair of elongate
radio-luminescent tubes 23 and 24, mounted therealong, all extend.
Preferably, these upper "sighting-edges" ("critical edges") are
bevelled along a pair of symmetrical axes originating at focus
20-C. Sight 20 is rigidly affixed on bracket 25 which, in turn, is
affixed upon support B. Brackets 25, 35 may of course (either or
both) be adjustably affixed to support B so as to permit the
repositioning and adjusted alignment of the associated sights, as
is well known in the art. Moreover, the general mechanical
arrangements of the foregoing sighting device (including the
general configuration of sight 20) are generally known in the
art.
Radio-luminescent tubes 23, 24, and 33 may be understood as, all,
generally fashioned in the manner indicated in FIG. 5 as tube 1 and
are hereinafter described in some detail, although modified
embodiments will also serve. Radio-luminescent tube 1 comprises an
outer casing 3 enclosing and housing an inner slug 5 of
radio-luminescent material. Tube 3 preferably comprises a closed
cylinder. Radio-luminescent tube 1 can also be constructed by
suspending the fine-powder mixture of radio-luminescent material in
a monomer (or un-solidified form of any transparent plastic
material) and then fixing the radio-luminescent material within the
solidified transparent plastic material by casting it in the
desired cylindrical shape. This cylindrical shape may also be
achieved by extruding a rod of plastic material, containing the
suspended radio-luminescent material, as the plastic solidifies.
Then single tubes would be sectioned from the extruded rod. It may
be desirable to coat the impregnated "tubes" with a thin layer of
plastic material that does not contain radio-luminescent material
in order to provide a surface from which radioactive powder cannot
be released by abrasion or wear.
In the case of embodiments 23, 24, the tube is partially shielded
with an opaque material so as to provide one or more translucent
"window" sections along at least a portion of the side walls so as
to generate line-segments of illumination along the tube length at
selected circumferential locations thereof. Such a "line" of
illumination can also be achieved as in the case of tubes 23 and 24
by embedding all but a portion of the side of the tube into the
sight frame. Tube 3 is about one-quarter to one-half inches long,
as required, providing the necessary length of linear definition,
with an inner diameter of one-sixteenth to one-thirty-second inches
and with a wall thickness as may be required to provide adequate
strength and integrity to the tube.
In the case of "end-illuminated" embodiment 33, the tube is as
afore-described except, of course, that one end (only) is
translucent while the other end and the sides are opaque to shield
it optically directing illumination only back along axis SA toward
origin O. In the case of 33, the entire tube 1 can be embedded in a
metal holder, etc., exposing only the tube end to provide an
illuminated "dot" along sighting axis SA. Also, in the case of tube
33, the tube could be embedded vertically in a vertical "post-type"
sight (replacing 30), exposing only the curved end of the tube 1 to
provide an illuminated "shaft" along sighting axis SA.
The radio-luminescent materials comprising slug 5 may take a number
of forms, all receiving an energizing isotope plus a luminescent
material responsive thereto. We prefer to use phosphors of the zinc
sulfide type, that emit illumination in the red region of the
visible spectrum. We have found this particularly suitable for
night, or other low-illumination, situations, the red illumination
being less blinding to a "darkness-adapted" eye than other regions
of the visible spectrum or white light of the same brightness.
Other phosphors such as those based upon rare-earth compounds, such
as yttrium(europium) vandate, yttrium(europium) oxysulfide, or
gadolinium (europium) oxide may be used in certain situations
instead of, or in combination with, the zinc sulfide type.
Various radio-isotopes may be used as the activating energy source.
Generally, the penetrating nature of gamma radiation and its
associated health-physics problems make gamma emitting isotopes
unacceptable. Alpha-emitting isotopes may be used, but the
energy-conversion efficiency can be quite low due to short
mean-free path. Beta emitting isotopes are generally preferred. We
have considered tritium, promethium (Pm-147), krypton (Kr-85), and
strontium (Sr-90) primarily. Kr-85 and Sr-90, however, have the
disadvantage of emitting considerable penetrating gamma radiation
in addition to their beta activity, and thus present a health
hazard. The beta energy of tritium is only 1/10 that of Pm-147 and
accordingly much more must be used to provide sufficient energy to
yield a given level of brightness. For instance, tritium gas
encapsulated in a phosphor-coated glass tube can provide a
practical radio- luminescent light source for illuminated signs or
dial markings, but it is difficult to contain sufficient gas in a
tube small enough yet sufficiently intense for sight illumination.
A smaller and brighter tritium source may be attained using a
mixture of phosphor of the ZnS type and partially tritided
zirconium, yttrium, rare-earth, or similar metal powder sealed in
glass. In addition, one might conventionally combine such a tritium
source with focusing optics such as a small prism focusing the
illumination spot on a reticle (sight-marking). However, the
greenish-yellow illumination produced is not the most desirable.
Also, with such "optical coupling " the illumination-spot is apt to
be too bright and, moreover, create a "halo" effect about the
sighting mark which can interfere with the operator's perception of
a dimly-lit target. Accordingly, such "single- point source" sights
have their drawbacks.
A preferred radio-isotope is promethium-147 (Pm-147). In one form
an aqueous solution of a Pm salt may be sorbed within ceramic
microspheres, such as the synthetic zeolites, and the rinsed,
loaded spheres then fired to fix Pm.sub.2 O.sub.3 inside, with
surface activity thereafter being removed with an acid leach. Of
course, in using Pm-147 it should be borne in mind that light
intensity will decay to 1/4 approximately of the initial brightness
in about five years since Pm-147 has a 2.7 year half-life.
Accordingly, with our preferred embodiment, indicated above, Pm-147
is to be used, combined with a red-phosphorescent material.
Preferably, a zinc-sulfide phosphor and the Pm-147 microspheres are
mixed together, the sizes of both particles typically ranging from
10 to 50 microns.
Using the foregoing mixture of promethium-impregnated ceramic
microspheres and zinc sulfide phosphor particles we have found the
following relation between Pm-147 concentration and resultant
brightness, as measured in microlamberts to be illustrative of what
may be expected:
TABLE I ______________________________________ Pm-147
Concentration* Brightness** (mCi) (UL)
______________________________________ 75 120*** 25 500 8 175 4 90
2 65 ______________________________________ * milli-curies of
Promethium 147 ** brightness in microlamberts as compared to a
white, certified standard phosphorescent light source ***
brightness of a red zinc sulfide phosphorescent system in an
1/8-inch glass tube, 1/4-inch long; all other values are for white
zinc sulfide systems as circular flat spots, 3/32-inch in
diameter.
Of course, brightness can be varied from a few microlamberts (about
the intensity of a watch dial) up to a few millilamberts for the
white system (the intensity of the typical television receiver's
cathode ray tube is on the order of several hundred millilamberts;
similarly for typical military instrument dials, pushbuttons,
etc.). We prefer to keep the brightness of the red system to the
order of 100-250 microlamberts, as measured with a photometer that
has been calibrated with a similar tube of known brightness
containing Pm-147 microspheres and a white phosphor.
As a modification of the foregoing radio-luminescent composition, a
red rare-earth phosphor may be impregnated in the microspheres
along with the Pm-147 to achieve a higher conversion efficiency. In
most cases, the Pm-147/red-phosphor mixture embedded in tiny
transparent tubes which are, in turn, affixed as "marking segments"
on the sight will be the preferred embodiment because of their
desirable performance in low-illumination situations. For certain
instances, one can prepare an isotope-phosphor mixture of the type
described in conjunction with a "paint vehicle" and simply spread
it as a painted marking on the surface or critical edge of the
sight. However, this will obviously expose the radio-luminescent
mixture to risks of weathering and associated deterioration,
accidental abrasion and removal, etc. Thus, the encapsulation of
the mixture sealed within a tiny transparent glass (or plastic,
etc.) tube or suspended in a solid transparent plastic "tube" of
the type described, exposing only the end or side of the tube to
describe the desired configuration segment (i.e., the illuminated
dot or line) avoids this problem.
The dimensions of the tube 1 (length, inside and outside diameters,
etc.) may, of course, be adjusted as required by the specific
configuration of the sight to be illuminated. In general, the
front-sight will be adapted to provide a "spot source" mark (or
glowing dot) by exposing only the end of a single radio-luminescent
tube. The rear-sight will typically require one or more linear
radio-luminescent segments (light sources; e.g., provided in the
embodiment by exposing the side of tube 1) arranged to form a
"Vee", a "U", a square, or similar geometries, within which the
"front spot" is to be positioned (aligned with) during a typical
sighting routine.
FIGS. 2 and 3 illustrate rear and front rifle sights, 20', 30'
respectively along the lines of the embodiment in FIG. 1 but
slightly modified and, of course, shown in somewhat greater detail
and in enlarged scale. Thus, rear sight 20' is generally the same
as sight 20 in FIG. 1 (except where indicated) and includes a
cut-out (aperture) 22' in an opaque plate 21' with a pair of
opposed, similar radio-luminescent-tube-receiving slots 24-S, 23-S
flanking aperture 22', each slot being aligned along (parallel to)
the upper edges of sight 20', these edges being bevelled to
comprise a "V" configuration, the arms of which originate from
associated optical axis SA (as in the embodiment of FIG. 1). Plate
21' may assume any convenient dimensions (e.g., on the order of a
few eighths of an inch square by a few sixteenths in thickness,
with the radius of slots 24-S, 23-S and cut-out 22' being a few
sixty-fourths).
Front sight 30' is also generally the same as sight 30 in the
embodiment of FIG. 1 except where specified, and includes a holder
31' (our mounting device) including a hole 33-S for receiving the
associated radio-luminescent-tube. Mount 31' will be assumed as
formed of metal, opaque plastic or the like and adapted to mask out
any stray light from the glowing radio-luminescent tube in hole
33-S, except for the light-spot projected back along optical axis
SA toward rear- sight 20' (as with the embodiment of FIG. 1).
Holder 31' will be suitably dimensioned (e.g., cross-sectional
dimensions of several thirty-seconds inch with a radius being
cut-out across its base to provide for its being mounted on the
barrel of the weapon.
INTENSITY ADJUST
According to a further improvement and feature of novelty, the
radio-luminescent tubes may be made adjustable in brightness
(intensity of illumination). For example, this allows an operator
to adjust brightness of the illuminated segment markings of his
sighting device to suit the lighting conditions of his environment
and relative to the brightness of the target T within his field of
view at a particular time. If the environment surrounding the
operator is brighter (but still insufficient to permit him to
define his sights without the aid of illumination), the sight
illumination must be brighter to provide adequate definition. If,
however, the environment is quite dark, (but still sufficient to
illuminate the target), it may be necessary to reduce the sight
illumination from that required for the brighter environment to a
lower level of sight illumination that will not interfere with the
ability of the operator to perceive him dimly-lit target.
Thus, a radio-luminescent tube 1' (analogous to tubes 23, 24, etc.)
as indicated in FIG. 4 may be enclosed (to intercept useful
illumination) by rotatable filter CF adapted to provide selectable
levels of emanating brightness on the linear sight markings. Filter
CF is adapted to be rotated relative to tube 1' selectably
interposing optical filters of varied opacity between the
radio-luminescent phosphor source and the illuminated marking
across the given field of view (angular field Fo V indicated). A
radio-luminescent tube 1' may be understood as constructed
generally along the lines of tube 1 in FIG. 5, comprising
radio-luminescent slug 5' surrounded by transparent encapsulation
tube 3' (or as comprising radio-luminescent material suspended in
transparent solid plastic), which in turn is surrounded by filter
CF (at least across field Fo V). Filter CF is provided with various
strip portions or segments S1, S2, S3, etc. of selected, different
opacities as known in the art and is made rotatable with respect to
the enclosed radio-luminescent tube. Thus, for instance, when a
given angular sector of the tube is exposed across the field FoV
(e.g. as defined by the mask provided by plate 21' in FIGS. 2A, 2B)
then a prescribed, selected light-attenuating strip S-3 of
prescribed opacity will be interposed to set the level of
illumination as selected by the operator. For a different
illumination, the filter CF may be shifted (by mechanical means
known in the art but not shown) to interpose another filter strip
of different corresponding opacity. The adjustable linear
illumination may also be provided by coating the tube with segments
of a transparent material of varying opacity in each segment and
then providing for the entire coated tube to be rotated, exposing
the each segment to the unshielded portion of the mounting.
The means for mounting the luminescent tube and its surrounding
filter so as to be rotatable with respect thereto in a given
gunsight configuration will be apparent to those skilled in the art
and will not be dwelt upon here. Filter CF may, for instance,
comprise an arcuate segment of film spanning the length of the
luminescent tube, with the strips of varying opacity each being
long enough to cover the exposed "window" (field Fo V) involved in
the subject mounting arrangement.
A further modification for varying the emanating intensity is shown
(very functionally) in FIG. 6 where an exemplary radio-luminescent
tube 10 (understood as along the lines of those described before
and adapted to emit light of a given original intensity from its
exposed head portion -- not shown but generally indicated as light
rays P focused at marking spot (CH). Tube 10 is adapted to project
radiant energy at a given original intensity to be focused (by
optics not shown, but well understood in the art) onto a prescribed
spot CH portion of a sighting screen or reticle F. Spot CH will,
for instance be the functional analog of the spot of light
projected by the end of tube 33 in the embodiment of FIG. 1 and
adapted to define the center of the sighting axis SA in the given
sighting arrangement. Also shown is an intensity adjusting filter
means F comprising a generally-circular disc having (quadrant)
sections FS-1, FS-2, etc. of different selectable opacities, filter
F being rotatable as indicated (e.g., by the operator) to interpose
one of the sections FS between radio-luminescent source 10 and the
operator's eye and thereby allow a selectable adjustment of the
intensity of the light projected as spot CH. One may use a like
arrangement employing a filter belt. Thus, it will be apparent that
where the embodiment involves a sighting spot CH on the gunsight of
a rifle used in low illumination situations (night fighting) for a
target T the rifleman/operator may rotate filter F to provide a
sighting spot CH of an intensity selected to most closely suit the
level of target illumination at a particular time. Obviously,
filter F may include virtually any number of selectable filter
sections having different opacities and/or filtering
characteristics (e.g., color) and may take the form of other
analogous devices for selectably attenuating the level of
illumination projected from the radio-luminescent source.
Those skilled in the involved art will readily understand that the
subject invention may take other analogous forms still falling
within the spirit and scope of the subject invention as defined by
the appended claims for instance, involving variations in
structure, materials, or processes used. For instance,
radio-luminescent devices of the type described may obviously be
used in defining the markings of other sighting or like
arrangements while in certain cases, other phosphors and/or other
radio-isotope materials may in certain instances be apt for
achieving the indicated results and performing at least some of the
described unique functions.
* * * * *