Note: Descriptions are shown in the official language in which they were submitted.
968Z
This is a divisio~l of application ~erial No. 291,686
filed November 24, 1977.
This invention relates to lighting apparatus, and
more particularly to a surgical luminaire having improved
focussing, light-shielding, and cooling properties.
The stringent requirements for proper and adequate
lighting in the modern-day operating room have resulted in a
continuing effort to improve the lighting apparatus used in
such environments. Prior efforts generally have followed the
approach of providing bigger lighting fixtures and increased
light intensities, with the result that many such lighting
devices on the market today are extremely large, heavy de-
vices. Further, the high-intensity light source or sources
used in such devices generate excessive heat and produce sub-
stantial glare, and generally are not completely shielded from
direct or indirect view from outside so that operating room
personnel may have to consciously avoid looking at the lights
to thereby avoid temporary sight impairment during surgery.
Inability to adequately focus the light from these prior
art devices has generally resulted in the high-intensity il-
lumination of an area much greater than necessary for sur-
gical procedures.
The high wattage required for the prior art lights
has generally required some provision to be made for cooling
the assembly, both to make it possible to safely handle the
light for focussing and the like, and to protect the structure
from heat damage. This has frequently been accomplished by
providing for air flow through the light structure, over and
1~9968~
around the light source, with the air thus heated being dis-
charged into the operating room at the back of the light.
Nevertheless, substantial heat radiation has often been ex-
perienced by operating room personnel, requently producing
unpleasant working conditions or placing an excessive burden
on operating room air conditioning and filtering systems.
While convection cooling may be more or less ef-
fective in cooling surgical lights, it frequently creates
other problems in that dust particles are carried into the light
assembly and collect on reflectors, light sources, and the
like, making it necessary to disassemble the structure for
cleaning at frequent intervals. This not only is a time-
consuming task, but also may result in damage to the delicate
reflective surfaces.
In overcoming the objections to and disadvantages
of the prior art surgical lights discussed above, an impor-
tant eature of the present invention resides in providing
a surgical light assembly which employs a relatively low-
intensity light source in combination with a system of fixed,
curved reflective surfaces and light-shielding and filtering
means ~hich provide the necessary illumination ~ore effi-
ciently and without objectionable shadows. Glare is substan-
tially reduced, and the possibility of emission of light rays
directly from the light source is substantially eliminated.
Heat radiation from the light is greatly reduced while light-
color balance is maintained by the use of reflectors and
filters. The light source is cooled by a heat sink having
a radiation surface exposed directly to the atmosphere at
~09~6~3Z
,
the back of the light so that convection currents thxough
the light assembly can be eliminated. The light can easily
and quickly be relamped, i.e., the light source removed and
replaced, from the rear of the light head assembly without
use of tools and without disturbing the fixed relationship
of the reflective surfaces or exposing the sealed reflective
surfaces to contamination. The unique arrangements of the
fixed curved reflectors results in an extremely compact, thin
light assembly which is light in weight and is easy to clean
and malntain. This fixed reflector arrangement, utilizing a
reflector configuration which concentrates the light rays and
focusses them into a relatively small but variable area for-
ward of the luminaire, or light head, is made possible by the
novel light source mounting structure.
An important contribution of the present lnvention
is achieved by the effective utilization of a light source
heat sink which removes heat directly to the back exterior
portion of the luminaire without interfering with the ability
to focus the light. Where the heat sink concept has been
utilized in the prior art, e.g., U.S. patent 3,348,036, it
has generally been necessary to rely on a ~inned structure
and/or internal, channelled convection currents to dissipate
the heat from the sink.
The parent application is directed to a light
assembly comprising, in combination,
a first reflector having a substantially parabolic
concave reflective surface,
a second reflector having an annular divergent external
~ -3-
~9968Z
" .
reflective surface,
support means mounting the first and second
reflectors in fixed spaced coaxial relation to one another
with their respective reflective surfaces in generally opposed
relation,
a third reflector having an annular divergent
internal reflective surface, such third reflector being
mounted on the support means in fixed coaxial relation with
and having its reflective surface extending in radially
outwardly spaced relation to the first and second reflectors,
the reflective surfaces on the first and third reflectors
being directed in the same general axial direction,
a light source,
mounting means supporting the light source within
the concave portion of the first refIector on the common
axis of the three reflectors, the mounting means including
actuating means operable to move the light source along
the common axis to focus the light on an area to be illum-
inated,
enclosing means enclosing the light source and
the reflective surfaces of the first and second reflectors, and
a heat sink in the form of a mass of metal having
a relatively high coefficient of thermal conductivity,
the r.lounting means supporting the light source
on and in heat-transfer relation with the heat sink, with the
heat sink extending through the enclosure means and having
a surface exposed to atmosphere externally of the enclosure
for dispersing into the atmosphere heat absorbed from the
light source,
the actuating means is operable to move the heat
sink and the light source mounted thereon along the common
axis of the reflectors.
~ 3a-
68Z
"~
The present divisional application is directed
to a light assembly comprising, in combination,
a light source, first, second and third curved
reflectors,
frame means supporting the first, second and
third reflectors in fixed coaxial relation relative to
one another to reflect light from the light source onto an
area to be illuminated,
the first reflector having a concave reflective
surface and being a cool reflector capable of transmitting
infrared light and reflecting substantially all visible
light, the second reflector having an annular divergent
external reflective surface, and the third reflector having
an annular divergent internal reflective surface, the
reflective surfaces on the first and third reflectors being
oriented in the same general axial direction and the third
reflector having its reflective surface extending in radially
outwardly spaced relation to the first and second reflectors,
an opaque light shield having a reflective surface
thereon,
light shield support means mounting the opaque
light shield in fixed relation to the light source and
between the light source and the second reflector with the
reflective surface o the opaque light shield facing the
light source to reflect back toward the first reflector
and the light source at least the major portion of light rays
emitted in the direction of the second reflector by the
light source, and
mounting means supporting the light source and
the opaque light shield within the concave portion of the
first reflector on the common axis of the three reflectors,
~ -3b-
~09g68Z
the mounting means including actuating means operable to
move the light source and the opaque light shield along
the common axis to focus the light on an area to be
illuminated.
Other features and advantages of the surgical
light according to the present invention will become more
apparent from the detailed description contained hereinbelow,
taken in conjunction with the drawings, in which:
Fig. 1 is a perspective view schematically illus-
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68~
trating the invention in use in an operating room environ-
ment;
Fig~ 2 is a plan view of the back of the light
assembly according to the invention, with portions broken
away and certain parts removed, to more clearly show other
parts;
Fig. 3 is a sectional view taken on line 3-3 of
- Fig. 2;
Fig. 4 is a ragmentary View, on an enlarged scale,
taken on line 4-4 of Fig. 2;
Fig. 5 is a sectional view taken on line 5-5 of
Fig 4;
Fig. 6 is a sectional view taken on line 6-6 of
Fig. 4; and
Fig. 7, located on the same sheet as Fig. l, is a
fragmentaryview, partially in section, showing the heat sink
andlight source in position for relamping.
In the surgical environment o~ Fig. 1, a t~o-unit
surgical light according to the present invention is indi-
cated generally by the reference numeral 10 and illustratedas being suspended from ceiling 12 above a patient 14 on an
operating table 16. A member 18 of the surgical team is sho~n
adjusting the position of one of the illuminators, or light
heads, 20, utilizing a sterile handle 22 which projects for-
wardly from the ront, or clean side, of the light assembly.
The light head 20 is preferably supported for pivotal movement
about a transverse axis by a yoke 24 which, in turn, is sup-
ported for rotation about an axis extending substantially
1L)9~6~
perpendicular to the transverse axis of the light head,
thereby providing a universal mounting enabling the light
to be positioned in the desired orientation relative to the
patient.
As seen in Fig. 2, the light head 20 is supported
on yoke 24 by a pair of tubular pin members (not shown) which
project inwardly through outer housing, or cover, 28 to en-
gage and support a pair of arms 30, 32 which project out-
wardly in opposite directions from the central ring-shaped
body 34 of a support yoke 36. An annular filter housing and
reflector support member 38 is mounted on and projects for-
wardly from the ring-shaped body 34 and is retained thereon
by a plurality of bolts 40. The inner peripheral portion
of a ring-shaped concaVe reflector 42 (Fig. 3) is rigidly
clamped between the annular member 38 and yoke body 34, with
the reflector extending outwardly and forwardly, i.e., in
the direction of projection of light from the light head 20,
from the filter support.
A focus support member 44 is also rigidly mounted
on the yoke ring 34. Focus support 44, as well as the support
yoke 36 and annular member 38, are each preferably integrally
formed, as by die casting, from a metal such as aluminum
having a relatively high coefficient of thermal conductivity.
These elements provide a strong yet lightweight frame struc-
ture which rigidly supports all the components of the light
head
The focus support 44 has a central hub portion 45
having a cylindrical bore 46 extending therethrough. Hub 45 is
1~9968Z
supported by three radially outwardly extending legs 48, 50,
52 which are rigidly secured to the yoke ring 34 as b~ bolts
54. A radially outwardly extending flange 56 integrally formed
on the focus support hub 45 defines a ledge 58 which provides
support for an inner flange portion 60 of a spun aluminum
outer cover 62. Outer cover 62 is rigidly mounted on ledge 58
by screws 64 extending through flange 60, thereby providing
for direct heat transfer between the focus support hub and the
outer cover.
The outer cover 62 terminates at its outer periphery
in a forwardly extendin~ annular skirt portion 66 which ex-
tends to a position adjacent the outer, rolled peripheral
edge 68 of reflector 42. ~he terminal edge 70 of the skirt 66
is joined with and sealed to the rolled edge 68 by a molded
resilient sealing strip 72. Thus, cover 62 and reflector 42
are spaced from one another a substantial distance, with the
space therebetween being substantially open and unobstructed
so that hot spotæ, or heat concentrations, are effectively
avoided.
The annular member 38 has three inwardly projecting
lugs 74 formed thereon at spaced intervals around its inner
periphery. The lugs 74 are contoured to engage and provide
; both radial and axial support for the beaded outer peripheral
edge 75 of a parabolic reflector 76. A number of pressure
- pads 77 are formed on the outer convex, non-reflecting sur-
face of reflector 76. Pressure pads 77 are each engaged by
a resilient block 78 supported, as by screws 79, 80 and s~rin~
clips 81, on the rearwardly facing surface o~ the ring 34.
11~9~8Z
Thus, the lugs 74 provide three-~oint supp~rt for the para-
bolic reflector 76, with the resilient blocks 78 retaining
the reflector in con~act with the lugs, so that stresses in
the reflector due to thermal expansion and contraction are
minimized~ The parabolic reflector 76 is a cold reflector,
i.e., one which reflects light within the visible range while
absorbing and transmitting infrared light. Heat is there-
fore directed toward the back of the light he~d assembly through
the reflector 76, while the useful, visible light is re-
flected toward the front. The substantial spacing betweenthe cover 62 and the reflectox 42 enables the wide distribution,
or scattering, of the infrared light so that it does not ex-
cessively heat any part of the structure.
The lugs 74 also support, on their f~rwardly directed
surfaces, a circular light filter plate 82 and a light dif-
fuser plate 83. Plates 82, 83 are retained in surface-to-
surface contact with one another and on the lugs by metal
clips 84 and bolts 85. The filter 82 absorbs and reflects
infra~ed light while transmitting light within the visible
range. Diffuser 83 acts to diffuse light passing through
the filter 82, thereby assuring against shadows or bright
spots in the area illuminated~ While filter 82 and diffuser
83 are shown as separate elements, they may be combined, if
desired, by providing a diffusion surface on the forward side
of the filter plate.
A cylindrical dust shield 86 having an inwardly
directed, integrally formed flange 87 on one end is mounted
on annular member 38 by a plurality of screws 88 extending
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-`` 1g~9968Z
through the flange 87. Dust shield 86 is substantiall~ trans-
parent and preferably formed from a s~nthetic re~in, or plas-
tic, material having a scratch-resistant outer surface which
is also resistant to cleaning solutions normally used to
clean non-sterilized equipment in operating rooms. All light
from the apparatus must pass through this cylindrical dust
shield in its path to the refleetor 42.
A handle support frame 89 is mounted by screws 90
on the end of the dust shield opposite the flange 87. Frame
89 extends radially inward and has mounted thereon a reflector
support 92 whieh, in turn, supports a generally conical re-
flector 94 in fixed coaxial relation to refleetors 42 and 76
and in position to refleet light laterally onto reflector 42.
Refleetor 94 is cireular in axial eross-seetion and flares
outwardly and forwardly from its rearwardly direeted end 95
whieh is mounted on the refleetor support 92. The outwardly
directed refleetive surface 96 is a surfaee of revolution
generated by rotating an outwardly eonca~e eurve about the axis
:- of symmetry.
A handle support 97, preferably formed from synthetic
resin or other material of relatively low thermal condueti-
vity, is mounted on the reflector support 92 as by a screw 98.
A spun metal light positioning handle 22 is threadably mounted
on the handle support 97, with the handle projecting out-
wardly from the light assembly in coaxial relation with the
reflector 94 to provide easy access for adjusting the position
of the light~ Handle 22 has a radially extending, integrally
formed flange 100 on its lnner end, with the flange 100 being
- 1~9~68Z
l~rge enough to provide a shield to pxevent the hand of a
person adju~ting the light from coming into contact with a
non-sterile portion of the light assembly. Handle 22 can
readily be removed from the handle support for sterilizing.
Also mounted on the reflector support 92 is a com-
bination light shield and cover plate 102 which ovexlies the
handle support frame 89. The plate 102 has a rearwardly ex-
tending peripheral skirt portion 104 which overlies and extends
in outwardly spaced relation to the forward end of the dust
shield 86, with an inwardly extending flange 106 extending
radially inward from the skirt 104 to engage the outer peri-
phery of the dust shield. This flange 106 is positioned rela-
tive to the conical reflector 94 and the outer edge of the
reflector 42 so as to act as a light shield preventing the
passage of light xays through the dust shield except in a
path which will strike the reflector 42. The cover plate 102
cooperates with the dust shield 86, the annular member 38,
reflector 42, and rear cover 62 to effectively seal the in-
; terior of the light head assembly to prevent convection cur-
rents therethrough and to exclude dust particles.
The transparent plastic dust shield 86 provides the
sole support for the reflector 94, adjustment handle 22 and
the light shield and cover plate 102. This arrangement eli-
minates shadows or blind spots which could result from inter-
nal structural supports.
A second light shield assembly 108 is positioned
within the enclosure of the light assembly and supported be-
tween the dust shield 86 and the annular member 38. The light
~ ~9~682
shield assembly 108 is constructed ~rom ~n an~le member 110
and a channel 112 assembled together to provide a rigid,
lightweight annular ring having inner and outer light-limiting
edges 114, 115, respectively, which are accurately positioned
and clearly defined to limit the escape of light to those
rays which strike the reflector 42 at an angle to be reflec-
ted onto the area to be illuminated. The plate 102 and light
shield 108 cooperate to essentially eliminate scatter light,
i.e., light other than that focussed onto the area to be il-
luminated. Further, these elements are spaced from one ano-
ther, along the axis of the fixed reflectors, and cooperate
to shield all but a relatively short axial length, or narrow
annular band, of the cylindrical dust shield 86. All of the
light escaping the enclosed structure must be reflected from
the external surface of reflector 94 through this narrow band
onto the substantially greater surace of reflector 42. This
is accomplished by concentrating the light rays, in a crossing
pattern, in the area of the exposed narrow annular band o the
dust shield in a manner similar to that disclosed in Figures
3 and 4 of allowed U.S. patent application Serial No. 496,166,
assigned to the assignee of this application.
Light from the light head assembly is produced by
a light source which preferably is in the form o a small
metal halogen or other suitable light bulb 120 supported on
- the common axis of reflectors 42, 76, and ~4 and within the
parabolic concavity of reflector 76. As illustrated, the
bulb 120 may have its base 122 plugged directly into a socket
123 carried by heat sink 124 and retained thereon by metal
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1~ 6~3Z
mounting ring 125. Ring 125 is mounted directly on and forms
a part of heat sink 124. The body of heat sink 124 is in the
form of a relatively large mass of metal such as aluminum
having a relatively high coefficient of thermal conductivity
to enable it to absorb heat directly from the base 122 o the
light bulb 120. The heat sink 124 has a radially enlarged
flange or cap 127 on its outer end, with the cap 127 having
its outer surface forming, in-effect, a continuation of the
outer surface of the rear cover 62.
Heat sink 124, with bulb 120 mounted thereon, is
supported in a guide sleeve 128, which, in turn, is mounted
for sliding movement within the cylindrical bore 46 of focus
support 44. As seen in Figs. 4-6, manually operable actuating
means are provided for adjusting the sleeve and the structure
supported therein along the cylindrical bore. This actuating
means includes a short axially extending gear rack 130 formed
on the outer surface of guide sleeve 128, with the rack 130
projecting outwardly through an axially extending slot 132
in central hub 45. A stub shaft 134 is journalled on the
focus support 44 and supports a pinion gear 136 in position
to mesh with the rack 130. Shat 134 is connected to one end
of a flexible drive shaft 138 for rotation thereby to drive
the guide sleeve 128, and the heat sink and light bulb carried
thereby, along the axis of the parabolic reflector 76. A
. resilient ball detent assembly 140 carried by the heat sink
124 is positioned to engage a slot 142 in guide sleeve 128 to
releasably retain the guide sleeve and heat sink in assembled
relation.
9~36~Z
The inner surface of the guide sleeve 128 is pre-
ferably in direct heat transfer contact with the adjacent sur-
face of the heat sink, and the external surface of the guide
sleeve is in direct heat transfer contact with the internal
surface of cylindrical bore 46 so that a portion of the heat
absorbed by the heat sink may also be transferred to the guide
sleeve and into the focus support, as well as to the external
cover 62, by conduction. Inwardly directed tongues 143 on
the inner surface of sleeve 128 cooperate with grooves 144 on
the adjacent surface of the heat sink to prevent relative
rotation therebetween and to assure assembly in the same
relative orientation each time the unit is disassembled. To
increase heat transfer from the base of the bulb to the heat
sink, the retaining ring 125 can have integrally formed ex-
tensions 126 disposed closely adj~cent two opposite sides of
the rectangular base 122 of the bulb, leaving the remaining
two sides exposed for easy access to facilitate removing and
replacing the bulb, a procedure generally referred to as re-
lamping.
Flexible shaft 138 has its other end connected to
a focussing handle 145 mounted on the outer periphery of the
skirt portion 66 of outer cover 62. Preferably, shaft 138
and handle 145 are connected through a resilient detent, or
stepping switch assembly 146 which provides a readily dis-
cernible positioning guide for indicating the location of the
heat sink and the light source and consequently an indication
o~ the focus of the light assembly. This stepped positioning
of the focus handle enables focussing by feel with minimum
9~3~82
disruption of concentration during a surgical procedure
As most clearly seen in Flg. 3, the light bulb 120
projects through a central opening 147 in reflector 76. The
bulb 120 is of the type having a relatively small, compact
filament 148 providing, for practical purposes, a point source
within the bulb envelope so that movement of the bulb along
the parabolic axis of reflector 76 affects the focus of the
light assembly, enabling easy adjustment of the area illumi-
nated and intensity of illumination by positioning the handle
145. An elongated, non-sterile light head positioning handle
or rod 149 is also mounted on the skirt 66, to facilitate
positioning the light head by non-sterile personnel, thereby
avoiding possible contamination of the sterile handle 22. The
handle 149 extends outwardly from and along a segment of the
skirt 66 in position to engage the yoke 24 and prevent the
light head from being rotated completely about the axis of
arms 30, 32. Also, the end portions of handle 149 first en-
gage the yoke 24, so that the focussing handle 145 is protected
and is always accessible.
To further reduce the amount of infrared contained
in the light which is emitted from the front of the light head
assembly, a shallow, generally cylindrical or cup-shaped retro-
; reflector 150 having a reflective inner surface is mounted
on the guide sleeve 128 by slender support rods 152 and
screws lS4 (see Fig. 2)~ The support rods 152 extend through
the openin~ 147 in reflector 76, in closely spaced relation
to the ceramic base 122 of the light bulb 120 so that the
retroreflector moves axially with the light bulb upon focussing
~ 13 -
~ LJ9~68Z
adjustment. The light filament 148 of the bulb is positioned
centrally of and closely adjacent the open top of the retro-
reflector so that light rays emitted directly from the filament
in the forward direction are reflected back toward the cold
parabolic reflector 76. Thus, essentially all light passing
through the filter 82 and diffuser 83 and striking the re-
flector 94 has been reflected by the cold reflector 76 and
also filtered through the filter 82 so that infrared light has
been effectively filtered out before the light can escape from
the assembly.
The infrared light transmitted through the cold
reflector 76 is absorbed by structural members of the light
head such as the inner surface of the back cover 62, the focus
support 44, and the inner support yoke 36. Heat from the
cover 62 may be radiated from the back of the light, or re-
moved from the cover by convection currents flowing over the
outer peripheral and back surface of the light. Similarly,
heat absorbed by the heat sink from the base of the bulb may
be dissipated from the back of the light, through the en-
larged flange 127 both by radiation and convection ~owever,since the light bulb is essentially sealed within the enclo-
sure of the light head assembly, convection currents through
the assembly are eliminated and the entire optical system
within the enclosure remains clean and uncontaminated, thereby
eliminatin~ the necessity for frequent cleaning o~ the inter-
ior of the light by maintenance personnel. The external sur-
face is substantially smooth and can readily be cleaned by
merely wiping down the exposed surfaces with an approved
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1 ai99682
cleaning solution. The open ~rame support structure within the
enclosure eliminates hot spots near the light source. At the
same time, this structure assists in the removal of heat,
thereby prolonging the life of the bulb.
Electrical current is supplied to the light bulb
through conductors or wires 155 extending through conduit 156
from the hollow interior of the arms of yoke 24 and the over-
head support assembly. The ends of the wires 155 are fixed
in the lamp socket 123 and the socket is secured and sealed
by a suitable high temperature pottin~ material 15fl. The
wires 15S extend upwardly through a channel 160 of the cen-
tral hub 45 of the focus support and are coiled around the
heat sink, beneath the overhang o the flange 127 to enable
the heat sink and light bulb to be withdrawn from the guide
sleeve 128 to provide access to the light bulb as shown in
Fig. 7. This is accomplished by rotating the pinion 136 in a
clockwise direction as viewed in Fig. 5 to thereby project
the heat sink flange rearwardly beyond the external surface of
the back cover 62. The ~lange 127 is then manually grasped
and pulled rearwardly to disengage the ball detent assembly
140 from the slot 142 in the guide sleeve, permitting the
bulb to be withdrawn through the central opening 147 in the
parabolic reflector 76. However, the retroreflector, being
mounted on the guide sleeve, remains within the light assembly
- when the light bulb and heat sink axe removed. This enables
very quick relamping, from the rear of the light, by un-
skilled personnel, without the disruption or contamination
of the optics or other internal parts of the light assembly.
- 15 -
~9~6~3;2
. . ~
As previously indicated, reflector 42 curves out-
wardly and forwardly from its inner peripheral mounting to
terminate in an outer edge 68. The laterally-directing re-
flector 94, which has a maximum diameter less than the minimum
diameter of the reflective surface of reflector 42, is mounted
within the axial limits of reflector ~2. Also, reflector 76
is mounted with the open forward end forward of the central
opening in reflector 42, with the vertex of the reflector ex-
tending rearwardly through the opening. This makes possible
the very compact arrangement of the three reflectors which
focus the light onto a relatively small, well-defined area.
The annular light beam from reflector 42 converges, with the
light rays merging and crossing within the focussed beam to
greatly reduce shadows.
By mounting the light bulb, per se, for movement
along the common axis of the three curved reflectors, the
light can readily be focussed while maintaining all of these
reflectors in a fixed position. Further, by concentrating
the useable light in a manner to be focussed directly on the
area to be illuminated, thereby substantially eliminating
scatter light which serves no useful purpose, a relatively
small light source may be employed. In tests of the light
in hospital operating rooms during actual surgical procedures,
it has been found that a metal halogen light having a rating
of 200 watts at 30 volts produced ample illumination for all
surgical procedures, and in fact was frequently operated at
less than maximum rated voltage. This low power consumption
not only makes the light more economical to operate, but also
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1L)996~3Z
reduces the amount of heat generated. The e~fective infrared
filter system, coupled with the novel heat sink structure,
concentrates this heat in the back of the light where it is
dissipated into the atmosphere.
A production model liyht assembly according to the
present invention has been subjected to extensive laboratory
testing. The complete li~ht head 20 weighed only approxi~ately
20 pounds, and the reflector 42 had a maximum diameter o~
22 inches. The total thickness of the unit, measured ~long
the common axis of the reflector~, rom the back o~ rear
cover 62 to the forward, outer rim 68 of reflector 42 was
only approximately 8 1/2 inches. A metal halogen light bulb
having a 200 watt rating at 30 volts was used. The focus
handle detent 146 had three positions to provide small, me-
dium and large circular patterns which were 4", 6", and 8 3/4",
respectively, in diameter, measured in a focal plane 42 inches
in front of the outer rim of reflector 42. The intensity of
the light at the center of these patterns, for various vol-
tages, was measured as follows:
~'
Voltage Li~ht intensity in ~t. Candles
_ Small Medium Large
22 3 ,aoo 1535 695
23 3,500 1870 809
24 4,000 2165 980
4,600 2525 1098
26 5,279 3700 1264
27 6,033 3252 1301
28 6,712 3700 158~
29 7,500 4159 1804
8,300 4680 2072
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1~9~6F~Z
The maximum intensities listed above ~or the center
of each pattern decreased to substantially zero outside a
nine-inch diameter pattern. The intensity variation is rela-
tively slight near the center of the patterns, then increases
rapidly. The point at which the rapid decrease in intensity
occurs varies with the focal position of the bulb, and is at
a greater distance from the center when the bulb is positioned
for a larger pattern. The size of the pattern is determined
by the point at which the light intensity drops to 20 per cent
of the maximum at the center of the pattern. In each case,
this 20 per cent level coincides very closely with the point
at which the sharp decrease in intensity occurs.
A further and important advantage of the elimina-
tion of scatter light is the substantially complete elimina-
tion bf glare. The light can be viewed from any position out-
side of the relatively small focussed light pattern directly
in front of the light head without seeing the light source,
either directly or indirectly. Thus, the surgeon can locate
the light in the position most advantageous for the surgical
procedure with complete confidence that the sight of other
members of the team is not being impaired.
Tests to determine the heat level of light from
the above-described production light we~e also conducted. It
was determined that, for a median intensity of 4,000 foot
- candles, the heat was only 13,000 microwatts per sq. cm. This
very low level of heat is hardly discernible to the naked
skin and contrasts greatly with the heat levels common in
prior art surgical lights of this type.
~9968Z
While the preferred embodiment of the invention
has been described, it is understood that various modifica-
tions and changes may be employed without departing from the
invention. Thus, for example, while each of the main reflectors
in the light head have been illustrated as being compound
curved reflectors, it is believed that one or more might be
a simple curved structure, for example, a conical reflector,
with the other reflectors being appropriately modified to
provide the desired illumination pattern for the various
focus positions of the movable light source. Accordingly,
while a preferred embodiment has been described in detail,
I wish it understood that I do not intend to be restricted
solely thereto, but rather that I do intend to include all
embodiments thereof which would be apparent to one skilled
in the art and which come within the spirit and scope of
my invention.
..~
-- 19 --
..'
