i have an engineering lab due in 4 hours

you have to watch a video and read the United States patent documents. and answer the questions. and I post my data just in case you need them for one of the questions.

United States Patent

USOO7147343B2

(12) (10) Patent No.: US 7,147,343 B2
Chapman (45) Date of Patent: Dec. 12, 2006

(54) FLASHLIGHT 4,623,957 A 1 1/1986 Moore et al.
4,875,147 A 10, 1989 Auer

(75) Inventor: Leonard T. Chapman, North 4.947,291 A 8, 1990 McDermott
Hollywood, CA (US) 5,138,538 A 8/1992 Sperling

5.351,330 A * 9/1994 Jongewaard …………….. 385.93
(73) Assignee: Chapman/Leonard Studio Equipment, 5,422,798 A 6/1995 Osiecki et al.

North Hollywood, CA (US) 5,594.433 A 1/1997 Terlep
5,630,661 A 5, 1997 Fox

(*) Notice: Subject to any disclaimer, the term of this 5,838,024. A 1 1/1998 Masuda et al.
patent is extended or adjusted under 35 5,865,529 A 2, 1999 Yan
U.S.C. 154(b) by 130 days. 6,007,218 A 12/1999 German et al.

(21) Appl. No.: 10/397,766 (Continued)

(22) Filed: Mar. 25, 2003 FOREIGN PATENT DOCUMENT

S

(65) Prior Publication Data GB 2216998 10, 1989

US 2004/O190299 A1 Sep. 30, 2004
OTHER PUBLICATIONS

(51) Int. Cl.
F2/4/04 (2006.01) Combined International Search Report and Written Opinion of the

International Searching Authority for International Application No.
(52) U.S. Cl. …………………. 362/187:362/188; 362/250; PCT/US2004/08472, dated Sep. 23, 2005.

362/800

(58) Field of Classification Search ……………. 362/.394, (Continued)
362/167, 169,170, 174, 178, 187, 188, 196, Primary Examiner—Sandra O’Shea
362/197, 199, 202, 227, 240, 250, 372,326, nary 5633.33.26.27.2s. 800 Assistant Examiner Guiyoung Fi

See application file for complete search history. (74) Attorney, Agent, or Firm—Perkins Coie LLP

(56) References Cited (57) ABSTRACT

U.S. PATENT DOCUMENTS

1478,282 A 12, 1923 Hunter
1.591,627 A 7/1926 Hopkin

s

1,595,146 A 8, 1926 Ford
1,603,272 A 10, 1926 Eaton
2,215,900 A 9, 1940 Bitner …………………… 362,309
2.249,689 A 7, 1941 Gelardin
2,313,356 A 3, 1943 New
2,347,532 A 4/1944 Yardeny
2.435,689 A 2f1948 McCabe
3,535,282 A 10/1970 Mallory
3,800,136 A 3, 1974 Edelson
4,577,263. A 3/1986 Maglica
4,605,994 A 8/1986 Krieg

A flashlight has a lens moveable relative to an LED. The
beam of light provided by the LED can be focused and
provides a uniform light pattern across the range of focus.
The lens is Supported on a front housing section and the LED
is Supported on a back housing section threaded onto the
front housing section. Twisting the front housing section
closes a switch providing power to the LED, to turn the
flashlight on. Twisting the front housing section also adjusts
the focus of the beam. A timer circuit within the flashlight
turns the flashlight off after a selected time interval, to
preserve battery life.

7 Claims, 11 Drawing Sheets

US 7,147,343 B2
Page 2

U.S. PATENT DOCUMENTS 6,866,401 B1* 3/2005 Sommers et al. ……….. 362,268
6,957,897 B1 10/2005 Nelson

6,013,985 A 1/2000 Green et al. 2002fOO67608 A1 6/2002 Kruse et al.
6,086,220 A 7/2000 Lash et al. 2002fOO93818 A1 7, 2002 Mele
6,095,661 A 8, 2000 Lebens et al. 2002/0149930 A1 10, 2002 Parker
6,142,650 A 1 1/2000 Brown et al. 2003/O123254 A1* 7/2003 Brass et al. …………….. 362,231
6,220,719 B1 * 4/2001 Vetorino et al. ………… 362,192 2004/O1308.92 A1 7, 2004 Galli
6,249,089 B1 6/2001 Bruwer 2004/O140771 A1 7, 2004 Kim et al.
6,296,367 B1 10/2001 Parsons et al. 2004/0240201 Al 12/2004 Rausseck ……………….. 362,171
6,345,464 B1 2/2002 Kim et al. 2005, 0122714 A1 6/2005 Matthews et al.
6,394,630 B1 5, 2002 Skidmore et al. 2005. O157492 A1 7, 2005 Chui
6,398,383 B1* 6/2002 Huang …………………… 362,202
6,485,160 B1 1 1/2002 Sommers et al. OTHER PUBLICATIONS
RE38,014 E * 3/2003 Bieberstein …………….. 362,206
6,527.419 B1* 3/2003 Galli …………………….. 362,308 Combined International Search Report and Written Opinion of the
6,612,714 B1 9, 2003 Morre et al. International Searching Authority for International Application No.
6,642,667 B1 11/2003 Avis PCT/US2005/28831, dated Mar. 14, 2006.
6,736,531 B1 5, 2004 Wallach Mag-lite Brochure: Anatomy-Mini Maglite. (Jan. 1, 2001).
6,761.467 B1 7/2004 Matthews et al. AviShop Brochure: LED Flashlight with Magnifier Lens. Web
6,793,366 B1 9, 2004 Chun Archive.org (May 25, 2002).
6,841,941 B1 1/2005 Kim et al.
6,854,859 B1 2/2005 Cooper et al. * cited by examiner

U.S. Patent Dec. 12, 2006 Sheet 1 of 11 US 7,147,343 B2

U.S. Patent Dec. 12, 2006 Sheet 2 of 11 US 7,147,343 B2

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U.S. Patent Dec. 12, 2006 Sheet 11 of 11 US 7,147,343 B2

Fig. 20

US 7,147,343 B2
1.

FLASHLIGHT

BACKGROUND OF THE INVENTION

The field of the invention is flashlights. More specifically,
the invention relates to a portable hand held battery powered
flashlight. For many years, flashlights have used batteries,
specifically, dry cells, to power an incandescent bulb.
Reflectors around or behind the bulb have been provided to
help direct light from the bulb. More recently, with the
development of light emitting diodes (LEDs), in some
flashlights the incandescent bulb has been replaced by an
LED. Use of an LED in place of an incandescent bulb as a
light source in a flashlight has several advantages. Initially,
LED’s use less power than incandescent bulbs. As a result,
battery life in an LED flashlights can be greatly extended. In
addition, LEDs are manufactured with specific light emis
sion directivity. Unlike an incandescent bulb, which radiates
light in all directions, LEDs emit light in specific directions,
or within a specific angle. Accordingly, for spot illumination,
which is the most common use for flashlights, the directivity
of LEDs is advantageous. LED’s also have an operating life
which is far longer than that of most incandescent bulbs.
Consequently, the disadvantages of bulb burnout or failure,
and the need to replace bulbs relatively frequently, are
largely avoided.

While use of LEDs in flashlights have several advan
tages, design challenges remain. In particular, the ability to
achieve a uniform beam of light under a wide range of
conditions has yet to be achieved with existing flashlights,
regardless of whether the light Source is an LED, an incan
descent bulb or another light source. The directivity (in
cluded angle) of existing LEDs is not sufficiently narrow for
lighting distant from the flashlight. Even with the most
directional LEDs, having a directivity angle of about 15°.
the emitted light becomes very faint more than a few feet
away from the LED. For various reasons, the light beam of
virtually all flashlights is not uniform. The intensity of light
in the beam varies. Generally, this variation appears as
lighter and darker areas of the beam. Some flashlights
produce a beam having an irregular shape, and decreased
lighting efficiency, rather than a nearly perfect circle of
uniform light.

In the past, several flashlights, especially flashlights hav
ing incandescent bulbs, have included beam focusing fea
tures. In these types of flashlights, typically a reflector
behind or surrounding the bulb is moved relative to the bulb.
to change the light beam pattern or to focus the beam. While
beam focusing is a useful feature in these types of flash
lights, generally, the shape or uniformity of the beam
changes as the beam is focused. These types of flashlights
are unable to maintain uniform light beam quality over an
entire range of focus. As a result, the light beam typically has
dark spots and appears dimmer, and the quality of the light
beam, in terms of field of illumination, is degraded.

Another drawback with battery powered flashlights is of
course the limited life of batteries. While use of LED’s can
greatly extend battery life, the traditional drawbacks asso
ciated with batteries have not been fully overcome. Even
with LED flashlights, prolonged use will drain the batteries.
Most flashlights have an on/off switch as the only control.
Accordingly, if the switch is inadvertently left on, the
batteries will be drained. Thus, to maintain the flashlight in
a useable condition, the user must remember to turn the
flashlight off. While seemingly a simple step, it is often
overlooked, especially where the flashlight is carried from a
dark location into a bright location, where there are exten

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45

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sive distractions to the user, or where the flashlight is used
by young children. To overcome this disadvantage, various
flashlights having automatic shut off features have been
proposed. However, few, if any of these proposals have
found widespread success, either due to design, operation,
manufacturing, cost and/or other reasons. In certain uses or
circumstances, it is important that the automatic shut off
feature be turned off entirely, so that the flashlight is
switched on or off manually. This added requirement pro
vides an additional engineering challenge in flashlight
design.

Flashlights have been adapted for use in extreme envi
ronments. For example, diving or underwater flashlights
have been designed to operate in an undersea environment
of high water pressure, low temperature, corrosive seawater,
etc. While these types of environmental flashlights have met
with varying degrees of Success, engineering challenges
remain in providing a flashlight which can reliably withstand
extreme pressures, high and low temperatures, corrosive
environment, shock, vibration and other adverse environ
mental conditions.

Accordingly, it is an object of the invention to provide an
improved flashlight.

SUMMARY OF THE INVENTION

In a first aspect, a flashlight has an aspheric, plano convex,
or other suitable lens for focusing light from an LED
powered by batteries. As the LED has low power consump
tion useful battery life in the flashlight is greatly extended.
The lens helps to provide a uniform and bright light beam,
without the need for a reflector.

In a second aspect, the lens is moveable relative to the
LED, allowing the beam to be focused. Preferably, the
flashlight housing has a front section Supporting the lens,
and a rear section supporting the LED. With the rear section
advantageously threaded into the front section, turning or
twisting the front section focuses the light beam.

In a third and separate aspect, a flashlight has an elec
tronic timer circuit which automatically turns the flashlight
off after a preset interval. As a result, battery power is
preserved, even if the flashlight is inadvertently left on.
Preferably, the preset interval can be adjusted for a short
period of time. Such as 5-7 minutes, or for a longer period
of time, for example, 15 or 20 minutes. For specialized
requirements, the timer can be designed to turn off the
flashlight after a preselected interval, or the timer can be
disabled to provide continuous operation (until manually
turned off). The timer circuit is advantageously combined
with an LED as the light source in the flashlight.

In a fourth and separate aspect, a flashlight has multiple
lens on a lens base aligned with multiple LED’s or lamps.
Turning a first section of the flashlight causes the lenses to
move towards or away from the LEDs, to focus the light,
with the lenses remaining axially or optically aligned with
the LEDs. This design allows a flashlight having multiple
LEDs to focus the light provided by the LEDs.

Other further objects and advantages will appear from the
following written description taken with the drawings,
which show two embodiments. However, the drawings and
written description are intended as preferred examples, and
not as limitations on the scope of the invention. The inven
tion resides as well as sub combinations of the elements
described.

US 7,147,343 B2
3

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same element number indi
cates the same element in each of the views;

FIG. 1 is a front and side perspective view of the present
flashlight.

FIG. 2 is a side view of the flashlight shown in FIG. 1.
FIG. 3 is an exploded front and side perspective view of

the flashlight shown in FIG. 1.
FIG. 4 is an enlarged section view of the flashlight shown

in FIG. 1.
FIG. 5 is an enlarged exploded section view of the

flashlight shown in FIGS. 1 and 4.
FIG. 6 is a top view of the switch housing shown in FIGS.

3 5.
FIG. 7 is a section view taken along line 7 7 of FIG. 6.
FIG. 8 is a section view taken along line 8–8 of FIG. 6.
FIG. 9 is a section view taken along line 9–9 of FIG. 6.
FIG. 10 is a section view of the flashlight shown in FIGS.

1–5, with the front housing section in a fully extended
position;

FIG. 11 is a section view showing the flashlight in a fully
retracted or off position:

FIG. 12 is a section view showing installation of the
Switch housing tube.

FIG. 13 is a section view of an alternative embodiment;
FIG. 14 is a section view of another alternative embodi

ment,
FIG. 15 is an exploded section view of the flashlight

shown in FIG. 14;
FIG. 16 is an elevation view taken along line 16—16 of

FIG. 15:
FIG. 17 is an elevation view taken along line 17 17 of

FIG. 15:
FIG. 18 is an elevation view taken along line 18 18 of

FIG. 15:
FIG. 19 is a schematic illustration of the shut off timer

circuit in the circuitry module shown in FIGS. 3–5:
FIG. 20 is a schematic illustration of an alternative shut

off timer circuit for use in the circuitry module shown in
FIGS. 3 S.

DETAILED OF DESCRIPTION OF THE
DRAWINGS

Turning now in detail to the drawings, as shown in FIGS.
1 and 2 a flashlight 10 has a lens 14 within a front cap 12 on
a front housing section 16. A rear housing section 20 extends
into the front housing section 16. A housing ring 18 is
provided on the rear housing section 20 adjacent to the front
housing section 16. And end cap 22 on the rear housing
section 20 is removable to install or remove batteries from
the flashlight 10.

Referring now to FIGS. 3, 4 and 5, the front cap 12 has
a conical surface 30 at its front end 32. A seal groove 41 is
provided adjacent to the conical surface 30 on the front cap
12 as shown in FIG. 5. Screw threads 28 are provided on the
back end of the cap 12.

Referring to FIGS. 4 and 5, the lens 14 is preferably an
aspheric glass, plano convex, or other Suitable (depending
on LED selection and focal length) lens. The lens 14 has a
spherical front surface 34, and preferably a flat rear surface
36 facing the LED 50. A cylindrical or ring surface 38 at the
back end of the lens 14 seals against a seal element. Such as
an O-ring 40 in the seal groove 41 as shown in FIG. 5. The
lens 14 preferably has a focal length of 8–16, 10–14 or 12
mm. The lens is sufficiently thick enough to provide

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4
adequate strength to resist pressure equivalent to 9000 feet
of water. The center thickness is typically 5–6 millimeters.
The term “lens’ means an element that focuses or bends
light.

Referring to FIGS. 4 and 5, a lamp housing 42 having a
conical inside wall 44 is placed or pressed into the front cap
12, holding the lens 14 and O-ring 40 in place. The threaded
back end 28 of the front cap 12 is threaded into internal
screw threads 82 at the front end of the front housing 16. The
lamp housing 42 is longitudinally positioned within the front
cap 12 via a flange 46 at the back end of the lamp housing
42 stopping on the back end of the front cap 12. A front cap
O-ring or seal 48 seals the front cap 12 to the front housing
16.
The front housing 16 is threaded onto the rear housing 20

via internal threads 84 on the front housing 16 engaged with
external threads 104 at the front end of the rear housing 20.
The components described above (i.e., the front cap 12, lens
14, O-ring 40, lamp housing 42, and O-ring 48) are all
supported on (directly or indirectly) and move with, the front
housing 16.

Referring still to FIGS. 4 and 5, the LED, light source or
lamp 50 has anode and cathode leads extending into elec
trical contacts 52 in a switch housing 54. A microswitch 60
is supported within the switch housing 54. A plunger 56
extends from the microswitch 60 through and out of the front
end of the switch housing 54, with the plunger biased
outwardly against the back Surface of the housing 42. The
switch housing 54 is supported on or in the front end of a
switch housing tube 72. A rim or collar 64 contacts the front
end of the switch housing. The contacts 52 extend through
contact bores or openings 62 in the switch housing 54, as
shown in FIG. 8.
A circuitry module 70 within the switch housing tube 72

is electrically connected to the switch 60, and also to the
batteries 90 via a battery contact 76 extending through a tube
collar 74 at the back end of the switch housing tube 72. As
shown in FIG. 4, a housing seal 78 seals the front end of the
rear housing section 20 to the back end of the front housing
section 16, while still allowing the front housing section 16
to turn, and shift longitudinally (along a center axis of the
flashlight), as the front and rear housing sections are turned
relative to each other.
The rear housing section 20 has an open internal cylin

drical space for holding the batteries 90. In the embodiment
shown in FIGS. 4 and 5, three N size batteries are used. Of
course, different numbers and types of batteries may be used,
consistent with the requirements of the LED 50 and circuitry
module 70 provided. The front end of the rear housing
section 20 includes a seal groove 102 as shown in FIG. 5,
just behind the external threads 104, to hold and position the
housing seal 78. A stop 106 limits the rearward range of
travel of the front housing section 16 on the rear housing
section 20. A housing ring 18 is pressed onto the rear
housing section 20 and positioned adjacent to the stop 106.
At the back end of the flashlight 10, threads 98 on the end
cap 22 are engaged with rear internal threads 108. An end
cap seal or O-ring 92 within a groove 93 on the end cap 22
seals the end cap 22 against a recess 109 in the rear housing
section 20. A battery spring 94 grounds the negative terminal
of the rear most battery to the rear housing section 20, and
forces the batteries 90 into contact with each other and with
the battery contact 76. A hole 96 through the end cap 22
allows the flashlight 10 to be mounted on a key chain, key
ring or wire.

FIG. 13 shows an alternative embodiment having a
shorter length than the flashlight shown in FIGS. 1–5. The

US 7,147,343 B2
5

shorter length is provided by having a shorter rear housing
section 122 and using shorter batteries 124. The flashlight
120 in FIG. 13 is otherwise the same as the flashlight 10
shown in FIGS. 1–5.

The LED 50 is preferably an NSPW51OBS, with a 50°
directivity angle available from Nichia Corporation, Tokyo,
Japan. The directivity angle generally is the included angle
of the solid cone of light emanating from the LED. Outside
of this solid conical angle, there is little or no light. Within
the directivity angle, with most preferred LEDs, the light is
reasonably uniform, with some decrease in intensity near the
sides or boundary of the angle. The directivity angle is
specified by the LED manufacturer. Other more powerful
LEDs will soon be available, which may affect lens selec
tion. The lens 14 is preferably an aspheric 01LAG001, 2 or
111 (having a focal length of 12 mm) available from Melles
Griot, Carlsbad, Calif., USA. A plano/convex lens or other
lenses may also be used. The lens preferably has a high level
of strength to better resist pressure, Such as water pressure
when used underwater. In general, the front or outwardly
facing Surface of the lens will be curved, domed, or convex,
as shown in FIG. 4, to better resist pressure forces.

Experimentation with LEDs and lenses reveals that, in
terms of flashlight performance, a specific relationship exists
between the directivity angle A of the LED and the focal
length of the lens f (in millimeters). For preferred perfor
mance characteristics, the ratio of A/fis within the range of
3.5 to 6.5, preferably 4 to 6 or 4.5 to 5.5, and more preferably
approximately 5.

FIG. 4 shows the flashlight 10 in the off position. The
front housing section 16 is threaded onto the rear housing
section 20, until it comes to the stop 106. In this position, the
plunger 56 is almost entirely within the switch housing 54,
causing the switch 60 to be in the off position. Electrical
power provided from the batteries 90 through the battery
contact 76 and circuitry module 70, as well as through the
rear housing section 20, is provided to the switch 60. The
switch 60 is also connected to the LED, as shown in FIG. 19.
As the switch 60 is in the off position, no power is provided
to the LED. To turn the flashlight 10 on, the front housing
section 16 is turned (counter clockwise in FIG. 1) causing it
to move forward via the interaction of the threads 104 and
84. As the front housing section 16 moves forward, the front
cap 12, lens 14 and the lamp housing 42 move with it. The
LED 50, switch housing 54, plunger 56, switch 60 circuitry
module 70 all remain in place, as they are supported within
the switch housing tube 72 which is fixed to the rear housing
section 20.

As the LED or light source 50 and lamp housing 42 move
away from the switch housing 54, the plunger 56, biased by
spring force in the switch 60 also moves forward or out
wardly. This movement causes the switch 60 to move into an
on position. In the on position, the electrical power is
provided to the LED 50. To focus the light from the LED or
light source 50, the user continues to turn the front housing
section 16. This increases the spacing “S” between the lens
14 and the LED 50, allowing light from the LED to be
focused to a desired distance. A position stop 130 on the
front end of the switch housing tube 72 prevents the front
housing section 16 from separating from the rear housing
section 20. When the front housing section 16 is turned to its
maximum forward position (where further forward move
ment is prevented by the stop 130), the lens 14 focuses the
light to a maximum distance.

Referring momentarily to FIG. 12, the switch housing
tube 72 is installed from the front end of the front housing

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section. The threaded section 73 of the switch housing tube
72 engages with the threads 82 on the front housing section.
The spanner tool 75 is inserted through the back end and is
used to tighten the switch housing tube 72 in place. The rim
or stop 130 at the front end of the switch housing tube acts
as a mechanical stop to prevent the front housing section
from separating from the rear housing section.
The combination of the LED 50 and the lens 14 allows the

flashlight 10 to focus, and also to provide a narrow direct
beam of light. The focusing range of the lens 14 allows
filaments of the light source, which appear in the beam, to
be used as pointers or indicators. A light beam provided by
the flashlight 10 has minimal dark spots. In addition, the spot
pattern produced by the flashlight 10 is nearly a perfect
circle, throughout the entire range of focus. The LED or light
source 50 may be provided in various colors.

In general, light from the LED is focused by the lens, and
no reflector is needed. However, with some LEDs, use of a
reflector, in combination with a lens, may be advantageous.
If the LED used has a large directivity angle, for example,
60, 70, 80, 90 degrees, or greater, the lamp housing 42 can
also act as a reflector. Specifically, the interior curved or
conical Surface or wall 44 is made highly reflective, e.g., by
polishing and plating. The divergence angle of the wall 44.
or curvature, is then selected to reflect light towards the lens.
While in this embodiment the reflector (formed by the
Surface 44) moves with the lens, a fixed reflector, e.g.,
Supported on the Switch housing 64, may also be used.
The housing ring 18 and front cap 12 provide convenient

grip Surfaces for turning the front and rear housings relative
to each other to switch the flashlight 10 on and off, and to
focus the light beam. The housing seal 78 is the only
dynamic seal in the flashlight 10. The other seals are static.

Referring to FIG. 19, when the flashlight 10 is turned on
by twisting or turning the front and rear housing sections 16
and 20, the switch 60 closes, or moves to the on position.
Battery voltage 90 is then applied to the relay 150, causing
the relay to close. Consequently, current flows through the
LED 50 generating light. At the same time, the capacitor C1
begins to charge. When the Voltage V1 across the capacitor
C1 reaches a trigger level, it causes the output of the
amplifier 158 (which act as an inverter) to cause the tran
sistor 156 to switch the relay off or open. Power to the LED
50 is then interrupted, preserving the life of the battery 90.
To turn the flashlight 10 back on, the switch 60 is returned

to the off position by turning the front and rear housing
sections in the opposite directions. With the switch 60 in the
off position, the capacitor C1 discharges through the resister
R1, returning V1 to Zero, and effectively resetting the timer
70. When the switch 60 is moved back to the on position,
power is again Supplied to the LED, and the flashlight is
turned on to provide light. The timer circuit 70 reset to turn
off power to the LED after a preset interval. The preset
interval is determined by selecting the value of C1. By
providing one or more additional capacitors 152 and a
capacitor switch 154, the time interval before shut off can be
adjusted, or selected from two (or more) preset values. The
switch 154 is on or in the switch housing 54, is typically set
by the user’s preference, and then remains in the shorter or
longer internal position. The second Switch position can be
a timer bypass option.

Turning now to FIGS. 14–18, in another flashlight
embodiment 200, three lamps or LED’s 50 are provided, and
a lens 14 is aligned and associated with each LED50. Except
as described below, the flashlight 200 is similar to the
flashlight 10 described above. A lens ring 202 and a lens base
204 have three openings 206 for receiving or holding three

US 7,147,343 B2
7

lenses 14. Each lens 14 is secured in place on the lens ring
202 within an O-ring 208. The lens ring 202 and lens base
204 are attached to each other by screw threads, adhesives,
etc., after the lenses 14 are placed into the lens ring 202.
Counterbores 209 extend into the back surface of the lens
base 204. Anti-rotation pins 210 extend from the switch
housing 212 into the counterbores. As the Switch housing
212 is fixed to the rear housing section 214, the lens ring 202
does not rotate with the front housing. The lenses 14 in the
lens ring can move longitudinally towards and away from
the LEDs, while staying aligned with the LEDs. The
switch housing 212 holds three LED’s 50, with each LED
aligned with a lens 14. A Teflon (Flourine resins) washer 214
between the front housing section 216 and the lens base
allows the front housing section 216 to rotate and slide
Smoothly against the lens base 204, as the front housing
section 216 is rotated to turn on or focus the flashlight 200.
Similarly, a low friction O-ring or seal 218 supports the lens
ring 202 within the front housing section 216, while allow
ing for rotational and front/back sliding movement between
them. A front cap 220 is sealed against the front housing
section 216 with an O-ring or seal 222.

In use, as the front housing section 216 is twisted or
rotated, it moves front to back via the interaction of the
Screw threads 104 and 84. The LED’s 50 remained fixed in
place. The lenses 14 move front to back, with movement of
the front housing section, but they do not rotate as the lens
ring 202 and lens base 204 are held against rotation or
angular movement by the pins 210. Consequently, light from
each of the three LED’s 50 can be focused with movement
of the front housing section 216. Of course, the design
shown in FIGS. 14–18 is suitable for use with 2, 3, 4 or any
number of additional LEDs.

Turning to FIG. 20, in an alternative timer circuit 250, the
switch 154 is removed and replaced with switch 254. The
switch 254, when closed, connects the LED 50 and the
resistor R4 directly to the battery 90. All of the other
components are bypassed. As a result, when the switch 254
is closed, the timer circuit 250 is inactive or disabled, and
illumination by the LED is controlled purely by the switch
60. This design is advantageous where the user wants the
flashlight to remain on until manually turned off using the
switch 60, which is actuated by turning the front housing
section. When the switch 254 is in the open position, the
timer circuit shown in FIG. 20 operates in the same way as
the timer circuit 70 shown in FIG. 19. With the Switch 254
open, the timer circuit 250 automatically turns the flashlight
off after a preset interval of time determined by the capaci
tors C1 and 152. The timer circuit 250 otherwise operates in
same way as the timer circuit 70, except as described above.

Referring momentarily to FIGS. 5 and 17, the switch 154
or 254 is set in the open or closed position by removing the
front cap 12, along with the lens 14, O-ring 40, and the lamp
housing 42 (which remain as a single Sub-assembly with the
lamp housing pressed into the front cap 12). Referring to
FIG. 6, an instrument, such as a small screwdriver blade, or
even a pen or pencil tip, is inserted through the access hole
57 in the switch housing 54 to set the switch 154 or 254 to
the desired position. The switch 154 can be set to a shorter
or a longer time interval before automatic shutoff. If the

10
15
25
30
35
40
45
50
55

8
switch 254 is used, the switch positions are automatic
shutoff mode (determined by the capacitors), or “permanent
on’ where the flashlight acts as a conventional flashlight
controlled entirely by the switch 60, and with no automatic
shutoff feature. Referring to FIG. 14, in the embodiment
200, the switch 154 or 254 is set by removing the front cap
220, along with the O-rings 208 and 222, the lens ring 202,
the lens base 204, and the lenses 14 (which remain as single
sub-assembly). The switch 154 or 254 is then readily
directly accessible.

Thus, a novel flashlight has been shown and described.
Various changes and modifications may be made without
departing without the spirit and scope of the invention. The
invention, therefore, should not be limited, except by the
following claims, and their equivalents.
What is claimed is:
1. A flashlight comprising:
a first housing section;
a second housing section attached to the first housing

section with screw threads:
a seal between the first and second housing sections;
a stop engageable against a Surface on the first housing

section to prevent the first housing section from sepa
rating from the second housing section by rotation of
the first housing section relative to the second housing
section;

a single LED supported on the second housing section;
a lens having a convex front Surface, with the lens axially

aligned with the LED and supported directly or indi
rectly on the first housing section adjacent to the LED,
and with the lens and the first housing section longi
tudinally moveable relative to the LED, to a position
where the spacing S between the LED and the lens is
less than the maximum thickness of the lens, to focus
light from the LED; and

the LED having a directivity half angle A, and the lens
having a focal length f, and with the ratio of A/f
between 3.5 degrees/mm and 6.5 degrees/mm.

2. The flashlight of claim 1 further comprising a lens base
on the front housing section with the lens aligned with the
LED, and with the lens base axially moveable with rotation
of the front housing, while maintaining the lens in alignment
with the LED.

3. The flashlight of claim 1 where the lens has a spherical
front surface.

4. The flashlight of claim 1 further comprising a reflector
adjacent to the LED, and with the LED between the reflector
and the lens.

5. The flashlight of claim 1 further comprising a front cap
attached to a front end of the front housing section, with the
lens secured within the front cap; a first seal between the lens
and front cap, and a second seal between the front cap and
the front housing section.

6. The flashlight of claim 1 with the lens having a focal
length of 8–16 mm.

7. The flashlight of claim 1 wherein the stop comprises an
annular rim.