Twist-on/twist-off flashlight with shock-mounted bulb assembly and redundant off-switching, particularly for use at the tip of police batons

Two, redundant, electrical switches in electrical series between a flashlight's battery and its bulb are simultaneously activated by an angular rotation between two sections of the flashlight's case. To implement one of the switches the functions of (i) force biasing and (ii) electrical conduction between a battery's terminal and the flashlight case are separated. Force biasing between battery and case transpires by a spring and washer which are, in combination, electrically non-conducting. Electrical conduction between battery and case transpires by another, separate, spring that is shorter than the force-biasing spring. Further, and independently, a removable and replaceable combination shock-mounted light bulb and reflector assembly includes (i) a wire-lead miniature light bulb of low inertial mass encapsulated within (ii) a shock-absorbing plastic matrix which is further sleeved in (iii) a strong metal which also presents a reflector surface precision aligned to the bulb. The entire assembly is easy to handle and exhibits superior (i) mechanical alignment, strength, and damage resistance, and (ii) electrical connectivity, when placed and replaced within a flashlight of complimentary construction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally concerns apparatus for coercive 
intervention--particularly batons and rugged flashlights --that are usable 
by law enforcement and like personnel to manipulate the environment, 
including human actors within the environment. 
The present invention particularly concerns a flashlight that is especially 
rugged in each of its (i) bulb mounting and its (ii) positive on/of f 
actuation (particularly by a twisting motion) so as to be mountable at the 
end of a police baton and thereafter usable by the police for all normal 
functions of both (i) the baton and (ii) the flashlight. 
2. Background of the Invention 
A police baton, having ancient antecedents in the simple club, is a classic 
weapon within the police arsenal. Police are trained in use of the baton. 
The baton is a useful device variously facilitating the inspection of 
items, the guidance or signalling of persons including suspects and other 
police, and the use of force against persons and objects. Modern batons 
are often made of metal, and may be telescoping such as is shown in U.S. 
Pat. Nos. 4,752,072 issued Jun. 21, 1988, and 5,110,375 issued May 5, 
1992. 
Meanwhile, criminals have always sought the obscuring cloak of darkness, 
and criminal activity generally peaks at night. Many forms of criminal 
activity that are currently, circa 1992, prevalent in the United States of 
America involve trade in illegal drugs, or criminals who have ingested 
illegal drugs. Because of the illegality of selling or consuming illegal 
drugs, both sales and consumption are commonly conducted during the hours 
of darkness, and in locations that are poorly illuminated. 
Still other, more traditional, criminal activities such as theft are common 
at night, and are commonly conducted with no or minimal illumination. 
Indeed, the crime of burglary was defined in the common law as 
unauthorized entrance into a dwelling house at night with an intention of 
thievery. This definition of the crime of burglary, and the severe 
punishments for its perpetration, recognize the special severity, and the 
special difficulties, of preventing or interdicting crime during the hours 
of darkness. 
Because of the responsibilities of the police to curb criminal activity 
during darkness, and in dark places, special, rugged, flashlights are 
commonly issued to police. The police flashlight has considerably improved 
during recent decades. Modern police flashlight cases are strong, and may 
be suitably used as clubs. The emitted light is considerably brighter, and 
is often longer-lasting, than was previously the case. The advent of 
quartz-halogen light sources has particularly benefitted the police 
flashlight, which is, in certain cases, desired to emit a very bright, 
nearly blinding, light beam. 
Police flashlights can, under certain circumstances, be used for signaling 
and for striking similarly to the uses of a police baton. 
Possibly because of the potentially similar uses of a police baton and a 
police flashlight, and because of the similar tubular shapes and elongate 
aspect ratios of both devices, it has been from time to time suggested 
that the functions of the two devices might combined. The combination of a 
police baton and a police flashlight is an interesting concept in that it 
could potentially increase the utility of both the baton and the 
flashlight. 
One unavoidable problem with the existing police flashlight, even one 
emitting a very bright light, is that the policeman holding the flashlight 
must identify his location. There is usually a time delay between a 
policeman's energizing of his/her flashlight and his/her visual fixation 
of any person or persons that may be within the flashlight's illuminating 
beam. There is a further time delay while the policeman, who may be 
attempting to aim his/her flashlight with a one hand while protecting 
himself/herself with a loaded weapon in the other hand, interprets the 
illuminated scene. During these time delays, which may be only momentary, 
the policeman is in jeopardy of being shot without warning by the 
party(ies) illuminated, or even by other parties who are still concealed 
by darkness. 
Because of these obvious risks, and tensions, the literal shining of light 
on criminal activity is, in America circa 1992, a hazardous activity. If a 
flashlight could be located at the end of baton then a policeman could use 
the flashlight beam to illuminate suspicious activities or objects while 
the source of the light beam was more substantially distanced from the 
policeman's body. If an illumination from the beam of a flashlight at the 
end of a police baton were to elicit a hostile response then the policeman 
would already, and conveniently, be armed with at least the baton. 
Alternatively, attachment or other integration of a flashlight with a baton 
facilitates and improves use of the flashlight because the flashlight may 
be more conveniently brought proximate to objects which are desired to be 
illuminated, or the flashlight may be inserted through small spaces into 
dark areas. 
Whether a police baton is hypothesized to incorporate the function of a 
flashlight, or a police flashlight is hypothesized to be reconfigured so 
as to more substantially incorporate the function of a baton, any quality 
consolidation of the functions of both devices presents certain 
challenges. 
A combination police baton and flashlight would desirably be fully as 
functionally capable as either a (i) police baton, or a (ii) police 
flashlight individually. In order to realize the baton function both the 
mechanical and electrical sections, including the bulb, of a flashlight 
must be so rugged, or hardened, so as to permit that the flashlight may be 
stuck against objects with great force without appreciable risk of 
failure. This must be accomplished without, in particular, making the 
electrical sections of a flashlight so large or so massive so as to 
detract from the normal aspect ratio, and balance, of a baton. Nonetheless 
to its occasional use for striking, a combination police baton and 
flashlight would desirably turn on and of f easily and reliably during all 
conditions and histories of use and misuse. 
Conversely, in order to realize a the function of a flashlight, a baton, 
especially a lightweight collapsible telescoping baton, must incorporate, 
or be integrated with, the function of a flashlight without a degrading 
its essential purpose. This likely requires, in particular, that neither 
the weight, strength, balance, rigidity, hardness nor grip (finish) of the 
baton should be appreciably altered. 
The present invention will be seen to concern certain improvements in 
flashlights. The improvements, although of general applicability to rugged 
flashlights such as are used by police, are particularly directed to 
making flashlights that are fully capable of being integrated with police 
batons in order to constitute a combination baton-and-flashlight 
apparatus, and weapon, having excellent characteristics, and 
effectiveness, in both its baton and its flashlight functions. 
SUMMARY OF THE INVENTION 
The present invention contemplates a flashlight having two, redundant, 
series-connected electrical switches in an electrical path between the 
flashlight's battery and its bulb. Both switches are simultaneously 
activated by angular rotation between two sections of the flashlight's 
case. Although each switch is highly reliable, the predominant failure 
mode of each is a "stuck on" condition. Because the two switches are in 
electrical series, both must fail "stuck on" before the flashlight is 
incapable of being turned off. 
The present invention further, and independently, contemplates a removable 
and replaceable combination shock-mounted light bulb and reflector 
assembly f or a flashlight. A wire-lead miniature is light bulb of low 
inertial mass--which miniature bulb would be difficult to handle and to 
electrically connect individually--is encapsulated within a 
shock-absorbing plastic matrix which is further sleeved in strong metal. 
The composite assembly, including a reflector surface precision aligned to 
the bulb, is easy to handle during placement and replacement within a 
flashlight case of complimentary construction. The assembly accords 
superior (i) mechanical alignment, support, shock isolation and damage 
resistance, and (ii) reliable electrical connectivity, of the bulb. 
In accordance with the first, electrical switching, aspect of the present 
invention, another, second, electrical on/off switch is added to a twist 
on/twist off flashlight that already possesses one on/off switch. 
Typically such a preexisting flashlight has a tubular case with two 
electrically-conducting sections. The two sections screw together along 
insulating surfaces until, the relative angular rotation between the two 
sections exceeding a predetermined first degree, electrically conductive 
surfaces upon the two sections are placed into electrical contact. A light 
bulb is located within a first end portion of the two-section tubular 
case. The bulb has two terminals, a first one of which is in continuous 
electrical contact with a first section of the two-section tubular case. A 
battery is located, and moveable, within an opposite end portion of the 
two-section tubular case. The battery also has two terminals. A spring 
force biases the battery for movement within the tubular case so that a 
first one of its two terminals is in continuous electrical contact with a 
second terminal of the light bulb. The spring also electrically connects 
the second terminal of the battery to the second section of the 
two-section tubular case. 
By this conventional construction any angular rotation of the flashlight's 
two sections that exceeds some predetermined first degree will place the 
two electrically-conducting sections of the tubular case into electrical 
contact. This contact completes an electrical circuit from the battery 
second terminal to the case second section to the case first section to 
the light bulb first terminal through the light bulb to the light bulb 
second terminal bulb back to the battery first terminal, energizing the 
light bulb from the battery and emitting light. This conventional 
construction, and operation, of a flashlight where an angular rotation of 
two flashlight sections relative to one another accomplishes the 
electrical on/off switching of the flashlight, is called "twist on/twist 
off". 
In accordance with the first, electrical switching, aspect of the present 
invention, the spring between the battery's second terminal and the second 
section of the tubular flashlight case is improved. Namely, the force 
biasing and electrical conduction functions of the spring are separated. 
An electrically-nonconducting member, normally a metal coil spring and 
insulating washer, serves to force bias the battery for movement within 
the tubular case so that the first one of its two terminals is in the 
continuous electrical contact with the second terminal of the light bulb. 
Meanwhile, an electrically-conducting member, normally another metal coil 
spring located coaxially with the first metal coil spring but insulated 
therefrom, electrically connects the second terminal of the battery to the 
second section of the two-section tubular case only when the case's two 
sections are angularly rotated relative to one another to greater than a 
predetermined second degree. The electrically-conducting member is 
normally a metal coil spring not so as to provide a biasing force to the 
movement of the battery within the case (which force is provided by the 
first coil spring of the electrically non-conducting member), but only so 
as to produce such a wiping force as permits good electrical contact. The 
reason why the electrically-conducting member, or second metal coil 
spring, makes electrical contact between the second terminal of the 
battery and the second section of the tubular case only upon sufficient 
rotation (to the predetermined second degree) of the case's two sections 
is simple. The second coil spring is shorter than the first coil spring. 
The two sections of the case must be screwed together, and the first coil 
spring compressed, to a sufficient degree before the second coil spring 
will span the entire gap between the second terminal of the battery and 
the second section of the tubular case. 
Accordingly, and by this operation, the battery's second terminal makes 
electrical contact with the case's second section only when the case's two 
sections are angularly rotated relative to one another to greater than the 
predetermined second degree. Further by this operation, the electrical 
circuit is completed, and the light bulb is energized so as to emit light, 
only when the case's two sections are angularly rotated relative to one 
another to greater than the predetermined first degree or the 
predetermined second degree, whichever is largest. Typically the 
predetermined first and second degrees are equal to each other within 
90.degree. of angular rotation, and are more typically equal to each other 
within 10.degree.. Each of the predetermined first and second degrees is 
typically equal to approximately 0 360, or one complete turn, of angular 
rotation between the two sections of the tubular flashlight case. 
In accordance with the second aspect of the present invention, a removable 
and replaceable shock-resistance light bulb assembly for a flashlight is 
provided. The assembly includes a generally cylindrical miniature light 
bulb having a light-emitting filament and a base from which two electrical 
wire leads extend. 
A generally cylindrical first member of an electrically-insulating 
shock-absorbing material, typically thermoplastic, encapsulates the light 
bulb within an interior cavity. The first member holds the light bulb with 
its filament exposed, typically between a number, normally four, 
arcuately-arrayed elongate "fingers". The first member presents a 
circumferential flange at one of its cylindrical ends. One of the two wire 
leads of the light bulb is routed substantially centrally axially through 
the body of cylindrical member to a first exterior position substantially 
at a geometric center of that same cylindrical end of the member which 
presents the flange. This wire routing permits that a first external 
electrical contact may subsequently be made at this first position. 
The remaining one of the two wire leads of the light bulb is routed 
substantially radially through the body of cylindrical member to an second 
exterior position substantially along an exterior annulus of the flange 
and on a side of the flange that is opposite to that side at which the 
first electrical contact may be made. This wire routing permits that a 
second electrical contact may subsequently be made at this second 
position. 
A generally cylindrical second member of an electrically-conducting rigid 
and strong material, typically machined aluminum, slides over the first 
member until it permanently sleeves the first member in a position 
abutting the first member's flange. In this position the second member 
securely holds the first member with the filament of the miniature light 
bulb exposed in a first axial direction. In this first direction the 
second member normally presents a precision, polished, paraboloidal 
reflective surface having the light bulb's spatially-minute filament at 
its focus. Because of the principles of optics, a very sharp, clean, light 
beam may subsequently be emitted. The second member also makes an 
electrical connection to a wire lead of the light bulb at the second 
position. 
The light bulb that is held within the first member which is, in turn, held 
within the second member constitute, collectively and in combination, a 
replaceable assembly for use in a flashlight. The assembly is easily held 
and manipulated with the human hand and fingers. When emplaced in a 
flashlight of complimentary configuration the assembly provides a new bulb 
securely isolated against shock and precision-positioned relative to a 
new, shiny and untarnished, reflector surface. Massive metal surfaces of 
the second member permit excellent and reliable electrical contact to be 
made to the replaceable assembly, and to the miniature bulb held therein, 
even though the wire leads of the bulb itself (now encapsulated) are 
relatively small and delicate. 
Both the redundant switches, and the shock-mounted light bulb assembly, of 
the present invention may be individually incorporated in flashlights of 
various types used for diverse purposes. In one particular, and preferred, 
usage, a flashlight in accordance with the present invention is provided 
with a strong, but lightweight, machined aluminum case having a 
screw-thread fitting at the exterior of its butt end. The flashlight may 
be securely screwed onto a complimentary fitting at the tip of a 
collapsible police baton, such as the batons taught within the 
aforementioned U.S. Pat. Nos. 4,752,072 issued Jun. 21, 1988, and 
5,110,375 issued May 5, 1992. The flashlight so constructed and mounted is 
substantially impervious to damage or failure during the most extreme 
conditions of use and abuse, specifically including use in striking as 
part of a baton. Yet the flashlight may be readily be field stripped, and 
reassembled, by use of only the hands and fingers under adverse conditions 
of weather and/or darkness. 
These and other aspects and attributes of the present invention will become 
increasingly clear upon reference to the following drawings and 
accompanying specification.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of a flashlight in accordance with the present 
invention is diagrammatically illustrated in FIG. 1. A detail view of the 
preferred construction of the shock-mounted bulb assembly of the 
flashlight is shown in FIG. 2, with a critical plastic component of that 
assembly further shown in FIG. 3. The new on/off switch of the flashlight 
is shown in detail view in FIGS. 4a-4c. 
The flashlight 1 may optionally be mounted to the tip of a baton 2 
(partial) which is shown in dashed line for not being part of the present 
invention. If so mounted, it is preferably by engagement of female screw 
threads 1111 at the exterior base of the battery-end section 111 of the 
tubular flashlight case 11 with complimentary male threads 21 upon the tip 
of baton 2 (partial) . If the flashlight 1 is not so mounted then a plug 
(not shown) with male threads may be mounted to the same female screw 
threads 1111 at the exterior base of the battery-end section 111 of the 
tubular flashlight case 11. Dependent upon the depth of the threads of 
such a plug (not shown) relative to threads 1111 a small cavity, or void, 
that is useful for storage of identification tags or other small items may 
be created between the plug and the base of the battery-end section 111 of 
the tubular flashlight case 11. 
The battery-end section 111 of the tubular flashlight case 11 houses a 
battery 4 (shown in phantom line for not being part of the present 
invention). The battery 4 is preferably a 3 v.d.c. lithium battery, such 
as DURACELL.RTM.XL.TM. (trademarks of DURACELL, Inc.) type DL2/3A 
available from Duracell, Inc., Bethel, Conn. 06801. 
A light bulb-end section 112 of the tubular flashlight case 11 contains a 
light bulb assembly 12 (shown in greater detail in FIG. 2). The 
battery-end section 111 screws to the light bulb-end section 112, normally 
(but not invariably) by engagement of male threads 1112 upon the former 
section with the female threads 1121 upon the later section. An O-ring 
gasket 13 is preferably fitted within a circumferential groove, or 
channel, 1113 of the battery-end section 111. This O-ring gasket 13 serves 
to seal the battery-end section 111 watertight to the light bulb-end 
section 112 when they are screwed together. 
The battery-end section 111 is metal, typically aluminum, and is normally 
fabricated by machining. It presents an anodized finish, typically black 
in color, everywhere upon its interior and exterior surfaces save for two 
locations, only. The interior base 1114 of the butt end, and the annular 
surface 1115, are exposed native metal. The anodized surfaces are 
electrically insulating whereas the exposed native metal surfaces are 
electrically conducting, as is the battery-end section 111 itself. 
The battery 4 within the battery-end section 111 is urged in the direction 
of light bulb-end section 112. In accordance with a first aspect of the 
present invention--the consequences of which will be further explained 
later--this transpires by action of an assembly 14 consisting of a spring 
141 and an insulating washer 142. For the purposes of the present 
invention it is necessary to understand that this assembly 14 is 
electrically non-conductive between its contacts to the terminal of the 
battery 4, and the native metal interior base 1114 of the butt end of the 
battery-end section 111. Such force biasing without electrical conduction 
could be alternatively obtained, for example, by use of an electrically 
non-conductive spring,,such as one made of plastic. 
Meanwhile, another, further, component exists within the battery-end 
section 111 in the small space between the battery 4 and the native metal 
interior base 1114. This component is normally an electrically-conductive 
metal spring 15. The spring 15 is affixed to, and maintained in electrical 
conductivity with, the native metal interior base 1114--normally by action 
of the spring assembly 14 which sits on top of the spring 15. Importantly 
to the present invention, the spring 15 is shorter in length than the 
spring 141 of spring assembly 14, meaning that its normal extension is 
less than the extension of the spring 141 of the assembly 14. Also 
importantly to the present invention, the spring 14 does not contact any 
electrically conductive portion of the assembly 14 (e.g., the spring 141 
of the assembly 14), normally because the exterior diameter of the coil of 
spring 15 is smaller than the interior diameter of the coil of spring 141. 
It should be understood that the spring 15 is not used for imparting 
positional biasing forces to battery 4. The spring 14 could have been, 
alternatively, a mere pylon of metal, or a stud, or an erect pin. The use 
of the spring 14 provides a useful wiping force during electrical contact 
of the spring with the battery 4, in a manner and under circumstances to 
be explained. 
The light bulb-end section 112, normally also of machined aluminum metal, 
is completely anodized, typically to a black color, everywhere upon its 
interior and exterior surfaces. The light bulb-end section 112 
semi-permanently compressively mounts and retains a lens 16, normally made 
of scratch-resistance hard plastic, in a channel 1122 that is slightly 
recessed from the tip of the light bulb-end section 112 of the case 11. 
The case 11 is rendered water- and gas-tight at the location of lens 16 
and channel 1112 by O-ring 17. The light bulb assembly 12 is rendered 
water- and gas-tight, and is stabilized with a modest degree of elasticity 
and shock absorption, in its location within the light bulb-end section 
112 by the O-ring 124. 
The light bulb assembly 12 my be observed in greatest detail in FIG. 2. A 
miniature light bulb 121 is permanently mounted within the assembly 12. It 
is so mounted by the generally cylindrical first member 122. This first 
member 122 is made of an electrically-insulating shock-absorbing material, 
typically thermoplastic. It holds the light bulb 121 with its filament 
1211 exposed to the exterior of assembly 12, and through the lens 16 to 
the exterior of case 11 and flashlight 1 (all shown in FIG. 1). The 
holding is effected between a number, normally four, arcuately-arrayed 
elongate "fingers" 1221-1224 that are best seen in FIG. 3a. 
The first member 122 also has a circumferential flange 1225. Wire lead 1212 
of the light bulb 121 is routed substantially centrally axially through 
the body of first member 122 to the illustrated first exterior position 
substantially at a geometric center of the cylindrical end of the member 
122. The remaining wire lead 1213 of two such from the light bulb 121 is 
routed substantially radially between any two of the fingers 1221-1224 and 
through the body of cylindrical first member 122 to the illustrated 
exterior position substantially along an exterior annulus of the 
circumferential flange 1225. This location is, of course, on a side of the 
flange 1225 that is opposite to that side whereat appears the wire lead 
1212. 
Continuing in FIG. 2, a generally cylindrical second member 123 slides over 
the first member 122 until it sleeves the first member 122 in a position 
abutting the flange 1223. The second member 123 is necessarily made of an 
electrically-conducting material, and is preferably made of a material 
that is also rigid and strong, more preferably machined aluminum. In its 
mounted position the second member 123 securely holds the first member 122 
with the filament 1211 of the miniature light bulb 121 exposed in a first 
axial direction. The second member 123 presents a precision, polished, and 
typically spheroidal or paraboloidal reflective surface 1231 in this 
direction. The spatially-minute filament 1211 of the light bulb 121 is at 
the focus of this paraboloid. Because of the principles of optics, light 
emissions from the filament 1211 of the light bulb 121 are focused to a 
very sharp, clean, collimated light beam precisely in the axial direction. 
The second member 123 makes an electrical connection to the wire lead 1213 
of the light bulb 121 at the position of its flange 1225. The second 
member 123 is electrically insulated by the electrically non-conducting 
first member 122 from the other wire lead 1212 of the light bulb 121. 
However, in order to facilitate that other things (namely the battery 4, 
as hereinafter explained) should ultimately make electrical contact with 
the wire lead 1212 of the light bulb 121, a small, headed, 
electrically-conductive pin 125, substantially in the shape of a rivet, is 
pressured or otherwise fitted within an axial cavity of complimentary size 
and shape within the first member 122, and against the wire lead 1212. 
The first member 122, which is important to realizing the shock-absorbing 
aspect of the present invention, is further shown in detail end view in 
FIG. 3a, and in detail cross-sectional view in FIG. 3b. The four support 
fingers 1121-1124 are visible in FIG. 3a. Dimension A in FIG. 3b is 
typically 0.305 inches, whereas dimension B is typically 0.280 inches. 
Accordingly, the fingers 1221-1224 of the first member are very slightly 
separated from the encapsulating second member 123 (shown in FIG. 2) and 
provide thereby relief from high G shock forces. Dimensions C-H shown in 
FIG. 3b are typically respectively 0.192", 0.130", 0.25", 0.005", 0.100" 
and 0.675". 
The second on/off switch--in addition to the switching provided between the 
surface 1105 and the light bulb assembly 12/light bulb-end case section 
112 (shown in FIG. 1) in a manner to be explained--of the present 
invention is shown in its two sub-assemblies in FIGS. 4a and 4b, and 
assembled in FIG. 4c. The electrically non-conducting member 14 of a 
second on/off switch of the flashlight in accordance with the present 
invention is shown in side view, partially in cut-away, within FIG. 4a. 
The member 14 typically consists of an electrically-conductive, metal, 
spring 14 and an insulating washer 142. It must act to provide expansion 
force, but it must not be electrically conducting from one end to the 
other. Obviously, alternative constructions such as springs of plastic 
would satisfy these criteria. 
The electrically conducting member 15 of the second on/off switch of the 
flashlight in accordance with the present invention is shown in side view 
in FIG. 4b. Note that its elongate extent is not so great as is the 
electrically non-conducting member shown in FIG. 4a. 
A side view of the electrically non-conducting member 14 previously seen in 
FIG. 4a, assembled to the electrically conducting member previously seen 
in FIG. 4b to form the complete second on/off switch of the flashlight in 
accordance with the present invention is seen in FIG. 4c. 
Returning to FIG. 1, part of the operation of a flashlight 1 in accordance 
the present invention is conventional insofar as the action of the 
assembly 141 serves to push the battery 4 (both assembly and battery which 
are within the battery-end section 111) in the direction of light bulb-end 
section 112. In FIG. 1 the tubular case sections 111, 112 of the 
flashlight 1 are unscrewed several turns, and to such a great extent that 
the battery 4 is not in contact with the electrically-conductive pin 124. 
Normally, and under more tightly screwed, operational, conditions the case 
sections 111, 112 are sufficiently screwed together so that the force 
biasing action of the assembly 14 against the battery 4 serves to keep the 
battery 4 in constant contact with the electrically-conductive pin 125, 
and the wire lead 1212 of the light bulb 121, regardless of whether the 
battery-end section 111 is screwed completely into, or is backed off a 
turn or so, from the light bulb-end section 112. 
In accordance with a first aspect of the present invention, the extent to 
which the battery-end section 111 is screwed into the light bulb-end 
section 112, makes and breaks two separate electrical switches. The more 
conventional of these switches may be recognized as the mating contact 
between the native metal annular surface 1115 of the battery-end section 
111 and the complimentary native metal surface of the second member 123 of 
the light bulb assembly 12. These surfaces are, of course, normally urged 
to separation by the force of force biasing assembly 14 (i.e., by the 
contained spring 141 of this assembly) acting--through the physical body 
of battery 4, and the headed pin 125 and first member 122 of light bulb 
assembly 12--between the battery-end section 111 and the second member 
123. These surfaces are, of course, forced into electrical contact only 
when the battery-end section 111 is screwed into the light bulb-end 
section 112 to a sufficient extent, normally about 1.0 turn (360.degree.) 
from mechanical tight lock. 
The second electrical switch is likewise made, and broken, by the extent to 
which the battery-end section 111 is screwed into the light bulb-end 
section 112. This switch is between the spring 15 (and all that it 
continually electrically contacts including the battery-end section 111) 
and the opposed terminal of the battery 4. Only when the battery-end 
section 111 is screwed into the light bulb-end section 112 (against the 
biasing force of the biasing assembly 14) to a predetermined extent will 
the normal gap between the spring 15 and the opposed terminal of battery 4 
be closed, and electrical continuity made. 
The two electrical switches are in electrical series. Both must be made in 
order to energize the light bulb 121 from the battery 4. Conversely, 
either switch can be broken in order to turn the flashlight 1 off. One 
utility of having dual, series-connected, electrical switches may be 
assessed if it is considered what will electrically transpire if, over 
time and after wear, the insulating anodizing is worn from the threaded 
surfaces of the battery-end section 111 and the light bulb-end section 
112. An electrical path to the light bulb 121 through these surfaces would 
prevent that the flashlight should be turned off save for the action of 
the second, redundant, switch enabled by assembly 14 and spring 15. 
The two electrical switches both operate by the angular rotation of, and 
the screwed engagement of, the battery-end section 111 and light bulb-end 
section 112. The point, and the relative angular movement, at which each 
of the two switches both engages and disengages could be independent, and 
separately predetermined for each switch. In accordance with the present 
invention, both switches are designed to turn on, and to turn off, at the 
same degree of angular rotation, and screwed engagement, of the 
battery-end section 111 and light bulb-end section 112. The consumer/user 
of the flashlight 1 need not be concerned with the workings of the 
switches. 
In accordance with the preceding explanation, alternative constructions, 
and modifications, of the flashlight in accordance with the present 
invention will suggest themselves to a practitioner of the 
electromechanical design arts. For example, the concept of low-cost, 
low-mass, high-reliability redundant switching in a device so elementary 
as a twist-on/twist-off flashlight having been put forward in this 
specification, it is an easy matter to design switches, and circuit paths, 
that are redundant for turning the flashlight on (as opposed to off, as in 
the present invention). 
For example, alternative constructions of a modular replaceable shock-mount 
assembly for a miniature flashlight bulb might use a suspension, or an 
elastomeric material, shock mounting for the bulb. 
For example, the relative motion serving to compress the new second on/off 
switch need not transpire solely by rotation between the sections 111, 112 
of case 11. Instead, a plunger, a mechanical rocker, or other mechanism 
could be located behind the butt end of the case section 111, and in the 
location of the baton 2 (partial) (shown in FIG. 1). Finger-activated 
depression of such a mechanism would operate to move a rod, or plunger, 
through an axial bore located in the base of case section 111, and so as 
to force the spring assembly towards the battery 4. In such a manner still 
another manually activated on/off switch would be created. A flashlight 1 
so expanded, and extended, by still further application of the principles 
of the present invention would have two complete, and redundant, means of 
manual actuation. Even if the case 11 became so distorted and damaged so 
that its sections 111, 112 would no longer screw together, a new switch at 
the butt end of the case 11 could still move the spring assembly 14, and 
spring 15, so as to selectively energize the light bulb 121. 
According to these and other alterations and adaptations, the present 
invention should be interpreted broadly, and in accordance with the 
following claims only, and not solely in accordance with that particular 
embodiment within which the invention has been taught.