Abstract:
An electrical switch comprising a helical spring, progressively compressed onto concentric annular contacts, provides a mechanism for operating a portable light or other devices, and for engaging multiple modes of operation of said device(s), for example a portable electronic flashlight.

Description:
FIELD OF THE INVENTION 
   This invention relates to electrical switches, and more particularly to switches controlling the operation of electronic flashlights. 
   DESCRIPTION OF THE RELATED ART 
   Contemporary small, portable lights or flashlights most commonly use one spring and one fixed contact for connections to the cathode and anode of a dry cell battery, respectively. The spring in these units commonly presses into and connects with the cathode of the dry cell battery, and said spring&#39;s spring force is used to press the dry cell battery&#39;s anode into a second, fixed contact, inferior to the bulb assembly. Metallic straps or wires are used to connect these contacts sequentially to the flashlight&#39;s bulb and power switch, respectively providing means for conveying electrical power to the flashlight&#39;s bulb, and for interrupting that power to turn the light on and off. In the case of flashlights with metallic bodies the body itself may serve as part of the circuit, replacing one of the conductors. Examples of this scheme are ubiquitous in flashlights made by Ray-O-Vac, Duracell, Garrity, Mag Instruments, among others. 
   Switches commonly used in the above scheme include sliding switches, such as a thumb-activated slide mechanism on the outside of the flashlight body, and pushbutton switches, either mounted in the body of the flashlight, or at the tailcap. All of these switches require penetration of the flashlight body, leaving gaps and openings through which water can enter and ruin the flashlight. Slide switches in particular are vulnerable to leakage. Further, while rubber domes with round rubber gasket skirts have been developed to cover pushbutton switches, providing some measure of water resistance, the result falls short of full water-tightness. 
   Other flashlights of contemporary design, such as the Energizer Waterproof flashlight model WP250WB-E, comprising a plastic body and a twist-on head, incorporate a “twist-on” switch. Said switch is operated by rotating the flashlight&#39;s head, clockwise turning the flashlight on, and counterclockwise to turn the flashlight off. Such switches have the great advantage of being entirely inside the flashlight&#39;s body, with water-tightness ensured by o-ring seals that seal the flashlight&#39;s head to its body. Water-tightness can be achieved at depths exceeding 100 meters of water. This switch comprises a rigidly mounted contact in the head assembly which, when the head is operated, is pressed into contact with the anode of a dry cell installed beneath it. Said switch, while effective in a conventional incandescent flashlight, does not provide means for controlling a multiplicity of modes for a more flexible, more capable electronic flashlight. 
   SUMMARY OF THE INVENTION 
   The advent of light emitting diodes (LEDs) has resulted in a new array of lighting products with capabilities unavailable in older, incandescent-based products. The instant invention discloses an electrical switch suitable for controlling the operation of a more advanced flashlight, especially one with multiple modes. 
   The preferred embodiment teaches how a spring—such as a helical spring fashioned of steel, stainless steel, copper alloy, brass, or other suitable metal or alloy, with or without chromium or other protective plating—can be combined with a suitable array of contacts to produce a multi-position shorting switch that is inexpensive, durable, and reliable. Said switch can be readily fabricated on one side of a printed circuit board, allowing it to operate circuitry assembled on the opposite side of same. Furthermore, said switch can be contained within the protective environment of the flashlight housing, facilitating construction of waterproof flashlights. 
   Additionally, the instant invention provides for contacting an electrode of a dry cell, thus combining an additional function without additional cost, reducing parts count, and reducing the number of interconnection points in the flashlight&#39;s electrical circuit. Reliability is accordingly increased. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts a cut-away view of the invention. 
       FIG. 2  is a top-view of the contact assembly. 
       FIGS. 3   a–c  are cut-away views of the invention in various stages of operation. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  depicts one preferred embodiment of the invention. A helical spring  101  made of a suitable electrically conductive material such as (but not limited to) steel, stainless steel, copper alloy, brass, or other suitable metal or alloy, with or without chromium or other protective plating, possessing coils  102 – 108 , is positioned over concentric annular contacts  201 – 203 . Said contacts  201 – 203  may be conductors laminated to a printed circuit board.  109 . Connections  111  connect contacts  201 – 203  to circuitry  110 . 
     FIG. 2  is a top-view of contacts  201 – 203 , showing said contacts as well as insulating gaps  204 – 205 . Gaps  204 – 205  serve to electrically isolate contacts  201 – 203  from each other until such time as the invention is activated. Contacts  201 – 203  may be supported by an insulating substrate, such as a fiberglass printed circuit board. Depiction of connections from contacts  201 – 203  to external circuitry has been omitted for clarity, but should be obvious to those skilled in the art. 
   OPERATION OF THE INVENTION 
     FIG. 3   a  depicts a first state in which dry cell  301  has been positioned so that its anode  302  has just begun to touch coil  105  of spring  101 . Spring  101 &#39;s coils  102 – 108  are therefore only slightly compressed, none sufficiently to be advanced into contacts  202  or  203 . In this first state, spring  101  is in electrical and mechanical contact with contact  201 . This creates a first circuit, connecting battery anode  302  with contact  201  via spring  101 . In this first state contacts  202  and  203  are open circuits. 
     FIG. 3   b  depicts a second state in which dry cell  301  is applying an additional compressing force to spring  101 , as would happen, for example, if the entire switch assembly comprising  101 – 108  and  201 – 205  were squeezed partially together with dry cell  301 . Said compression of spring  101  forces coils  103  and  107  into contact with contact  202 , creating a second circuit. Said second circuit electrically connects battery anode  302  with contacts  201 – 202  via spring  101 . 
     FIG. 3   c  depicts a third condition in which dry cell  301  has advanced sufficient distance to fully compress spring  101 . Coils  103  and  107  are pressed into mechanical and electrical contact with contact  202 , and coils  104 – 106  are forced into contact with contact  203 , creating a third state. In this third state spring  101  electrically connects battery anode  302  to all of the contacts  201 – 203 . 
   In brief, this preferred embodiment of the invention yields a single-pole, three-position shorting switch that can simultaneously provide connection to a battery. This switch can be used wherever a shorting single-pole multiple-position switch is desired, such as for controlling the brightness level or other operating mode of an electronic flashlight. 
   Although one preferred embodiment of the invention has been described, numerous embodiments in the spirit of the present invention will be apparent to those skilled in the art. For example, more or fewer than the three contacts  201 – 203  depicted in  FIG. 2  may be used, adapting the invention to circumstances needing more or fewer switch positions. If an initial open circuit condition is desired, annular contact  201  may be omitted, or the space between spring  101  and dry cell  301  may be increased until the two do not initially touch.  FIG. 3  depicts the invention being operated by the anode  302  of a dry cell  301 , however the invention can be operated equally well by either electrode of a dry cell, or by an external mechanical plunger if desired. A helical spring  101  has been shown and is preferred for cost, simplicity, and performance, but a cantilevered lever arm or a metallic “snap” dome may be substituted to perform the same function. The contacts  201 – 203  need not be of annular configuration, but may take other shapes, such as concentric rings with finger-like projections that interleave in gaps  204 – 205  with similar projections from the opposing contact, pie-shaped wedges, among other shapes. Lastly, contacts  201 – 203  need not be flat, but can contained raised structures such as solder bumps, or other conductive bumps or contact areas designed to raise the contact force, lowering contact resistance. Bare metal “jumper” wires, positioned at various radii and oriented 90 degrees to spring coils  201 – 203  are another such alternative contact structure. All of these alternatives flow from and are anticipated in the practice of the instant invention.