Abstract:
A switch as for a flashlight selectively connects, for example, a solid state light source and a battery in the flashlight in circuit for causing the solid state light source to produce light. The switch comprises a pushbutton and a metal contact having a circular periphery that selectively contacts a housing, and a spring. Pressing the pushbutton moves the pushbutton and the metal contact to contact the housing. The metal contact may be a ferrule having a cylindrical portion centered with respect to the housing end and a circular flange providing the circular periphery. The switch may be disposed in a tail cap attached to a flashlight housing at a cylindrical end thereof.

Description:
This application is a division of co-pending U.S. patent application Ser. No. 09/511,876 filed Feb. 25, 2000, and hereby claims the priority thereof. 
    
    
     The present invention relates to a switch, and in particular to a switch for a flashlight. 
     Flashlights are available in a wide variety of shapes and sizes, and tailored to a particular use or situation. However, two desires that continue to indicate the need for improved flashlights include the desire for small flashlights and longer useful life. For example, there is a desire for a flashlight that is of a size and shape to conveniently fit in a pocket, e.g., a shirt pocket. In addition, there is a desire for a flashlight that has a bright beam and that operates for a long time before needing to replace or recharge the battery. Also, consumers also want such flashlights to be durable and available at a reasonable cost. 
     Prior art pocket lights such as a typical pen-shaped light typically are about 1.3 to 2 cm in diameter and are quite heavy, principally due to the size and weight of the type AA (about 1.4 cm diameter) or type AAA (about 1 cm diameter) batteries therein. It would be desirable to have a flashlight of about 1 cm or less in diameter, which is closer to the diameter of typical pens and pencils also kept in a person&#39;s pocket. A further advantage of a smaller-diameter flashlight is the ability to shine the light into small spaces. 
     The desire for a small-diameter flashlight makes the inclusion of complex internal current-carrying conductors undesirable because they tend to increase the diameter of the light, as well as adding cost thereto, i.e. cost for material, cost for fabrication of the internal parts, and added cost for assembly of the flashlight. 
     Prior art flashlights typically employ filament-type lamps that have a filament that is electrically heated to glow to produce light, wherein the filament is suspended between supports. Typical filaments tend to be fragile, and often more so when they are heated to glowing. As a filament is used, the filament material may thin or become brittle, thereby increasing its susceptibility to breakage. Even high-light-output lamps such as halogen and xenon lamps employ a heated filament, albeit a more efficient light producer than is a conventional incandescent lamp filament. A solid-state light source, such as a light-emitting diode (LED), for example, does not have a heated filament and so is not subject to the disadvantages associated with lamp filaments, and such LEDs are now available with sufficiently high light output as to be suitable for the light source for a flashlight. 
     A simple switch is desired for the foregoing and other flashlights, and for utilization in other apparatus. Accordingly, there is a need for switch that is simple and can be made at a reasonable cost. 
     To this end, the switch of the present invention comprises a hollow cap engaging the end of a housing, a pushbutton in the cap and movable axially therein, and a metal electrical contact having a circular periphery and a central opening. The metal electrical contact engages the pushbutton and is movable axially in the cap to selectively contact the end of the housing for making selective electrical contact therewith. A coil spring is disposed axially for urging the metal electrical contact away from the housing in the cylindrical cap. 
     According to another aspect of the invention, a switch assembly comprises a pushbutton having an outward flange and a body portion of lesser diameter than the flange thereof, wherein the pushbutton is electrically insulating, and a metal electrical contact having an outward circular contact flange and having a central opening therethrough. The metal electrical contact engages the pushbutton, and an electrically conductive coil spring is disposed axially with respect to the pushbutton and extends into the central opening of the metal electrical contact for electrically contacting the metal electrical contact. The coil spring is for urging the metal electrical contact and the pushbutton in the same direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The detailed description of the preferred embodiments of the present invention will be more easily and better understood when read in conjunction with the FIGURES of the Drawing which include: 
     FIG. 1 is a side view of an exemplary embodiment of a flashlight in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of the flashlight of FIG. 1; 
     FIG. 3 is a side cross-sectional view of the flashlight of FIG. 1; and 
     FIG. 4 is an enlarged side cross-sectional view of a portion of the barrel of the flashlight of FIG.  1 . 
    
    
     In the Drawing, where an element or feature is shown in more than one drawing figure, the same alphanumeric designation is used to designate such element or feature in each figure, and where a closely related or modified element is shown in a figure, the same alphanumerical designation primed may be used to designate the modified element or feature. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a side view of an exemplary embodiment of a flashlight  10  in accordance with the present invention. Flashlight  10  has a forward or head end  12  at which light is produced by a light source assembly  100  including a solid-state light source  110  such as an LED, and a rearward or tail end  14  at which is a tail switch assembly  200  including a pushbutton  210 . Hollow cylindrical housing  20  of flashlight  10  has an elongated hollow cylindrical portion  22  and a hollow reduced inner diameter portion  24 , for example, a tapered portion  24 , proximate head end  12 . Housing  20  is formed into a generally rounded forward end  26  at head end  12  and has a circular hole therein through which solid state light source  110  of light source assembly  100  projects in a forward direction. Cylindrical tail cap  40  overlies cylindrical housing  20  at the tail end  14  of flashlight  10  and has a circular hole  42  therein through which pushbutton  210  of tail switch assembly  200  projects in a rearward direction. Light source  100  is turned on by either depressing pushbutton  210  or by rotating tail cap  40  further onto housing  20 . 
     FIG. 2 is an exploded perspective view of the flashlight  10  of FIG. 1 illustrating the external and internal components thereof Hollow cylindrical housing  20  includes an elongated hollow cylindrical portion  22  and a hollow reduced inner diameter portion  24 , for example, a tapered portion  24 , proximate rounded forward end  26  thereof in which is formed circular hole  28  through which the light-emitting lens of light source  110  projects. Tubular housing  20  includes external threads  30  at the rearward end thereof for engaging the internal threads (not visible in FIG. 2) on the inner surface of tail cap  40 . Housing  20  has a circumferential groove  32  forward of threads  30  for receiving a resilient O-ring  38  therein that provides a water-resistant seal between housing  20  and tail cap  40 . 
     Internal components that slip inside the hollow cylindrical housing  20  include light source assembly  100  and batteries  60 . Light source assembly  100  includes solid state light source  110  mounted in cylindrical base  120  with its electrical lead  114  in a longitudinal slot therein. Resilient O-ring  116  fits over light source  110  to provide a water-resistant seal between light source  110  and housing  20  when light source assembly is installed forward within housing  20  with O-ring  116  bearing against the internal forward surface thereof proximate circular hole  28 . Batteries  60  each include a positive terminal  62  and a negative terminal  64  and are connected in series to provide a source of electrical energy for energizing light source  110  to cause it to produce light. Typically, two batteries  60  (as illustrated) or three batteries  60  are employed, although a greater or lesser number could be employed by appropriately lengthening or shortening the length of housing  20 . Preferably, batteries  60  are of the type AAAA alkaline cells which provide a voltage of about 1.2-1.5 volts and have a diameter of about 0.8 cm or less. As a result, flashlight  10  has an outer diameter of only about 1 cm (about 0.38 inch), and is 12.6 cm (about 4.95 inches) long for a two-battery flashlight and 16.8 cm (about 6.6 inches) long for a three-battery flashlight, and operates for about 10 hours or more on a set of batteries. 
     The small outer diameter of flashlight  10  advantageously permits flashlight  10  to be “pocket-sized” in that it is of a size that permits it to be carried in a pocket or pouch, if so desired, although it need not be. 
     At the rearward or tail end  14  of flashlight  10 , tail switch assembly fits inside the central cavity of tail cap  40  with circular pushbutton  210  of tail switch assembly  200  projecting through circular hole  42  in the rearward end thereof. Resilient O-ring  214  on pushbutton  210  provides a water-resistant seal between pushbutton  210  and tail cap  40  when pushbutton  210  is installed therein with O-ring  214  bearing against the interior surface of tail cap  40  proximate circular hole  42  therein. 
     Selective electrical connection between negative terminal  64  of rearward battery  60  and the rearward end metal housing  20  is made via outwardly extending circular metal flange  222  which is electrically connected to coil spring  226 . When push button  210  is depressed or when tail cap  40  is screwed further onto threads  30  of housing  20  moving tail switch assembly  200  forward relative to housing  20 , metal flange  222  comes into electrical contact with the rearward annular surface of cylindrical housing  20  thereby to complete an electrical circuit including batteries  60  and light source  110 , to the end of applying electrical potential to solid state light source  110  to cause it to emit light. 
     FIG. 3 is a side cross-sectional view of the flashlight  10  of FIG. 1 showing the relative positions of the external and internal components thereof when tail cap  40  is screwed onto threads  30  of housing  20  sufficiently to cause metal flange  222  to contact the rear end of housing  20 , thereby to energize light source  110  to produce light as described above. Switch assembly  200  is free to move axially forward and rearward within housing  20  and tail cap  40 , and does so under the urging of coil spring  226  and pressure applied to pushbutton  210 . Unscrewing tail cap  40  moves tail cap  40  rearward and allows switch assembly  200  therein to also move rearward under the urging of spring  226 , thereby breaking contact between metal flange  222  and the rear end of housing  20  and breaking the electrical circuit including batteries  60  and LED light source  110 , thereby to de-energize light source  110  to stop the producing of light. Momentary switching (or blinking) action obtains from depressing/releasing pushbutton  210  when tail cap  40  is unscrewed slightly from the position illustrated in FIG.  3  and continuous on/off operation obtains by screwing tail cap  40  onto/away from housing  20  sufficiently to cause light assembly  110  to produce and not produce light. 
     Coil spring  226  urges batteries  60  forward causing their respective positive terminals  62  and negative terminals  64  to come into electrical contact and complete an electrical circuit between metal coil spring  226  and electrical lead  134  of light source assembly  100 . In assembling flashlight  10 , light source assembly  100  is inserted into housing  20  and is pushed forward causing electrical lead  114  thereof to come into physical and electrical contact with the interior surface of the wall of metal housing  20 , e.g., by abutting housing  20  at shoulder  27 . Light source assembly  100  is inserted sufficiently far forward to cause O-ring  116  to provide a seat between light source  110  and the interior surface of housing  20  proximate circular hole  28  therethrough. Light source assembly  100  is preferably a press fit into the tapered portion  24  of housing  20  owing to the contact of lead  114  and cylindrical body  120  with the interior surface of tapered portion  24 . 
     Light source assembly  100  includes a solid state light source  110 , preferably a light-emitting diode (LED). LEDs are available to emit light of one of a variety of colors, e.g., white, red, blue, amber, or green, and have extremely long expected lifetimes, e.g., 100,000 hours. Light source assembly  100  includes an insulating cylindrical body  120  having a central cavity  122  therein and a longitudinal slot  124  axially along one external surface thereof. LED light source  110  mounts into cylindrical body  120  with one electrical lead  114  thereof lying in slot  124  so as to come into physical and electrical contact with the interior surface of tapered portion  24  of cylindrical housing  20  and with the other electrical lead  112  thereof connected to lead  132  of electrical device  130  within central cavity  122  of cylindrical body  120 . The other electrical lead  134  of electrical device  130  projects rearwardly out of the central cavity  122  of cylindrical body  120  to come into electrical contact with the positive terminal  62  of forward battery  60 , thereby to complete an electrical circuit between battery  60  and metal housing  20  through LED light source  110 . Electrical body  120  is preferably a rigid dielectric material such as a moldable plastic or ceramic, such as a glass-filled PBT plastic. 
     Electrical device  130  is preferably an electrical resistor with one of its leads  134  contacting battery  60  and the other of its leads  132  connected to lead  112  of LED light source  110  to limit the current that flows therethrough, thereby to extend the life of LED light source  110  and of batteries  60 . Resistor  130  is preferably a carbon film resistor, and other types of resistors can be utilized. If a reverse potential were to be applied to LED light source  10 , as could occur if batteries  60  were installed backwards, the diode action of LED light source  110  and resistor  130  prevent excess current flow in LED light source  110  that might otherwise cause the light-emitting diode therein to become degraded, damage or burned out. 
     Tail switch assembly  200  is positioned within tail cap  40  at the rearward end  14  of flashlight  10 . Tail switch assembly  200  includes a generally cylindrical pushbutton  210  of insulating plastic that includes a rearward cylindrical section that projects through hole  42  of tail cap  40  and has a circumferential groove  212  in which resilient O-ring  214  resides to provide a water resistant seal between pushbutton  210  and tail cap  40  proximate hole  42  therein. Tail cap  40  includes a cylindrical skirt  48  extending forwardly from internal threads  44  therein and extending along housing  20 . Tail cap skirt  48  provides an inner surface for sealing tail cap  40  against O-ring  38 , and also provides a greater length to tail cap  40  thereby making it easier to grip for rotating tail cap  40  relative to housing  20  to turn flashlight  10  on and off. 
     Pushbutton  210  also includes a central cylindrical section having a greater diameter than the rearward section thereof to provide an outwardly extending circular flange  216  that engages a corresponding shoulder  46  of tail cap  40  to retain pushbutton  210  captive therein. Forward cylindrical body section  218  of pushbutton  210  is preferably of lesser diameter than the rearward section and circular flange  216  thereof to receive a cylindrical metal ferrule  220  thereon. Metal ferrule  220  receives metal coil spring  226  in the forward cylindrical section thereof and includes circular flange  222  extending radially outward therefrom Radial flange  222  comes into contact with the rearward end of housing  20  when pushbutton  210  is depressed or when tail cap  40  is rotated clockwise with respect to housing  20  to advance axially forward thereon due to the engagement of the external threads  30  on the external surface of housing  20  and the internal threads  44  of tail cap  40 . Insulating plastic cylindrical ferrule  230  surrounds metal ferrule  220  and centers tail switch assembly within the central longitudinal cylindrical cavity of housing  20 . Preferably, metal ferrule  220  is a tight fit over cylindrical body section  218  of pushbutton  210  and plastic ferrule  230  is a tight fit over metal ferrule  220  for holding together with a slight press fit, without need for adhesive or other fastening means. 
     Alternatively, body portion  218 , metal ferrule  220  and insulating ferrule  230  may each be tapered slightly for a snug fit when slipped over each other, and metal ferrule  220  may be split axially so as to more easily be expanded and compressed for assembly over body portion  218  and securing thereon by ferrule  230 . Metal ferrule  220  is preferably brass, but may be copper, aluminum, steel or other formable metal. Coil spring  226  is preferably stainless steel, but may be of steel, beryllium copper or other spring-like metal. 
     Housing  20  and tail cap  40  are metal so as to provide an electrically conductive path along the length of flashlight  10 , and are preferably of aluminum, and more preferably of 6000 series tempered aircraft aluminum Housing  20  and tail cap  40  are preferably coated for aesthetics as well as for preventing oxidation of the aluminum metal, and preferably are coated with a durable material such as an anodized finish, which is available in several attractive colors such as black, silver, gold, red, blue and so forth While an anodized finish is hard and durable, it is not electrically conductive and so, absent the arrangement of the present invention, interferes with completing an electrical circuit including batteries  60  and light source  110  through housing  20 . 
     To the end of providing one or more electrical connections to housing  20 , FIG. 4 is an enlarged side cross-sectional view of a forward portion of housing  20  of the flashlight  10  of FIG.  1 . Housing  20  is preferably formed from a cylindrical aluminum tube or tube stock, such as an extruded cylindrical tube, preferably an aluminum tube having an outer diameter of about 1 cm or less, as follows. An length of aluminum tube is cut to a length slightly longer than the axial length of housing  20  and one end thereof forward of break line  23  is roll formed, preferably cold roll formed, so as to have a slight narrowing taper, thereby forming tapered portion  24  of housing  20  having an inner diameter that is less than the inner diameter of the remainder of housing  20  proximate the forward or head end  12  thereof. A taper angle A of less than about 5° from the longitudinal center axis  21  is desirable. In fact, for an about 1 cm diameter tube, a taper of about 2° is preferred. Housing  20  is further roll formed at the head end  12  of tapered portion  24  to form a rounded forward end  26  having a narrowed-diameter opening therein that is trimmed, such as by drilling or boring, to provide circular hole  28  coaxially with housing centerline  21 . The roll forming of tapered portion  24  and rounded end  26  may be performed in a single operation. Housing  20  is coated with the preferred anodized or other finish, preferably before the forming and subsequent operations. 
     Because the preferred anodized finish is not electrically conductive, it must be removed at locations on housing  20  at which electrical connection is to be made. To this end, the reduced inner diameter tapered forward portion  24  of housing  20  provides a particular advantage, it being noted that the rolling tapers both the outer and inner surfaces of tapered portion  24 . Because the aluminum tube is tapered only at its forward end, the interior diameter of housing  20  is of uniform inner diameter D 1  over its entire length except at tapered portion  24  forward of break line  23  where it has a reduced diameter. Thus, a reamer or boring tool of diameter D 2  greater than the inner diameter of the reduced inner diameter portion  24  and less than the inner diameter D 1  of the remainder of housing  20  will remove the insulating coating only in the reduced inner diameter portion  24  of housing  20  and form a ridge or shoulder  27  at the forward end thereof. A housing  20  so formed may have a cylindrical outer shape or other outer shape, as is desired. The clearance reamer or other boring tool is inserted into the interior of housing  20  from the tail end  14  thereof and through cylindrical portion  22  thereof and includes a cutting head that cuts a bore of diameter D 2  that is less than the inner diameter D 1  of cylindrical portion  22 , and so does not cut within portion  22  and remove the electrically insulating coating therefrom, and may include a non-cutting guide of a diameter greater than D 2 , but less than D 1 , rearward of its cutting head for centering the boring tool substantially coaxially along centerline  21  of housing  20 . 
     As the clearance reamer or boring tool advances forwardly into tapered portion  24 , it cuts a cylindrical bore  25  of diameter D 2  interior to tapered portion  24 , thereby cutting through the non-conductive anodized coating to expose the conductive aluminum metal of housing  20 , to provide a contact area to which electrical lead  114  of light source assembly  100  makes electrical contact when light source assembly  100  is inserted into housing  20  and advanced forwardly therein until light source  110  abuts, i.e. is proximate to, shoulder  27  and extends through hole  28 . The diameter D 2  and length L of bore  25  are selected to provide sufficient exposed aluminum contact surface in bore  25  while leaving sufficient thickness in the forward end of the wall of tapered portion  24  of housing  20 . Typically, housing  20  has an outer diameter of about 0.95 cm, an inner diameter of about 0.80 cm, and bore  25  has a diameter D 2  of about 0.79 cm and a length L of about 0.9-1.0 cm. 
     The rearward end  14  of housing  20  has external threads  30  formed on the outer surface thereof, such as by machining or cold forming, and the anodized finish is removed from rearward end of housing  20 , such as by machining or grinding, so as to expose the metal of housing  20  to provide a location to which circular flange  222  of metal ferrule  220  can make electrical contact. 
     Alternatively, the boring tool utilized to cut bore  25  in tapered portion  24  may also include a second cutting head of lesser diameter located forward of the cutting head that cuts bore  25 , wherein the second more-forward cutting head is utilized to bore hole  28  in a single operation with the cutting of bore  25 . 
     While housing  20  has been described in terms of tapered portion  24  of housing  20  having an interior surface that is tapered so that a reamer or boring tool may be utilized to remove the electrically insulating anodize coating therefrom, any form of housing  20  having a reduced inner diameter portion  24  near the forward end  12  thereof that a reamer or boring tool or other like tool may be utilized to remove the electrically insulating coating therefrom. Thus, a housing having a reduced inner diameter portion  24  is satisfactory irrespective of whether or not the exterior surface of the reduced inner diameter portion  24  of housing  20  is of the same, smaller or larger outer diameter than is the rest of housing  20  and irrespective of whether the shape of the outer surface of reduced inner diameter portion  24  of housing  20  is the same as or different from the shape defined by the inner surface of reduced inner diameter portion  24  thereof. 
     Accordingly, housing  20  may be formed by thin-wall impact extrusion wherein a blank or preform of metal such as aluminum is deep drawn to form a cylindrical housing  20  having a cylindrical interior bore that is of a given diameter except at the forward end thereof at which it has a reduced inner diameter. The reduced inner diameter portion may be a tapered interior shape or may be a smaller diameter cylindrical bore, for example. In impact extrusion, which can be utilized in quickly forming relatively deep closed-ended metal objects such as food and beverage cans and cigar tubes, a blank of material to be extruded is forced into a cavity tool that has a cavity of substantially the same size and shape as the desired outer shape of the extruded object to determine the outer shape thereof. The blank is forced into the cavity of the cavity tool by a core tool that has an outer shape that is substantially the same size and shape as the desired inner surface of the extruded object. The shape and size of the elongated closed-ended tube so formed by impact extrusion is defined by the generally cylindrical gap between the cavity tool and the core tool when the core tool is fully driven into the cavity of the cavity tool, similarly to a mold. The extruded object is removed from the cavity and core tools and is trimmed to the desired length of the extruded object. 
     Housing  20  formed by impact extrusion is removed from the cavity and core tools and the rearward end thereof is cut to the desired length. The resulting extruded hollow tube is then coated with an insulating coating such as an anodize coating. Thus, a reamer or boring tool of diameter greater than the inner diameter of the reduced inner diameter portion  24  and less than the inner diameter of the remainder of housing  20  will remove the insulating coating only in the reduced inner diameter portion  24  of housing  20 , and may include a portion forward of the reamer or boring tool portion for substantially contemporaneously cutting opening  28  in the forward end of housing  20 . A housing  20  so formed by thin wall impact extrusion may have a cylindrical outer shape or other outer shape, as is desired. 
     Alternatively, housing  20  may be formed by boring or drilling an interior bore into a solid piece of material, such as a rod or bar of aluminum or other metal, for example. The drilling or boring of such deep small-diameter holes is usually referred to as “gun boring.” The drilling or boring tool can have a smaller-diameter forward portion and a larger-diameter rearward portion so as to drill or bore a hole having a reduced inner diameter forward portion  24 , which forward portion  24  may be a cylindrical bore or a tapered bore or other reduced inner diameter bore. Housing  20  is then coated with an insulating coating such as an anodize coating. Thus, a reamer or boring tool of diameter greater than the inner diameter of the reduced inner diameter portion  24  and less than the inner diameter of the remainder of housing  20  will remove the insulating coating only in the reduced inner diameter portion  24  of housing  20 , and may include a portion forward of the reamer or boring tool portion for substantially contemporaneously cutting opening  28  in the forward end of housing  20 . A housing  20  so formed by gun boring may have a cylindrical outer shape or other outer shape, as is desired. 
     Flashlight  10  as described provides the advantages of a very small diameter housing  20  and a relatively high intensity light source  110  that has very long useful life, e.g., in excess of 100,000 hours, and operates for a long time, e.g., over 10 hours, on a set of batteries. An additional advantage obtains due to the water resistance provided by O-rings  116 ,  38  and  214  providing seals between the light source  110  and housing  20 , tail cap  40  and housing  20 , and pushbutton  210  and tail cap  40 , respectively. 
     While the present invention has been described in terms of the foregoing exemplary embodiments, variations within the scope and spirit of the present invention as defined by the claims following will be apparent to those skilled in the art. For example, a clip may be installed onto housing  20  to provide a simple means for securing flashlight  10  in the pocket of a user&#39;s garment or apron or the like. In addition, either or both of housing  20  and tail cap  40  may be knurled to provide a better gripping surface for facilitating the relative rotational movement of housing  20  and tail cap  40  for the turning on and off of flashlight  10 . 
     In addition, protective electrical resistor  130  of light source assembly could be eliminated or could be replaced by another electrical device, e.g., a field-effect transistor current limiter, that would limit the current that could flow through LED light source  110  to a safe level.