Patent Publication Number: US-6220720-B1

Title: Flashlight

Description:
SUMMARY OF THE INVENTION 
     This invention relates to flashlights, and particularly to improvements in water-resistant flashlights. 
     Conventional flashlights typically incorporate sliding switches in the sidewalls of their battery compartments. Such switches are subject to corrosion and wear, and have been notoriously unreliable. Moreover, because they are subject to leakage, they have been generally unsuitable for use in flashlights intended for underwater use. 
     These drawbacks of conventional flashlight switches have led to the use of rotatable head flashlights in which the battery compartment has no switch and is entirely water-tight, and in which a head, containing an assembly comprising a bulb, a parabolic reflector and a lens, is threaded onto the battery compartment. In rotatable head flashlights, switching is accomplished by rotation of the head relative to the battery compartment. Rotation of the head on the threads of the battery compartment causes the head to move axially, bringing contacts together, or separating them, depending on the direction of movement of the head. A water-tight seal is maintained between the head and the battery compartment, usually by an O-ring or other suitable sealing device. In some cases one of the contacts is a metal portion of the bulb itself. In others a battery terminal or a part of the battery case is used as one of the contacts. The use of portions of the bulb or portions of a battery or battery case as contacts has the advantage of reducing cost, but sometimes produces unreliable operation. Various other switching devices designed for cost reduction also give rise to a risk of unreliable operation. Still others utilize more complex head assemblies in the interest of reliability. 
     Reliability is, of course, an especially important consideration in underwater flashlight design, and an important object of this invention is to provide an inexpensive, water-resistant flashlight having a highly reliable switch. 
     The flashlight in accordance with the invention comprises a battery compartment having first and second opposite ends, and an internal space for containing an electrical energy source having a pair of terminals. The compartment is entirely closed except for a opening at one of the opposite ends, and has threads adjacent the opening. A head assembly, including a lens, has threads engaged with the threads of the battery compartment and provides a fluid-tight closure for the opening of the battery compartment. The operation of the threads moves the head assembly axially relative to the battery compartment as it is rotated. A bulb carrier assembly, supporting miniature incandescent bulb, is receivable through the opening of the battery compartment. The bulb carrier includes a reflector arranged to direct light generated by the light bulb through the lens. The bulb carrier is engageable by the head assembly and movable axially by the head assembly. 
     The bulb carrier has a pair of electrical terminals engageable with the terminals of the electrical energy source. The bulb carrier also has a normally open switch comprising at least two contacts one of which is movable relative to the bulb carrier. The contacts of the switch are carried by the bulb carrier, and conductors provide a series circuit through the bulb, the switch and the pair of electrical terminals. The battery compartment includes a surface engageable with the movable contact of the normally open switch, and positioned to urge the movable contact in a direction to close the series circuit when the head assembly moves the bulb carrier axially in a first direction relative to the battery compartment. 
     In a preferred embodiment of the invention, the carrier includes a printed circuit board on which the conductors are printed, and on which both electrical terminals, and the contacts of the switch, are mounted. 
     The board optionally has a socket mounted on it, removably receiving, and providing electrical connections to, the bulb. In the preferred embodiment, the switch includes three contacts, the movable contact being a resilient, bridge-like element overlying both of the other contacts. The surface engageable with the resilient element is preferably a molded shelf formed on the interior wall of the battery compartment. 
     Preferably, a spring in the battery compartment urges an electrical energy source in the battery compartment in a direction such that the terminals of the electrical energy source are continuously held in contact with the pair of electrical terminals of the bulb carrier. The electrical energy source preferably comprises a pair of cells disposed in side-by-side relationship and connected electrically in series. 
     Interengaging elements on the battery compartment and the bulb carrier may be provided to prevent rotation of the bulb carrier with the head assembly while permitting axial movement of the bulb carrier relative to the battery compartment. 
     Other objects, details and advantages of the invention will be apparent from the following detailed description when read in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the exterior of a flashlight in accordance with the invention; 
     FIG. 2 is an exploded view of the flashlight; 
     FIG. 3 is a partially broken away view of the battery case portion of the flashlight; 
     FIG. 4 is an plan view showing details of the circuit board on the bulb carrier assembly, including the battery-contacting terminals and the switch; 
     FIG. 5 is an elevational view of the bulb carrier assembly; 
     FIG. 6 is a broken-away perspective view showing the bulb carrier assembly in the battery case, and illustrating the operation of the switch; and 
     FIG. 7 is a sectional view of the bulb carrier taken on plane  7 — 7  in FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, the flashlight in accordance with the invention comprises a battery compartment  10  and a head assembly  12 . The head assembly comprises a lens  14  mounted in a hollow barrel  16 , which preferably has ribs  18  to facilitate manual gripping and rotation of the head assembly relative to the battery compartment. The battery compartment  10  is preferably an injection-molded, unitary element having a blind interior terminating in a closed end  20  having an external tab  22  with a hole  24 , for connection to a lanyard or the like. The battery compartment is preferably designed to hold two cylindrical 1.5 volt “AAA” cells mechanically in parallel relationship to each other, but electrically in series. Oval-shaped indentations are provided on both sides of the battery compartment to facilitate gripping, one such indentation being shown at  26 . The end of the battery compartment adjacent the head assembly is flared at  28 . 
     The exploded view of FIG. 2 shows that the battery compartment has an externally threaded extension  30  on the flared part  28 , and that the barrel  16  has internal threads  32 , which are engageable with the threads on extension  30 . The threaded extension  30  is provided with an O-ring  34 , which fits a cylindrical inner wall  36  of barrel  16 . 
     Because of the cooperation of the threads, rotation of the head assembly relative to the battery compartment causes the head assembly to move axially relative to the battery compartment through a short distance. The cylindrical inner wall  36  of the barrel  16  slides on O-ring  34 , while compressing the O-ring to maintain a water-tight seal. 
     The flashlight also includes a bulb carrier assembly  38 , which preferably comprises a molded body  40  with a flared end  42  which is engageable with an annular surface  44  inside the head assembly. A printed circuit board  46  is mounted at the opposite end of bulb carrier assembly, 38 . The circuit board carries, on the side visible in FIG. 2, a pair of contacts  48  and  50 , and a switch  52 . A bulb-receiving socket (not shown in FIG. 2) is mounted on the opposite side of the circuit board. The bulb carrier assembly includes a parabolic reflector (not shown in FIG.  2 ), which can be a metallized inside surface of molded body  40 . A slot  54 , extending in the longitudinal direction of the flashlight, is formed on the outer surface of the bulb carrier assembly. 
     FIG. 3 shows the battery compartment  10  with an electrical energy source consisting of two type “AAA” cells  56  and  58 , arranged mechanically in parallel relationship to each other, and connected electrically in series through a spring  60  inside the battery compartment. The spring consists of a single wire wound into two coils  62  and  64 , connected to each other by an interconnection  66 . The positive terminal  68  of cell  58  and the negative terminal  70  of cell  56  are exposed through the opening  72  in externally threaded extension  30 . The springs not only make the series electrical connection between the cells, but also allow for axial movement of the cells while their series connection between terminals  48  and  50  (FIG. 2) is maintained. 
     As shown in FIG. 3, the interior of the battery compartment has formed on it a small, shelf surface  74 , which, as will be seen, is engageable by an element of switch  52 . A molded key  76  extends axially from the location of the shelf surface  74  along the inner wall of extension  30 . This molded key  76  slides in slot  54  and the cooperation of key  76  and slot  54  prevents rotation of the bulb carrier  38  while allowing the bulb carrier to move axially. In a practical flashlight in accordance with the invention, the interior of the battery compartment will have two shelf surfaces directly opposite each other and two molded keys also directly opposite each other. With this construction, the bulb carrier can be inserted in either of two orientations, 180° apart. 
     FIGS. 4 and 5 illustrate details of the circuit board  46  and switch  52 . Contact  48 , which engages terminal  70  of cell  56 , is connected by conductor  78  to bulb socket terminal  80 . The other bulb socket terminal  82  is connected through conductor  84  (which is on the side of the board opposite to the side shown in FIG. 4) to a printed switch contact  86 . Contact  50  is connected to a printed switch contact  88  through conductor  90 . 
     Switch contacts  86  and  88  are normally disconnected from each other, but can be electrically connected together by a third contact in the form of a resilient spring metal bridge  92 , which is anchored to the circuit board at  94  and  96 . The bridge  92  overlies both contacts  86  and  88 , and has dimples  98  and  100 , which are positioned so that they touch contacts  86  and  88  respectively when bridge  92  is flexed by a force exerted on it by shelf surface  74  (FIG.  3 ). 
     The manner in which the surface  74  approaches the bridge of switch  52  is best shown in FIG.  6 . This figure also shows the key  76 , which extends into slot  54  to prevent the bulb assembly from rotating as the head assembly  12  is rotated. 
     FIG. 7 shows the bulb carrier  38 , with the two pins of a bulb  102  removably inserted into socket connectors  106  and  108  on the side of the circuit board opposite to the side on which contacts  48  and  50  are located. 
     In operation, the circuit to the bulb is completed by twisting the head assembly clockwise, causing the bulb carrier to be pushed axially by annular surface  44  toward the blind end  20  of the battery compartment. The springs  62  and  64  allow the energy cells  58  and  56  to move axially as the bulb carrier is pushed, and at the same time maintain contact between energy cell terminal  68  and circuit board contact  50  and between energy cell terminal  70  and circuit board contact  48 . Shelf surface  74  presses on bridge  92  of switch  52 , closing the switch. By virtue of its use of a circuit board-mounted switch, the flashlight of the invention operates with high reliability, there being no use of an element of the bulb itself as a switch contact, and no use of cooperating switch elements mounted respectively on the battery compartment and on the head assembly. The flashlight is simple to manufacture, as all of the electrical switching parts, bulb socket elements and energy cell contacts are circuit-board mounted. 
     Although the circuit board-mounted switch can consist of one fixed contact and one resilient, movable contact, preferably the switch is a three-contact switch comprising two fixed contacts on the circuit board and an overlying, bridge-like, resilient element arranged to be urged into contact with both of the fixed contacts. The bridge-like element improves the reliability of opening of the switch. 
     Various modifications can be made to the flashlight described. For example, the battery compartment can be designed to hold a single energy cell, such as a “C” or “D” type cell, in which case one of the energy cell contacts on the circuit board may be centered on the board, and a conductor may be provided in the battery compartment to extend one of the energy cell terminals to a location such that it engages another energy cell contact appropriately positioned on the circuit board. alternatively, the battery compartment can be sized to hold “AA” cells, or elongated so that it can hold more than two cells, for example four “AAA” cells connected in series in a two-by-two arrangement. 
     Although, in the embodiment described, the bulb is mounted removably in a socket on the circuit board, the pins of the bulb can be instead soldered directly to conductors on the circuit board, in which case the circuit board can be replaced along with the bulb, when the bulb filament burns out. If the circuit board is permanently attached to the reflector, the entire bulb carrier assembly can be replaced. 
     Still other modifications may be made to the apparatus and method described above without departing from the scope of the invention as defined in the following claims.