Patent Abstract:
A low profile lighting apparatus is characterized by a battery housing, a rail-engaging plate connected to the housing by a pair of arms, and a recessed activating push-button located between the arms and adjacent the rail-engaging plate. A flexible resilient tab, also recessed between the arms, secures the apparatus to a rail. A lock-out switch is built into a plug for closing an end of the housing. The plug has three discrete rotational positions, one for attachment, a second for activation of an illumination source, and a third for preventing accidental activation of the illumination source by requiring simultaneous axial pressure and rotation. Instead of the plug, a hinged door having a sliding latch part can be utilized. The sliding latch part includes a pair of resilient legs that cooperate with surfaces inside the door to urge the latch part toward a latching condition.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority on the basis of provisional application 61/433,304, filed Jan. 17, 2011. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to lighting, and in particular to a personal, battery-powered, light adapted to be worn by an individual on headgear or on an article of clothing, or to be mounted removably on a surface of an article. 
     BACKGROUND OF THE INVENTION 
     There has been a need for reliable, light-weight devices to provide illumination for use by individuals in order to read or perform work at night or when situated in locations such as in tunnels, caves and the like where insufficient light is available. Such lighting devices have both civilian and military applications, and various personal lighting devices have been proposed. These include devices that can be fastened to headgear, to belts or straps, to articles of clothing, to weapons, and to surfaces of other articles. 
     In military applications, especially in combat, it can be important for an individual to avoid revealing his or her location inadvertently to an enemy combatant. Consequently, there is also a need for a lighting device that can be disabled by the user and in which accidental activation is reliably prevented. 
     In military and other applications, it is also very desirable for the personal lighting device to be readily attached to, and detached from, a helmet or other article, and to be at the same time compact and not easily dislodged or damaged by accidental contact with other objects. 
     In some applications of a personal lighting device it is also desirable to provide for a moisture-tight, but easily operated, closure on the device&#39;s battery compartment. 
     SUMMARY OF THE INVENTION 
     The lighting apparatus according to the invention is designed to provide a compact and reliable source of illumination that is particularly resistant to accidental activation but nevertheless easy to use. A preferred embodiment of the invention is a low profile lighting apparatus characterized by a battery housing, a rail-engaging plate spaced from the housing and connected to the housing by a pair of arms, and a recessed activating push-button located between the arms and adjacent the rail-engaging plate. 
     In one broad aspect, the lighting apparatus according to the invention comprises a housing containing an electrochemical source of electric current, an illumination source connected to the housing, and a control connected to the housing for switching electric current supplied by the electrochemical source within the housing to the illumination source. The apparatus also includes an arm structure comprising first and second arms fixed to the housing and extending therefrom in spaced, substantially parallel, relation to each other. A mounting element, connected to the arm structure, is provided for engaging a supporting rail. The mounting element is situated on a first side of the arm structure, at a location spaced from the housing. The control includes a switch supported by the arm structure and disposed between the arms. The switch includes a push-button recessed from a second side of the arm structure opposite from the first side. The push-button is manually accessible for operation by insertion of a finger into a space between the arms. Electrical connections are provided between the switch and the housing for delivery of electric current from the electrochemical source, through the switch, to the illumination source. 
     In a preferred embodiment, the arm structure, the mounting element, and the switch together define a water-tight, sealed, compartment for containing at least parts of the electrical connections. Optionally, the mounting element can be in the form of a plate attached to the arm structure to form a closure for the compartment. 
     The housing is preferably substantially in the shape of an elongated circular cylinder, with the illumination source connected to the housing at one end of the cylinder. The electrochemical source is an electrochemical cell located within the housing, and the control preferably includes a second switch located at an opposite end of the cylinder. The second switch can have a first position in which delivery of electric current to the illumination source is permitted and a second position in which delivery of electric current to the illumination source is disabled. Where the housing is substantially in the shape of an elongated circular cylinder and the illumination source is connected to the housing at one end of the cylinder, the cylinder can have a removable plug at its end opposite from the end to which the illumination source is connected. The electrochemical source can be an electrochemical cell located within the housing, and a spring, mounted on the plug, can be in contact with the electrochemical cell. In this embodiment, the second switch can be constituted by a first contact fixed to the plug and connected to the spring, and a second contact fixed to the cylinder. The plug can be rotatable and can include a radial pin cooperating with a circumferential slot in the cylinder, the slot having an opening for allowing axial passage of the pin for removal and attachment of the plug when the plug is rotated to a first rotational position, a first detent for engaging the pin and thereby holding the plug against rotation when the plug is rotated to a second rotational position, and a second detent for engaging the pin and thereby holding the plug against rotation when the plug is rotated to a third rotational position. The contact fixed to the plug and the contact fixed to the cylinder can be in contact with each other when the plug is in its third rotational position, and out of contact with each other when the plug is in its second rotational position. The pin is disengageable from the detents for rotation by movement along an axis extending from one end of the cylinder to the other end of the cylinder, preferably against an axial force exerted by said spring. The illumination source can comprise plural light-emitting diodes. 
     A flexible locking tab is preferably disposed between the arms for engaging a locking notch on a supporting rail to prevent movement of the lighting apparatus along the rail. 
     Cross-sections of the mounting element transverse to a first direction preferably have an external dovetail-shaped cross-section capable of sliding engagement with an undercut dovetail-shaped slot in a rail. 
     According to another broad aspect of the invention an opening is provided in the housing for insertion and removal of the electrochemical source. A door, hinged to the housing, is provided for closing the opening. A latch for maintaining the door in a closed condition comprises a slot formed on a part of the housing, and a movable latch part mounted for sliding movement in the door and having a protrusion extending in a first direction relative to said door and receivable in the slot. 
     The movable latch part, which can be formed as a unitary molded part, comprises a pair of resilient legs extending along a second direction opposite to said first direction, in opposed, spaced relation to each other. The movable latch part has a pair of oppositely facing surfaces, composed of surface on each leg. These surfaces can face away from each other. A guide formed in the door constrains the movable latch part for linear movement relative to the door along the aforementioned first and second directions. The guide includes a pair of spaced, surfaces respectively engaged with the oppositely facing surfaces of the movable latch part. The surfaces of the guide exert forces on the legs causing the legs to be bent resiliently. At least the surfaces of one of the two pairs of surfaces are disposed in oblique relation to the first and second directions such that the forces exerted on the legs of the latch part by the surfaces of the guide produce a resultant force that urges the movable latch part in the first direction such that its protrusion is maintained in the slot. A manually operable slide, extending through the door, is engageable with the movable latch part, allowing the movable latch part to be urged in the second direction against the resultant force, for releasing the protrusion from the slot. 
     A sealing ring is provided to establish a fluid-tight seal between the door and the housing for sealing the compartment containing the electrochemical source. The sealing ring fits an interface between the door and the housing at the location of the opening of the housing when the door is in its closed condition. The sealing ring can be disposed in an annular groove formed in a circumferential surface of the door, and is movable with the door. 
     Among the advantages of the various aspects of the lighting device is the fact that its operating push button is recessed and therefore resistant to accidental activation. The lighting device has another significant advantage when the battery compartment plug is used as a “lock-out” switch for intentional disablement of the illumination source by rotation of the plug to a lock-out position. The recessed locking tab also provides for secure and reliable attachment to a mounting rail while making the device readily removable when the user intends to remove it. Other advantages of various aspects of the invention include structural simplicity, water-resistance, small size, ease of use, and resistance to accidental detachment from a mounting device. The embodiment having the hinged door exhibits other advantages, including superior sealing of the battery compartment, and simplicity and reliability of the door latch mechanism. 
     Further objects and advantages of the invention will be apparent from the following description when read in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of an embodiment of a lighting apparatus according to the invention; 
         FIG. 2  is an oblique perspective view showing a side thereof on which a manually operable push-button is provided; 
         FIG. 3  is another oblique perspective view showing a side thereof on which a rail-engaging member is provided; and 
         FIGS. 4 and 5  are cross-sectional views, taken respectively on a longitudinal plane and a transverse plane, of another embodiment of a lighting apparatus according to the invention, illustrating details of a hinged battery compartment door having a moisture-tight seal and a slide-operated latch mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 2 and 3 , the principal components of the lighting apparatus are its housing  10 , its illumination source  12 , a flexible “gooseneck” sheath  14  extending from one end of the housing to the illumination source, and a mounting element  16  by which the housing can be attached to a supporting rail (not shown). 
     The housing  10  can be composed of any of various materials, but is preferably molded from a suitable resin such as ABS or polyamide. As shown in  FIG. 1 , the housing is preferably in the form of an elongated, substantially circular, cylindrical body  18  having a hollow interior for containing an electrochemical current source such as a conventional 1.5 volt “AA” cell  20 . The housing has an opening  22  at one end for receiving the AA cell  20 , and a fitting  24  at its opposite end for attachment of the gooseneck sheath  14 . 
     The illumination source can include one or more light-emitting diodes (LEDs). In the embodiment shown, the illumination source  12  includes three such LEDs  26 ,  28  and  30 , secured in a support  32 . The LEDs and the support are enclosed within a head composed of a rear shell  34 , a front shell  36 , a gasket  38  and a transparent lens  40 . The rear shell  34  includes a fitting  42 , which is connected to the end of gooseneck  14  remote from housing  12 . 
     The LEDs can be in any of various combinations. For example, one LED can emit white light, and the other two LEDs can emit light is different colors. Selection of the LEDs and control of their illumination intensity is preferably carried out by means of electronic circuitry on a printed circuit board  44 , which responds to a sequence of depressions of a momentary switch  46  built on to the circuit board. A first depression of the switch, for example, can activate a red LED at a low level of illumination, subsequent, appropriately timed, depressions can produce various other illumination modes. After a suitable interval following a last depression of the switch, another depression of the switch can cause the illumination source to be switched off. A typical circuit for producing different illumination modes in response to depressions of a single set of contacts is described in U.S. Pat. No. 6,952,084, granted Oct. 4, 2005, the disclosure of which is incorporated by reference. 
     The housing  10  is provided with an arm structure comprising first and second arms  48  and  50 , fixed to the cylindrical body  18  of the housing and extending downward therefrom in spaced, substantially parallel, relation to each other. Upper and lower connecting elements  52  and  54 , which extend from one arm to the other, along with the arms define a rectangular opening  56 , through which a flexible push button  58  is exposed, as shown in  FIG. 2 . It is through manual depression of push button  58  that a user can activate the contacts of circuit board switch  46 , which is situated directly behind the flexible push button. As shown in  FIG. 2 , the push-button is in a recessed position between arms  48  and  50 , and therefore resistant to accidental activation. 
     The flexible push button  58  cooperates with the arms  48  and  50 , and with the connecting elements  52  and  54 , to seal the opening  56  ( FIG. 1 ). As shown in  FIG. 1 , a structure composed of arms  48  and  50  and connecting elements  52  and  54  forms a part of an circuit board compartment that is closed off by a closing member  60 . A thin gasket  62 , associated with the push-button  58 , is situated between the closing member  60  and the structure composed of arms  48  and  50  and connecting elements  52  and  54  to provide a water-tight seal. 
     The closing member  60  includes mounting element  16 , which is in the form of a plate the cross-sections of which, in planes transverse to the direction of elongation of the cylindrical housing body  18 , have an external dovetail-shape whereby the plate is capable of sliding engagement with an undercut dovetail-shaped slot in a supporting rail (not shown). A spring-loaded ball  63  is incorporated into the plate to exert pressure on a wall of the rail in order to maintain the oblique edges of the plate in tight engagement with the undercut parts of the rail. Although the dove-tail shape is preferred for the mounting element, other shapes that match other supporting rail configurations can be adopted. 
     As shown in  FIGS. 2 and 3 , a resilient, flexible tab  64  depends from the cylindrical housing body. This tab is cooperable with locking slots (not shown) provided at intervals along a mounting rail, for securing the lighting apparatus against longitudinal movement along the rail. Tab  62  is recessed between arms  48  and  50  so that it is resistant to accidental operation, but readily accessible by the user for manual disengagement of the lighting apparatus from the mounting rail. 
     An upwardly extending part  66 , generally in the shape of a question mark is provided at the forward end of the closing member  60 . The curved portion of part  66  fits a correspondingly shaped slot  68  in the side of the cylindrical housing body  18  adjacent the forward end to close off a space through which electrical connections can be made between the circuit board, the illumination source, and the electrochemical source. 
     The opening  22  of the cylindrical housing body can be closed by a plug  70 , to which is fixed a transverse pin  72  both ends of which protrude from the plug. The plug is provided with a sealing ring  76  which forms a water-tight seal with the interior wall of housing body  18 . Also affixed to the plug is a metal coil spring  78 , which presses against the negative terminal  80  of cell  20 . The coil spring is fixed to the plug in such a way that it rotates with the plug. An end  82  of the spring serves as a switch contact, which can engage a part  84  of a metal contact element  86  affixed to the inner wall of the housing body. 
     The plug has three distinct rotational positions determined by cooperation of the protruding ends of pin  72  with a pair of circumferential slots  88  and  90  formed on opposite sides of the housing body adjacent the opening  22 . In a fully counterclockwise rotational position the protruding ends of pin  72  are in register with longitudinal slots (not shown) extending from the opening  22  along the inner wall of the housing body. When the pins are in register with these longitudinal slots, the plug can be pushed manually into the slot, compressing spring  78 , until the pin is in register with circumferential slots  88  and  90 . With the pin in register with the circumferential slots, the plug can be rotated fully clockwise until the protruding parts of the pin reach the ends of the circumferential slots. When manual pressure on the plug is released, the spring pushes the plug slightly outward causing the pins to enter notches at the ends of the slots, one such notch being notch  92  seen in  FIG. 3 . Slot  88  has a similar notch. When the plug is in its fully clockwise position, the end  82  of the spring makes electrical contact with part  84  of element  86 , enabling the lighting apparatus by making a connection to the negative terminal of cell  20 . 
     The plug also has an intermediate rotational position, in which the protruding ends of pin  70  can be pressed by the spring  78  into notches  94  and  96  in circumferential slots  88  and  90 , respectively, and thereby held against rotation unless a positive axial force and a rotational force are simultaneously exerted on the plug. While the plug is in its intermediate rotational position, the end  82  of the spring is out of contact with part  84  of element  86 , thereby disabling the lighting apparatus altogether by depriving the circuit and the illumination source of electric current. Since the manipulation required to engage spring end  82  with part  84  is readily performed, but not easy to perform unintentionally, the intermediate position of the plug can be used as a “safety” or “lock-out” position, providing reliable assurance against accidental activation of the illumination source. 
     The positions of the protruding ends of ends of the pin may not be readily determinable. Accordingly, a pointer  98  formed on the plug can be used to indicate the pin positions visually or by feel. 
     The embodiment depicted in  FIGS. 4 and 5 , can be similar to the embodiment of  FIGS. 1-3  in all respects, except that, instead of having a battery compartment plug that also serves as a lock-out switch, the housing is provided with a hinged battery compartment door having a unique latch mechanism. 
     As shown in  FIG. 5 , an electrochemical current source  100  is disposed in a compartment  102  in a housing  104 , which is generally similar to housing  10  in  FIGS. 1 and 3 , except that it lacks the plug-receiving features such as the notched slots  88  and  90 . An opening  106  is provided at an end of the housing for insertion and removal of the electrochemical source  100 . A door  108  is connected to the housing by a hinge ( FIG. 5 ) comprising a pin  110 , extending across the gap between a pair of ears  112  on the housing and through a knuckle  114  on the door. The door is shown in a closed condition, in which an annular part  116  of the door fits into opening  106 . A resilient sealing ring  118 , which sits in an annular groove  120  on the outer peripheral surface of part  116 , and which moves with the door, fits into an annular mating groove  122  in the opening  106  when the door is in its closed condition to establish a fluid-tight seal to prevent moisture from entering compartment  102 . 
     The door carries a coil spring  124  for engaging the negative terminal of the electrochemical current source. This spring also makes an electrical connection to a contact  126 , which is connected to a current-carrying strip  128 . A stop  130  limits movement of the door in the closing direction. The door  108  can be swung to a fully open position for removal of the electrochemical current source  100 . 
     The door is maintained in a closed condition by a latch that comprises a slot  132  formed on a part of the housing that extends beyond the opening  106 , and a movable latch part  134 , mounted for sliding movement in the door and having a protrusion  136  that is received in the slot  132 . 
     The movable latch part  134  comprises a cross member  138  from which the protrusion  136  extends in a first direction, and a pair of resilient legs  140  and  142  that extend from the cross member in a second direction opposite to the first direction. The legs are disposed in opposed, spaced relation to each other. The movable latch part has a pair of outwardly facing surfaces composed of an outer surface  144  on leg  140  and an outer surface  146  on leg  142 . Surface  144  faces away from leg  142  and surface  146  faces away from leg  140 . The movable latch part can be a unitary molded part. That is, the cross-member  138 , the legs  140  and  142 , and the latching protrusion  132  can be molded as a unit from any suitable resilient plastic resin. 
     A guide formed in the door constrains the movable latch part for linear movement relative to the door along the aforementioned first and second directions. The guide includes a pair of spaced, opposed, inwardly facing surfaces  148  and  150 , respectively engaged with the outwardly facing surfaces  144  and  146  of the movable latch part. The inwardly facing surfaces of the guide exert inward forces on the legs causing the legs to be bent resiliently toward each other. In the embodiment shown in  FIG. 5 , outer surfaces  144  and  146  on the legs of the movable latch part are disposed in oblique relation to the direction of movement of the movable latch part such that the forces exerted on the legs of the latch part by the inwardly facing surfaces of the guide exert a camming action, producing a resultant force that urges the movable latch part in the first direction such that its protrusion is maintained in the slot. The inwardly facing surfaces  148  and  150  of the guide are also disposed in oblique relation to the direction of movement of the guide such that the resultant force urges the movable latch part in the first direction. Although surfaces  144 ,  146 ,  148  and  150  are all oblique in the embodiment illustrated in  FIGS. 4 and 5 , a similar result can be achieved if only surfaces  144  and  146  are oblique, or if only surfaces  148  and  150  are oblique. 
     A slide  152 , extending through the door and having a manually engageable surface  154 , has an upstanding part  156  that engages both legs of the movable latch part. As shown in  FIG. 4 , upstanding part  156  and the legs of the movable latch part are disposed between internal walls  158  and  160  formed in the door. The slide also has a downwardly protruding part  162  engaged with the cross-member  138  of the movable latch part. The downwardly protruding part and cross-member  138  are similarly disposed between internal walls  158  and  160 . Because the spacing of walls  158  and  160  is only slightly greater than the sum of the thickness of the movable latch part and the maximum thickness of either of parts  156  and  162 , the movable latch part  134  and the slide  152  are constrained so that they move only along the first and second directions. 
     An upwardly facing surface  166  of the slide engages the bottom of a projection  168  of the movable latch part so that, when the slide is pushed upward manually, the movable latch part moves in its second direction, against the resultant force exerted on the latch part as a result of the resiliency of its legs, so that protrusion  136  is released from slot  132 , allowing the door  108  to be opened. 
     Many modifications can be made to the lighting apparatus described. For example, in the first embodiment, although two circumferential slots are used to receive opposite ends of the pin, a similar function can be achieved using a pin having a single protruding end and a single circumferential slot. The order of the three rotational positions of the plug can be modified. For example, the lock-out position in which the illumination source is disabled can be one of the end positions rather than the intermediate position. As mentioned previously, the number and kind of LEDs can be varied, as can the configuration of the mounting element. Although a single cell is preferable, plural electrochemical cells can be used to supply electric current, and the plural cells, if used, can be arranged in any of various ways. 
     In the embodiment shown in  FIGS. 4 and 5 , whereas the legs of the movable latch part are urged inward by inwardly facing surfaces of the guide, it is possible to achieve a similar result in a modification in which the legs of the movable latch part are urged outward by a guide element located between the legs. 
     Still other modifications can be made without departing from the scope of the invention as defined in the following claims.

Technology Classification (CPC): 5