Patent Publication Number: US-8974075-B2

Title: Focusable flashlight

Description:
FIELD OF THE INVENTION 
     The present invention relates to a flashlight. More particularly this invention concerns a flashlight whose light beam can be focused. 
     BACKGROUND OF THE INVENTION 
     A typical flashlight has a casing, a light source and a power source in the casing, and a lens assembly mounted at a head end of the casing. The head-end lens assembly can be shifted longitudinally or axially of the casing relative to the light source to focus light emitted by the source into a controllable beam. 
     Such a flashlight as disclosed in U.S. Pat. No. 7,040,775 has a casing adapted to hold a battery, a battery-powered LED light source mounted on the casing and directed forward along an axis, and a holder sleeve axially displaceable on the casing forward of and relative to the LED light source. An image carrier, e.g. a slide or a mask, is fixed in the holder sleeve and axially aligned with the light source. An end piece on the casing forward of the LED light source and of the image carrier holds a lens. Thus axial displacement of the holder sleeve moves the image carrier relative to the light source and to the lens. For the displaceable support of the image carrier, in addition to the lamp head and the casing, at least three further connecting sleeves are provided, namely an adapter, a guide sleeve and a sliding sleeve, so that assembly of the flashlight is relatively complex. 
     Furthermore, flashlights are known in which the lamp head focuses the emitted light with a reflector it carries and the casing with the light source are connected to one another via a threaded connection such that the reflector and the light source can be displaced relative to one another by a rotary motion. However, this embodiment has the disadvantage that two hands are always required for focusing, the casing being held with one hand and the lamp head being rotated with the other hand. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved focusable flashlight. 
     Another object is the provision of such an improved focusable flashlight that overcomes the above-given disadvantages, in particular that can be focused with one hand and for whose assembly only a small number of connecting sleeves is required. 
     SUMMARY OF THE INVENTION 
     A flashlight has according to the invention a casing extending along an axis and having a front end, a light source axially secured in the housing inward of the front end, and a two-part connecting sleeve forward of the light source and having a rear part secured in the housing and a front part. Interengaging formations couple the parts together for only limited axial movement relative to each other, but lock them rotationally and prevent axial separation beyond a predetermined limit. A lens is mounted in the front part. A head sleeve secured to the front part extends axially rearward over the front end of the casing so that relative axial movement of the front and rear parts axially shifts the lens relative to the source. The result is a particularly compact focusable flashlight that is is easy to manufacture and easy to operate. Due to the low number of components used, assembly costs are also reduced. 
     Further preferred embodiments of the present invention are described below as well as in the subordinate claims. According to a first embodiment, the parts are cylindrically tubular and each have respective screwthreads that join them to complementary screwthreads on the lamp head and casing. Alternatively, the parts can also be connected via a bayonet or another detachable connection, such as, for example, a locking connection, to the casing or to the lamp head. However, a threaded connection is preferred due to the ease of production and assembly. 
     So that the lamp head can be displaced with respect to the casing, one part has at least one slide arm or guide that extends longitudinally axially and engages a slide surface or arm embodied on the other part. Preferably, the slide arm is of in a cylindrical or partly cylindrical shape. In an embodiment with a cylindrical slide arm, the other part is preferably annular and, guides are provided between the annular part and the guide, so that rotary movement of the annular part is prevented. In an embodiment with a plurality of partially cylindrical slide arms, they are preferably spaced equiangularly. The number of slide arms can vary depending on the size of the flashlight, at least three slide arms and three guides are preferred. 
     So that the lamp head is not accidentally detached from the casing during focusing, a captive connection of the parts is provided in an advantageous manner, that is the two parts can move relative to each other, but full separation is impossible. To this end, the guide preferably has a stop and the slide arm has an enlarged head part. The relative movement of the parts with respect to one another is limited on the one hand by the confronting and axially engageable end faces of the parts themselves and on the other hand by the stop and the enlarged head part. In an embodiment with several slide arms, the expansions can be tangential, and in an embodiment with one annular slide arm, the enlarged head part can be an annular stop that forms a stop with the front side of the annular part. It is preferably provided that the guides are on the outside or the inside of the part. In particular with a single annular slide arm, the guide is arranged on the inside for reasons of construction. Otherwise, the thread is interrupted by the guides at least in some regions. 
     In order to prevent the lamp head from being accidentally displaced with respect to the casing and thus to the light source, one guide element is preferably arranged so that relative movement of the parts can be performed only against a force. In the simplest case the guide element is an O-ring of rubber or another elastic material, which on the one hand surrounds the casing and on the other hand is sized such that so great a friction is produced between the lamp head and the O-ring that the lamp head can be displaced only deliberately. A guide element of this type can be produced economically and is easily replaced in the case of wear. In addition, the guide element serves as a seal so that no dirt in the form of dust can into the lamp head. 
     The connecting sleeve is preferably make by injection molding of plastic or is produced from metal, in particular aluminum. 
     According to a further embodiment of the present is invention the light source is an LED carried on a holder plate. This holder preferably has electric contacts concentrically in a circular or annular layout on its rear face. These contacts are connected to corresponding electrical contacts of the batteries. Furthermore, the holder has on the rear side an annular mating surface formed of a heat-conducting material and is in abutment with the casing. The heat produced in the light source is hereby dissipated to the casing, which in particular increases the service life of the light source. Aluminum, brass or copper are in particular suitable as materials. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which: 
         FIG. 1  is an axial section through a flashlight according to the invention with no batteries installed and in partially disassembled condition; 
         FIG. 2  is a view of a flashlight with no batteries or end cap in assembled condition; 
         FIG. 3  shows the casing, light source, and connecting sleeve according to the invention; and 
         FIG. 4  is a lare-scale persopective view of the connecting sleeve. 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIGS. 1-3  a flashlight  1  according to the invention has a tubularly cylindrical casing  2  centered on an axis A, a light source  3 , a lens  4  and a tubular head sleeve  5 . A connecting sleeve  6  connected on the one hand to the casing  2  and on the other hand to the lamp head  5 . To this end the sleeve  6  has an external screwthread  7   a  complementary to an internal screwthread  7   b  of the head  5  and an external screwthread  7   c  complementary to an internal screwthread  7   d  of the casing  2 . 
     The light source  3  is carried on a holder disk  8  that is seated on a forwardly directed shoulder  10  of the casing  2 . When assembled, the holder disk  8  is pressed by the connecting sleeve  6  onto the shoulder  10  and thus positively fixed in the casing  2 , which forms a battery compartment rearward of this disk  8 . Electrical contacts  11  as well as a heat-conducting surface  12  are provided on the back face of the holder  8 . 
     The front end of the head  5  carries the lens  4  so that it can be longitudinally or axially steplessly displaced on the housing between the positions shown in  FIGS. 1 and 2 . In  FIG. 1  the attachment lens system  4  bears against the holder plate or disk  8 , whereas in  FIG. 2  the disk  8  and the attachment lens system  4  are at a spacing S from each other. In order to prevent accidental shifting of the lamp head  5  and thus of the attachment lens system  4 , an O-ring  9  is provided that is set in an outwardly pen groove on the casing  2  and bears elastically outward on an inner surface of the lamp head  5 . 
     In  FIG. 4  the connecting sleeve  6  is shown to have two separate parts  41  and  42  that can move limitedly along the axis A relative to each other. To this end, the part  41  has three axially extending, angularly equispaced, and radially outwardly open guide grooves  43 ,  43 ′,  43 ″ each with a wide head region delimited by outwardly directed shoulders  46 . The other part  42  has axially extending guide arms  45 ,  45 ′,  45 ″ axially slidable in the guide grooves  43 ,  43 ′, and  43 ″ and each having a widened head  44 . The arms  45 ,  45 ′, and  45 ″ are sufficiently long that their heads  44  can shift axially in the respective grooves  43 ,  43 ′,  43 ″ outward of the shoulders  46 . The heads  44  and the stops  46  abut each other when the parts  41  and  42  are displaced axially from one another to the maximum spacing S. At the same time, the interfit of the arms  45 ,  45 ′, and  45 ″ in the grooves  43 ,  43 ′, and  43 ″ rotationally couples the two parts  41  and  42  together to that they can be screwed into the casing  2  and into the head sleeve  5 .