Abstract:
Disclosed is a downlight ( 100 ) comprising an annular mounting frame ( 50 ) to be mounted in the area of a ceiling mounting hole, and a light fixture ( 10 ) that is to be fastened to the mounting frame ( 50 ) and includes a luminaire head ( 30 ) thereon. The mounting frame ( 50 ) and the light fixture ( 10 ) are designed such that the light fixture ( 10 ) is fastened to the mounting frame ( 50 ) by twisting the former ( 10 ) relative to the latter ( 50 ), additional securing means being provided which prevent the light fixture ( 10 ) from being twisted in the unlocking direction in a mounted position.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is the U.S. national stage application of International Application PCT/EP2015/074315, filed Oct. 21, 2015, which international application was published on Apr. 28, 2016 as International Publication WO 2016/062744 A1. The International Application claims priority of German Patent Application 20 2014 105 017.5, filed Oct. 21, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a downlight, having an annular mounting frame to be mounted in the region of a ceiling mounting hole, and a so-called light fixture to be attached to the mounting frame, having a luminaire head located thereon. In particular, the invention relates to a downlight with which the light fixture is releasably attached to the mounting frame by twisting it in relation thereto. 
       BACKGROUND OF THE INVENTION 
       [0003]    Lamps that are provided for attachment to a ceiling of a room that is to be illuminated, which are designed to project light in a substantially downward direction are normally referred to as “downlights.” These are normally recessed lamps, which are designed such that they can be mounted in the mounting holes of a suspended ceiling element, e.g. a sheetrock ceiling. 
         [0004]    Recessed ceiling lamps of this type, in the form of downlights, are know in different configurations. A classic design comprises the lamp or the light fixture having the actual luminaire head, which then contains the light source(s), basically having a circular design. An annular, mounting frame is first attached to the ceiling, and the light fixture, having the luminaire head located thereon, is subsequently releasably attached to the mounting frame. 
         [0005]    The use of this mounting frame serves to simplify the installation of the downlight, as well as later repair and maintenance measures. Specifically, only the mounting frame is permanently attached to the ceiling structure, e.g. via a screw connection or a special clamping connection, and subsequently, optionally, at least partially plastered over. The actual lamp, on the other hand, i.e. the light fixture having the luminaire head located thereon, is designed such that it can be attached to the mounting frame in a releasable manner. The actual installation of the main components of the downlight can thus occur at a later point in time, when all of the further preparations, in particular the attachment and plastering of the mounting frame, have already been completed. Furthermore, it is not necessary to fully remove all of the components in order to exchange the luminaire head, or the light source of the downlight, rather only the light fixture is released from the mounting frame and removed therefrom. The mounting frame itself, on the other hand, can remain permanently in the ceiling. 
       SUMMARY OF THE INVENTION 
       [0006]    For the solution described above, it is necessary, as a matter of course, that the attachment of the light fixture to the mounting frame is releasable, while at the same time, the connection is designed such that the light fixture having the luminaire head located thereon can be easily, quickly and reliably attached to the mounting frame. In particular, with the rotational embodiments referred to in the present invention, attachment means in the form of a screw-like connection, and in particular a so-called bayonet joint, have been implemented. In these rotational embodiments, the light fixture is placed against the mounting frame from below and then twisted in relation thereto. The light fixture is then attached to the mounting frame by means of guide projections, which are normally disposed on the light fixture and engage in the guide tracks of the mounting frame, or slide along the surface of such guide tracks. In order to release the connection, the light fixture need only be twisted in the opposite direction in relation to the mounting frame. 
         [0007]    This type of bayonet joint, described above, has proven to be very effective for downlights in many instances, but in some cases there is the problem that the light fixture attached to the mounting frame cannot be sufficiently secured. This problem exists in particular when the luminaire head retained by the light fixture can also be adjusted, and pivoted and/or rotated in relation thereto, for example. So-called Cardan lights are frequently used, in which the luminaire head can be rotated 360° in relation to the light fixture, and can also be pivoted. The mount for the luminaire head is designed in this case such that an adjustment of the luminaire head has no effect on the attachment of the light fixture to the mounting frame, but there is nevertheless the risk that when the luminaire head is twisted in one direction, which corresponds to the release of the bayonet joint, the connection between the light fixture and the mounting frame is simultaneously released unintentionally. This means that there is a risk that, when adjusting the orientation of the luminaire head, the light fixture is also unintentionally released and the lamp falls out of the mounting frame. 
         [0008]    The present invention therefore addresses the objective of providing a novel solution in which the problems outlined above are avoided. 
         [0009]    The downlight according to the invention is designed such that the attachment of the light fixture to the mounting frame occurs by twisting the light fixture in relation to the mounting frame. This can be provided, in particular, in the framework of a bayonet joint. In accordance with the invention, additional securing means are provided, which secure the light fixture against rotation in the releasing direction when the light fixture has been installed, i.e. is in the position in which it is attached to the mounting frame. 
         [0010]    Thus, in accordance with the present invention, a downlight is proposed, having an annular mounting frame that is to be installed in the region of a ceiling mounting hole, and light fixture that is to be attached to the mounting frame, having a luminaire head located thereon, wherein the mounting frame and the light fixture are designed such that the attachment occurs by means of twisting the light fixture in relation to the mounting frame, and wherein, in accordance with the invention, additional securing means are provided, which secure the light fixture against twisting in the releasing direction when it has been installed. 
         [0011]    The securing means preferably comprise a locking element, disposed in particular on the mounting frame, which is blocked, in particular, by a delimiting element disposed on the light fixture when the light fixture has been installed. It may be provided, in particular, that the locking element and the delimiting element are designed such that when the light fixture is twisted in relation to the mounting frame in the installation direction, the locking element automatically passes over, or overcomes the delimiting element. This can be achieved, for example, in that the delimiting element is formed by a so-called approach bevel, and the locking element is supported such that it can be adjusted in terms of its height. When the light fixture is twisted in relation to the mounting frame in order to attach it thereto, the height adjustable locking element slides along the approach bevel, and is deflected thereby, until it passes over it, and then snaps back in place, into a corresponding locking position, in which the locking element is blocked against a twisting in the opposite direction by the delimiting element, or the approach bevel. The solution according to the invention can be very easily implemented in this manner, without numerous additional measures. 
         [0012]    The height adjustability of the locking element can be implemented, for example, in that the locking element is formed by a locking spring, which is disposed on the mounting frame, and has a locking projection facing the interior space intended for receiving the light fixture. The fact that this relates to a flexible element thereby also ensures that the locking spring automatically snaps into a position in which, according to the present invention, the light fixture is secured against rotation in the releasing direction after passing over the approach bevel. 
         [0013]    The various components are preferably arranged such that an unintentional releasing of the locking according to the invention is prevented. This locking can only be released through targeted measures, for which it may be proposed, for example, that an unlocking hole is formed on the mounting frame, which enables the insertion of a tool for lifting the locking spring. By way of example, this hole can be very small, such that the locking can only be released by inserting a very thin object, e.g. a paper clip or a thin screwdriver, which must be inserted in this hole in a targeted manner. This measure provides, on one hand, sufficient security, and on the other hand, the effort required for releasing the lock is not very great, if the light fixture is to be intentionally removed from the mounting frame. 
         [0014]    Another further development can comprise an additional delimiting projection, by means of which a twisting of the light fixture is limited in the locking direction. I.e., this delimiting projection represents the end position of the light fixture when it is rotated in order to install it, and is preferably disposed such that the locking projection of the locking spring specified above passes into the intermediate space between the delimiting projection and the approach bevel. By this means, a defined installation position of the light fixture in relation to the mounting frame is obtained. 
         [0015]    The light fixture itself can be made of plastic, for example. It is also possible to make it out of another material, in particular sheet metal or aluminum. 
         [0016]    As has already been stated, the solution according to the invention results in advantages when the luminaire head itself can also be adjusted, in particular such that it is disposed on the light fixture in an adjustable manner. I.e., a particularly preferred exemplary embodiment of the present invention depicts Cardan lamps. The concept according to the invention can, however, also be used with luminaire heads rigidly disposed on the light fixture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention shall be explained in greater detail below based on the attached drawings. Therein: 
           [0018]      FIG. 1  shows the components of an exemplary embodiment of a downlight according to the invention in an exploded view; 
           [0019]      FIG. 2  shows the downlight according to  FIG. 1  in the assembled state; 
           [0020]      FIG. 3  shows the design of a mounting frame for the downlight; 
           [0021]      FIG. 4  shows the locking spring used as a locking element; 
           [0022]      FIG. 5  shows the mounting frame with elements for attachment to a suspended ceiling located thereon; 
           [0023]      FIG. 6  shows an enlarged view of the locking spring attached to the mounting ring; 
           [0024]      FIG. 7  shows the view of a light fixture having components thereon for implementing the securing against rotation according to the invention; 
           [0025]      FIG. 8  shows an enlarged view of a portion of the light fixture from  FIG. 7 ; 
           [0026]      FIGS. 9 a  and 9 b    show the steps for attaching the light fixture to the mounting frame according to the present invention; and 
           [0027]      FIGS. 10 a  and 10 b    show the method for releasing the locking. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Initially,  FIGS. 1 and 2  show different views of the main components of a downlight designed according to the invention, provided as a whole with the reference symbol  100 . The downlight  100  is intended to be installed in a basically circular mounting hole, not shown here, in a suspended ceiling. Light emission occurs primarily in a downward direction, toward a region that is to be illuminated. There are many uses for downlights of this type, both for lighting workspaces as well in spaces in public buildings, e.g. museums and the like. 
         [0029]    The attachment of such downlights to a ceiling construction occurs, such that initially, a first element is preferably permanently and securely connected to the ceiling, and all of the other components can be releasably mounted on this first element. An installation frame or mounting frame  50  is the element permanently connected to the ceiling, which is adapted to the mounting hole in the ceiling in terms of its shape, thus having a circular shape in the present case. As is already known from the prior art, the mounting frame  50  has an angled configuration, having a flange  51  directed outward, which bears against the ceiling in the installed state, as well as a circumferential ridge  52  extending through the hole in the ceiling. The circumferential flange region  51 , which then forms the actual mounting hole for the other components of the downlight with its inner edge, serves to compensate for, or cover any irregularities in the ceiling mounting hole. This flange  51  is frequently partially plastered over after it has been attached to the ceiling, such that a particularly inconspicuous transition is obtained between the ceiling and the other elements of the lamp  100 . 
         [0030]    The attachment of such a mounting frame  50  to the suspended ceiling can be achieved by a number of methods, wherein screw connections are known, for example, which would also be suitable in the present case. In this case, the outward protruding region of the flange  51  normally has a hole pattern or the like, which simplifies the screwing to the sheetrock ceiling. In contrast, the attachment occurs with the depicted exemplary embodiment by means of special locking elements  55 , which are distributed about the circumference of the mounting frame  50 . These locking elements are formed, in particular, by height adjustable and outward pivotable tabs, which are first oriented vertically downward in the configuration depicted in  FIG. 1 , such that they can be easily inserted through the mounting hole when the mounting frame  50  is placed in the ceiling. The locking elements  55  are first pivoted outward and pressed down in the state in which the flange region  51  bears on the undersurface of the ceiling, such that they ultimately come to bear against the upper surface of the suspended ceiling. The ceiling is then therefore clamped between the locking elements  55  on one side, and the outward protruding flange region  51  of the mounting frame  50  on the other side, such that it is securely joined to the ceiling. Locking measures of this type are already known from downlights according to the prior art, for which reason there shall be no further description thereof. 
         [0031]    The installation of the components responsible for light emission from the downlight  100  occurs in a second step. These are located in a luminaire head, which is provided with the reference symbol  30  in the present case. The luminaire head  30  contains, firstly, the light sources, e.g. in the form of one or more LEDs, the light of which is projected downward using a reflector, not shown in detail. The heat resulting during operation of the light sources is discharged into the ambient air through a cooling element  31 , which extends upward—as shown in the illustration—and is disposed inside the intermediate region between the suspended ceiling and the structural ceiling above when in the installed state. The power supply for the various components of the luminaire head  30  can be provided by a separate control and power supply unit or an appropriate integrated unit. 
         [0032]    The luminaire head  30  can thus have different designs, and for a releasable attachment to the mounting frame  50  it is retained by a light fixture  10 , designed according to the invention in the manner described in greater detail below. In the present case, it is provided that the luminaire head  30  is disposed on the light fixture  10  such that it can be adjusted. In particular, a so-called Cardan light is to be created thereby, which enables a pivoting of the luminaire head  30  in different directions, and also enables a rotating thereof, in particular. Appropriate attachment means, which provide these types of adjustment possibilities, are already known from the prior art. Alternatively, it would also be entirely conceivable that the luminaire head  30  be retained on the light fixture  10  such that it can only be rotated, or it is even rigidly disposed thereon. Furthermore, an annular aperture  35  is also provided in the depicted exemplary embodiment, which is attached to the undersurface of the light fixture  10  for optical reasons. This is not absolutely necessary, however, for implementing the concept according to the invention. 
         [0033]    The releasable attachment of the light fixture  10  to the mounting frame  50  occurs in the present case by means of a bayonet joint. This represents the typical approach for releasably attaching light fixtures for downlights to the annular mounting frames. Appropriate guide tracks  53  are provided on the inner surface of the upward directed ridge  52  of the mounting frame  50 , which can be accessed via insertion holes  54 , which extend toward the undersurface of the mounting frame  50 . In the present case, three guide tracks  53  are distributed over the circumference of the mounting frame  50 , having appropriate insertion holes  54  (see  FIG. 3 ), wherein three projections corresponding thereto are distributed over the outer circumference of the light fixture  10 . The light fixture, preferably made of plastic, has basically a pot-like design, having a circular base surface, to which the luminaire head  10  is attached, as well as a circumferential, slightly slanted, circumferential surface, on which the bayonet projections are formed. 
         [0034]    In order to attach the light fixture  10  to the mounting frame  50 , it is thus placed against the mounting frame  50  from below, such that the projections facing outward engage in the insertion holes  54 . Subsequently, the light fixture  10  is twisted in the direction of the arrow (see  FIG. 1 ), such that the projections slide along the upper surfaces of the guide tracks  53 , until the end position, or installation position, has been reached. In this case, the guide tracks  53  then ensure that the light fixture  10  can no longer fall downward, out of the hole of the mounting frame  50 . 
         [0035]    If the arrangement of the luminaire head  30  on the light fixture  10  is then such that an adjustment of the light emission can be carried out through rotating, there is then the risk that when the luminaire head  30  is rotated against the direction of the arrow in  FIG. 1 , the light fixture  10  will also be rotated in this direction, and as a result, the bayonet lock will be unintentionally released. This would mean that there is the risk that when the light emission is adjusted, the connection between the mounting frame  50  and the light fixture  10  could be loosened unintentionally, or even fully released, such that it can fall out. 
         [0036]    In order to prevent this, a special securing mechanism is provided according to the present invention, which shall be described in greater detail based on the following figures. 
         [0037]    A first substantial element of the solution according to the invention represents a so-called locking spring, which is shown individually in  FIG. 4 , and is provided with the reference symbol  20 . The arrangement of the locking spring on the mounting frame  50  can be seen more clearly from  FIGS. 5 and 6 . 
         [0038]    As can be seen, the locking spring  20  has a slightly curved ridge  21 , which has a horizontal orientation in later use, having a hole  22  on one end, and a guide recess  23  on the opposing end. There is a locking projection  25 , extending at an angle to the ridge  21 , which forms a pin facing downward, and initially tapers and then extends in a straight line. This projection  25  is disposed on a longitudinal side of the horizontal ridge  21 , supported from the middle, basically in the direction of the guide recess  23 . As a whole, the locking spring is formed by an appropriately stamped piece of sheet metal, which is later curved. 
         [0039]    The arrangement of the locking spring  20  on the mounting frame  50  is shown in  FIGS. 5 and 6 . In particular, it can be seen that the spring is permanently connected to the upper edge of the circumferential ridge  52  of the mounting frame  50  via the hole  22  on the corresponding end by means of a screw connection—or some other means. The ridge  21  is not, however, attached on the opposite side, but rather, merely disposed there, such that a guide projection formed on the ridge  52  of the mounting frame  50  engages in the guide recess  23 . This means that the corresponding end of the locking spring  20  can move up and down here, in the direction of the double arrow, which ultimately means that a vertical deflection of the locking projection  25  can occur. At the upper end of the guide projection  56  a height stop  57  is created by a disk secured with a screw, which delimits the potential deflection of the locking spring  20  in the upward direction, and secures it accordingly in the guide. 
         [0040]    Elements interacting with this locking spring  20  are then provided on the outer circumference, or outer surface  11  of the light fixture  10 , wherein these can be seen in particular from  FIGS. 7 and 8 . A slanted approach bevel  15 , directed outward, is used here in particular, as well as an additional stop element  17  slightly spaced apart therefrom. The spacing between the two elements is dimensioned such that at least the lower end region of the locking projection  25  of the locking spring  20  can engage in the intermediate space  18 . The two elements  15  and  17  are disposed on the outer circumference of the light fixture  10  with respect to their height such that when the spring  20  is not in the deflected state, in which the horizontal ridge  21  thus bears on the upper edge of the circumferential ridge  52  of the mounting frame  50 , the lower end region of the locking projection  25  extends into the intermediate space  18 . 
         [0041]    The interaction of the various elements can be retraced on the basis of  FIGS. 9 a    and  9   b , which show the attachment of the light fixture  10  to the mounting frame  50 . The light fixture  10  is inserted from below into the mounting frame  50  in a first step, and twisted in order to produce the bayonet joint, as described above. The bayonet joint and the arrangement of the approach bevel  15 , as well as the end stop  17  are coordinated to the one another, such that in the end state, the locking projection  25  engages in the intermediate region  18 . When twisted in the installation direction, it is ensured by the slope of the approach bevel  15  that the locking projection  25  slides along the upper surface of this bevel  15  thereby, and as a result, the spring  20  is automatically deflected upward (see  FIG. 9 a   ). As soon as the projection  25  has passed over the upper end of the approach bevel  15 , however, the springs bends, or snaps downward, and the locking projection  25  is locked in the intermediate region  18  between the approach bevel  15  and the end stop  17 . A random twisting in the unlocking direction is then blocked in this case by the approach bevel  15 . 
         [0042]    Obviously, the locking can only be released if the spring  20  is raised in a targeted manner, and the locking projection  25  is then released from the blocked position. A hole  58  is provided for this, in accordance with the illustrations in  FIGS. 10 a  and 10 b   , which extends from the undersurface of the mounting frame  50 , through the ridge  52 , to its upper edge, and opens out toward the spring  20  in a region beneath the horizontal ridge  21 , directly adjacent to the projection  25 . I.e., if a pointed tool, e.g. a paper clip or a thin screwdriver, is inserted through the hole  58 , the spring  20 , in particular the locking projection  25 , can be lifted slightly, as illustrated in  FIG. 10 b   , and the safeguard can be released. At this point, the light fixture  10  can then be twisted in the direction of the arrow in order to release the bayonet joint. The height stop  57  ensures thereby that the locking spring  20  always remains in the guide for the projection  57 , even when it is in the raised state. 
         [0043]    Ultimately, a very simple but reliable securing of the light fixture to the mounting frame is enabled by means of the measures described herein. Because a simultaneous raising of the locking spring as well as a twisting of the light fixture is necessary to release the bayonet joint, preferably only one single locking spring is actually used. This provides, however, sufficient security for preventing an unintentional releasing of the light fixture when the beam characteristic of the lamp is adjusted, e.g. through rotating the luminaire head.