Patent Publication Number: US-11644184-B2

Title: High output micro luminary

Description:
FIELD OF THE INVENTION 
     The invention pertains to the field of recessed lighting, and in particular, to small aperture format recessed lighting with high light output. 
     BACKGROUND OF THE INVENTION 
     For high output light assemblies and luminaries, a way must be provided to dissipate heat generated in creating the light. For small aperture format light fixtures, due to the ultra-small opening through which the light is emitted into the room, the fixture requires that the heat dissipater be much larger than the opening hole in the ceiling. 
     Prior manufacturers have addressed this problem by creating a one-piece light fixture which must be cut out of the ceiling to repair or replace the fixture. 
     Therefore, what is desired is a recessed lighting fixture with an extremely small intrusion opening in the ceiling which provides a substantial amount of illumination and which allows for the LED light engine to be replaced and serviced after installation and ceiling finishing, without altering the ceiling and without the use of a large diameter trim. 
     SUMMARY OF THE INVENTION 
     In the present design a serviceable light fixture and method are provided to allow for removal and replacement of active components of the light fixture through a small opening in the ceiling having a minimal clearance with such components, without altering or damaging the ceiling and without the use of a large diameter trim. 
     The recessed light fixture is adapted for illuminating a room through a small opening in a ceiling. The light fixture can have an enclosure with a bottom, and an aperture in the bottom. A heat sink is connected to the enclosure and has a thermal interface, and the heat sink can be non-removable through the aperture. A light engine assembly is insertable and removable through the aperture, along an insertion axis. 
     The light engine assembly can have a base with a first end with an LED mounted thereto, and the base can a thermal interface adapted for thermal coupling to the thermal interface of the heat sink. The base is preferably solid or substantially solid and comprises material having high thermal conductivity suitable for effective conduction of heat from the LED to the heat sink. 
     A mechanical connector which is disposed within the enclosure and is connected to the heat sink, and is adapted to removably connect the base of the light engine assembly to the heat sink. In a connected state, the mechanical connector mechanically connects the base of the light engine assembly to the heat sink, and couples the thermal interface of the light engine assembly with the thermal interface of the heat sink, wherein the thermal interfaces of the base and heat sink are pressed together. The thermal interfaces of the base and the heat sink can be planar and, in the connected state, can be perpendicular to the insertion axis. 
     In a disconnected state, the base of the light engine assembly is mechanically dis-connected from the heat sink, and the thermal interface of the light engine assembly is de-coupled with the thermal interface of the heat sink. 
     The base of the light engine assembly is insertable through the opening in the ceiling aligned with the aperture and is operable to be selectively urged into the connected and disconnected states, from within the room, where a maximal clearance between the opening in the ceiling and the base is not substantially greater than required for the base to fit through the opening, for example where such clearance is no more than about 0.05-0.25 inches (e.g., no more than about 0.08 inch) for a 1 inch diameter opening (or 5%-25% of the diameter or corresponding dimension of the opening), and the base of the light engine assembly is removable through the opening in the ceiling, from within the room. 
     Therefore, the light engine assembly can be replaced or serviced from within the room without disturbing the ceiling, and without the use of large diameter trims. 
     The base of the light engine assembly can have a second end opposite the first end, and the thermal interface of the base can be disposed on the second end. In the connected state, the insertion axis can passes through the thermal interfaces of the base and heat sink. 
     The light engine assembly can be operable to be urged from the disconnected state into the connected state by rotation of the base relative to the heat sink in a first direction about the insertion axis, and from the connected state into the disconnected state by rotation of the base relative to the heat sink in a second direction opposite the first direction about the insertion axis. 
     The mechanical connector comprises a bayonet connector mounted to the heat sink, and the bayonet can engage the base of the light engine assembly in the connected state. 
     The recessed light fixture can include a light engine lock within the enclosure which has locked and unlocked states. In the locked state, the light engine lock is operable to prevent rotation of the base of the light engine assembly in the connected state, relative to the heat sink. In the unlock state, the light engine lock being operable to allow rotation of the base of the light engine in the connected state, relative to the heat sink, and the light engine lock is biased in the locked state. 
     The base of the light engine assembly can have upper and lower portions, with the first end of the base being on the lower portion and the second end of the base being on the upper portion. A plurality of mounting pins can extend radially outwardly from the lower portion of the base. 
     A service tool is adapted to releasably connect to the base for insertion and removal of the base through the opening in the ceiling. The service tool has a first end with a plurality of slots adapted to engage the mounting pins of the base, and the tool is adapted to rotate the base to urge the base between the connected and disconnected states. 
     The light engine lock has a cam surface, and during connection and disconnection of the base from the heat sink, the service tool is adapted to engage the cam surface of the light engine lock and to urge the light engine lock into the unlocked state. 
     The light engine assembly has a reflector module which can be in a mounted state wherein the reflector module is mounted to the lower portion of the base of the light engine assembly, and can be in a dismounted state wherein the reflector module is disconnected from the base. The reflector module is adapted to be urged from the dismounted state to the mounted state and vice versa by rotating the reflector module relative to the base about the insertion axis in a mounting direction and an opposite dismounting direction, respectively. In the mounted state, the reflector module is mounted to the base by the mounting pins of the base. 
     The reflector module can have a plurality of mounting pins extending radially outwardly, and the service tool can be adapted to releasably connect to the reflector module for insertion and removal of the reflector module through the opening in the ceiling. The first end of the tool can be adapted to engage the mounting pins of the reflector module, and to rotate the reflector module relative to the base, to urge the reflector module between the mounted and dismounted states. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view from above the ceiling of a recessed lighting fixture constructed according to a first preferred embodiment of the inventive light fixture. 
         FIG.  2    is a perspective view from below the ceiling of a recessed lighting fixture of  FIG.  1   . 
         FIG.  3    is an exploded view of the light fixture of  FIG.  1    showing the trim/diffuser assembly and the light engine assembly removed from the light fixture from below the ceiling. 
         FIG.  4    is a perspective view of the light engine assembly. 
         FIG.  5    is an exploded view of the light engine assembly. 
         FIG.  6    is an exploded view of the mechanical support and thermal components of the light fixture. 
         FIG.  7    is a perspective view of the heat dissipation assembly. 
         FIG.  8    is an exploded view showing the Ejector assembly. 
         FIG.  9    is a partial sectional view showing a version of the Wedge with integral cable. 
         FIG.  10    is a partial section view of the light fixture showing an alternate Wedge with integral cable. 
         FIG.  11    is a partial sectional view showing the Light Engine Assembly being expelled from the heat dissipation assembly and the keeper leg engaged between the two halves of the finned extrusion. 
         FIG.  12    is a side elevation view of a light engine assembly according to a second preferred embodiment of the inventive light fixture; 
         FIG.  13    is a perspective view of the light engine assembly of  FIG.  12   , from the top. 
         FIG.  14    is an exploded view of the light engine assembly of  FIG.  12   . 
         FIG.  15    is a perspective view of the second embodiment of the light fixture, from the top. 
         FIG.  16    is a side elevation view of the light fixture of  FIG.  15   . 
         FIG.  17    is a side elevation view of the light fixture of  FIG.  15   , showing the heat dissipation assembly in a lower limit position and the light engine assembly inserted. 
         FIG.  18    is a side elevation view of the light fixture of  FIG.  15   , showing the heat dissipation assembly in an elevated position. 
         FIG.  19    is a front elevation view of the light fixture of  FIG.  15   , showing the heat dissipation assembly in an elevated position. 
         FIG.  20    is a perspective view of the light fixture of  FIG.  15   , from the top, showing the heat dissipation assembly in a lower limit position. 
         FIG.  21    is a perspective view of the light fixture of  FIG.  15   , from the top, showing one half of the heat dissipation assembly in a lower limit position, with the other half removed. 
         FIG.  22    is a side elevation view of the light fixture of  FIG.  15   , showing the slide lock. 
         FIG.  23    is a perspective view of the light fixture, from the top. 
         FIG.  24    is a top view of a third preferred embodiment of the inventive light fixture with the top cover removed, and showing the heat sink assembly in the light engine access position. 
         FIG.  25 A  is a side elevation view of the heat sink assembly, of the light fixture of  FIG.  24   , with the heat sink shown in the elevated position. 
         FIG.  25 B  is a side elevation view of the heat sink assembly of the light fixture of  FIG.  24   , with the heat sink shown in the lowered, unlocked position. 
         FIG.  25 C  is a side elevation view of the heat sink assembly of the light fixture of  FIG.  24   , with the heat sink shown in the lowered, locked position. 
         FIG.  26    is a bottom view of the heat sink assembly. 
         FIG.  27    is a bottom view of the heat sink assembly, showing a light engine assembly attached to the heat sink. 
         FIG.  28    is a side view of the light engine assembly. 
         FIG.  29    is a side view of the light engine assembly in the disconnected state, and ready to be connected to or removed from the heat sink. 
         FIG.  30    is a close up view of the disconnected state of  FIG.  29   , showing the locking ring shown as translucent. 
         FIG.  31    is a side view of the light engine assembly in the connected state with the heat sink. 
         FIG.  32    is a close up view of the connected state of  FIG.  31   , showing the locking ring shown as translucent. 
         FIG.  33    is a side elevation view of light fixture, showing the heat sink in the lower position and the light engine assembly connected thereto. 
         FIG.  34    is a side cross section view of light fixture, showing the heat sink in the elevated position and the light engine assembly connected thereto. 
         FIG.  35    is a bottom view of the light fixture, showing the light engine assembly being removed through the aperture. 
         FIG.  36    is a top view of the light fixture, with the top cover removed, and showing the heat sink assembly in the wire access position. 
         FIG.  37    is a bottom view of the light fixture, showing the lighting driver being removed through the aperture. 
         FIG.  38    is a perspective view, from the top, of an embodiment of the light engine. 
         FIGS.  39 ,  40 A and  40 B  are bottom views of an embodiment of the heat sink adapted for the light engine assembly of  FIG.  38   . 
         FIG.  41    is a side view of the light engine of  FIG.  38    connected to the heat sink. 
         FIG.  42    is a side view of a modular light engine assembly embodiment of the light fixture. 
         FIG.  43    is a side view of LED module of the light engine assembly of  FIG.  42   . 
         FIG.  44    is a side view of a reflector module of the light engine assembly. 
         FIG.  45    is side view of a down-light trim module of the light fixture. 
         FIG.  46    is a side view of a service tool for connecting the modules of the light engine assembly. 
         FIG.  47    is side view of the service tool connected to the LED module. 
         FIG.  48    is a side, cross-section view of the service tool connecting the LED module to the heat sink. 
         FIG.  49    is a side view of the service tool connected to the reflector module. 
         FIG.  50    is a side view of the service tool connecting the reflector module to the LED module. 
         FIG.  51    is a side view of the downlight trim module positioned for connection to the light fixture. 
         FIG.  52    is a side cross-section view of the modular light engine assembly installed in the light fixture. 
         FIG.  53    is a side view of the connection tool removing the trim module. 
         FIG.  54    is side view of an embodiment of the heat sink. 
         FIG.  55    is a side view of the heat sink of  FIG.  54   , in the lowered position, and with a light engine assembly connected thereto. 
         FIG.  56    is side view of the assembly of  FIG.  55    in the lowered position, with the light engine assembly disposed below the ceiling. 
         FIG.  57    is a side view as in  FIG.  56   , with the LED accessible for servicing. 
         FIG.  58    is top view of a fourth preferred embodiment of the inventive light fixture. 
         FIGS.  59  and  60    are each a side cross section view of the light fixture of  FIG.  58   . 
         FIG.  61 - 64    are bottom images (inverted) of the light fixture of  FIG.  58   , showing an embodiment of the locking mechanism. 
         FIG.  65    is an exploded view of a fifth preferred embodiment of the inventive light fixture. 
         FIG.  66 A  is a front elevation view of the light fixture of  FIG.  65   . 
         FIG.  66 B  is a side elevation view of the light fixture of  FIG.  65   . 
         FIG.  66 C  is a bottom view of the light fixture of  FIG.  65   . 
         FIG.  67    is a perspective view of a sixth preferred embodiment of the inventive light fixture. 
         FIG.  68    is an exploded view of the light fixture of  FIG.  67   . 
         FIG.  69    is a perspective view of a seventh preferred embodiment of the inventive light fixture. 
         FIG.  70    is an exploded view of the light fixture of  FIG.  69   . 
         FIG.  71    is a perspective view of a eighth preferred embodiment of the inventive light fixture. 
         FIG.  72    is an exploded view of the light fixture of  FIG.  71   . 
         FIG.  73    is a perspective view of a ninth preferred embodiment of the inventive light fixture, from the bottom, showing the cable retractor in the retracted position. 
         FIG.  74    is a perspective view of light fixture of  FIG.  73   , from the bottom, showing the cable retractor in the extended position. 
         FIG.  75    is a side cross-sectional view of a tenth preferred embodiment of the inventive light fixture. 
         FIG.  76    is a side cross-sectional view of an eleventh preferred embodiment of the inventive light fixture. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     Referring to  FIGS.  1 - 5   , the recessed light fixture is adapted to be installed above a ceiling or other surface and to project light into a room below, through an opening in the ceiling, which is typically, but not necessarily, a circular opening. 
     The light fixture can include a trim/diffuser assembly  1  and a light engine assembly  2 . The light engine assembly  2  can be substantially cylindrical with a generally circular cross section and include a thermal gap filling pad  3 , a light engine power connector  4 , a light engine housing  5 , a reflector  6 , a LED support  7 , a LED module  8 , and an electrical connection  9  to connect the LED module to the light engine power connector  4 . 
     Referring to  FIGS.  6 - 7   , the light fixture can also include a power input module  10 , a heat dissipation assembly  11 , a chassis  12 , a pair of hanger bars  13 , and a docking module and power input  14 . 
     The heat dissipation assembly  11  can include a finned heat exchanger  15  with an opening in a center sized and shaped to closely receive the light engine assembly  2  therein and the opening can expand to receive the light engine assembly. Preferably, the finned heat exchanger  15  includes a compression spring  16  which biases the opening in a contracted position but which allows the opening to expand to receive the light engine assembly  2  into the opening. The finned heat exchanger  15  can include two halves connected by the compression spring  16  such that the two halves can separate slightly against the bias of the spring to enlarge the opening to receive the light engine assembly  2 . The two halves of finned heat exchanger  15  can separate in a horizontal direction perpendicular to a vertical axis of insertion of the light engine assembly into the opening of the heat dissipation assembly. 
     A thermal interface area  17  surrounds the opening in the finned heat exchanger  15  and is adapted to thermally couple with the thermal gap filling pad  3  of the light engine assembly  2 . 
     The bias of the compression spring  16  maintains a thermal couple and mechanical/friction couple between the heat dissipation assembly  11  and the light engine assembly  2  to provide both a thermal connection with and a mechanical support of the light engine assembly  2 . 
     The heat dissipation assembly  11  can also include a light engine assembly ejector  18  which is operable to eject the light engine assembly  2 . The ejector assembly  18  is spring biased  21  downwardly and, when the light engine assembly  2  is installed, the ejector assembly  18  is urged upwardly by the light engine assembly  2  and exerts a downward force on upwardly extending legs  24  of the Light Engine Assembly  2  to help expel the sub-assembly from the ceiling. Specifically, downwardly extending ejector legs  19  of the ejector assembly  18  contact and exert force on the upwardly extending legs  24  of the light engine assembly  2 . 
     To remove the light engine assembly  2 , the two halves of the Heat Dissipation Assembly  11 , are separated via a wedge  22  (and/or  23 ) that is urged between the two halves of the heat dissipation assembly by pulling down on a cable  22 ′/ 23 ′ connected to the wedge, which cable is accessible from below the ceiling (e.g., from within the room). This causes the wedge to slide between and separate the two finned heat exchanger halves. As the wedge separates the two halves of the finned heat exchanger  15 , the light engine assembly  2  is at least partially ejected downwardly from the assembly by the ejector assembly  18  which moves downwardly, and a keeper leg  20  of the light engine ejector assembly  18  is thereby positioned between the two halves of the finned heat exchanger  18 , The keeper leg  20  is operable to hold the heat dissipation assembly open until the light engine assembly is fully re-inserted into the heat dissipation assembly. When the light engine assembly  2  is inserted back into the heat dissipation assembly, the light engine assembly  2  pushes the wedge back into a relaxed position wherein it is not separating the halves of the heat dissipation assembly. The light engine assembly also urges the ejector assembly  18  upwardly which displaces the keeper leg  20  from between the halves of the heat dissipation assembly, which allows the compression spring  16  to close the heat dissipation assembly onto the light engine assembly  2  as discussed above. 
     The light engine assembly  2  can include one or more fins  25  extending upwardly from a top portion. The fin(s)  25  are operable to dissipate heat and are also operable to properly align the power input module  10  so that the light engine power connector  4  makes a proper connection to a complementary socket on the bottom of the power input module  10 . As shown, the fins  25  can be angled generally upwardly and radially outward away from the docking module  14  so that they are operable to urge the power input module  10  toward the docking module  14  if required. 
     Referring to  FIG.  3   , the trim/diffuser assembly  1  and the light engine assembly  2  are removed through the opening in the ceiling material. The light engine assembly  2  provides the electrical connection to power the LED&#39;s, the thermal gap filling pad  3  to provide an interface to the heat dissipation assembly  11  and a thermally conductive (e.g. aluminum) light engine housing  5  that conducts the heat from the LED&#39;s and transfers it to the heat dissipation assembly  11  through the thermal pad  3 . 
     The light engine assembly  2  also includes the high-performance reflector  6 , the LED light engine module  8 , the light engine support/holder  7  and the electrical interconnect  9 . The light engine assembly  2  is responsible for providing the highest output light level and light quality based on the input power being supplied to the assembly. Therefore, the reflector, diffuser and trim are specifically designed to provide the optimum light for each LED Light Engine. 
     The heat dissipation assembly  11  and chassis  12  are installed prior to ceiling installation and remain above the ceiling, fastened to the joists that support the ceiling. The light engine assembly  2  is captured by the two halves of the fined heat exchanger  15  which are spring loaded to close around the outer diameter of the light engine assembly  2 , when the light engine assembly  2  is fully inserted into the finned heat exchanger  15 . This spring-loaded assembly provides pressure on the thermal pad  3  to insure optimal heat transfer. The electrical connection for the light engine assembly  2  is completed during the insertion process of the light engine assembly  2  insuring a proper electrical connection after assembly. 
     The power input module  10  can also be removed through the same hole in the ceiling by rotating the pivoting power module dock  14  90 degrees vertically so that the power input module  10  can be removed vertically downwardly out of the hole in the ceiling. 
     The light engine assembly  2  is insertable through the opening in the ceiling aligned with the aperture and is operable to be selectively urged into connected and disconnected states, from within the room, where a maximal clearance between the opening in the ceiling and the light engine assembly is not substantially greater than required for the light engine assembly to fit through the opening, for example where such clearance is no more than about 0.05-0.25 inches (e.g., no more than about 0.08 inch) for a 1 inch diameter opening (or 5%-25% of the diameter or corresponding dimension of the opening), and the light engine assembly  2  is removable through the opening in the ceiling, from within the room. In this manner, the light engine assembly can be replaced or serviced from within the room without disturbing the ceiling. 
     Referring to  FIGS.  12 - 23   , in second preferred embodiment of the recessed light fixture, the light fixture can include a light engine assembly  102  with a trim/diffuser assembly  101 , a light engine lower housing  105 , a light engine upper housing  107 , a thermal gap filling pad  103 , a light engine power connector  104 , an LED module  108 , an electrical connection  109  to connect the LED module to the light engine power connector  104 , a reflector  106 , and a diffuser  106 ′. 
     The light fixture can also include a power input module  110 , a heat dissipation assembly  111 , a chassis  112 , a pair of hanger bars (not shown). 
     The heat dissipation assembly  111  can include a finned heat exchanger  115  with a preferably circular opening in a center, which is sized and shaped to closely receive the (e.g., tubular) light engine assembly  102  therein and which can expand to receive the light engine assembly. Preferably, the finned heat exchanger  115  includes a spring  116  which biases the opening in a contracted state but which allows the opening to expand to selectively receive the light engine assembly  102  into the opening. The finned heat exchanger  115  can include two halves connected by the spring  116  such that the two halves can separate slightly against the bias of the spring to enlarge the opening to receive the light engine assembly  102 . The two halves of finned heat exchanger  115  can separate in a horizontal direction perpendicular to a vertical axis of insertion of the light engine assembly into the opening of the heat dissipation assembly. For example, one half of the finned heat exchanger  115  can pivot in a horizontal plane relative to the other half to allow expansion and contraction of the opening. 
     The heat dissipation assembly  111  includes a thermal interface area  117  that surrounds the opening in the finned heat exchanger  115  and is adapted to thermally couple with the thermal gap filling pad  103  of the light engine assembly  102 . 
     The bias of the spring  116  maintains a thermal couple and mechanical/friction couple between the heat dissipation assembly  111  and the light engine assembly  102  to provide both a thermal connection and a mechanical support of the light engine assembly  102 . 
     The light engine assembly  102  is inserted into and removed from the light fixture from within the room, through the opening in the ceiling material. The light engine assembly  102  provides the electrical connection to power the LED&#39;s, the thermal gap filling pad  103  provides an interface to the heat dissipation assembly  111  and a thermally conductive (e.g. aluminum) upper light engine housing  107  conducts the heat from the LED&#39;s and transfers it to the heat dissipation assembly  111  through the thermal pad  103 . 
     The heat dissipation assembly  111  and chassis  112  are installed prior to ceiling installation and remain above the ceiling, fastened to the joists that support the ceiling, or other support structure. The light engine assembly  102  is captured by the two halves of the fined heat exchanger  115  which are spring loaded to close around the outer diameter of the light engine assembly  102 , when the light engine assembly  102  is inserted into the finned heat exchanger  115 . This spring-loaded assembly provides pressure on the thermal pad  103  to insure optimal heat transfer. The electrical connection for the light engine assembly  102  is completed during the insertion process of the light engine assembly  102  insuring a proper electrical connection after assembly. 
     The heat dissipation assembly  111  is slidably mounted to a pair of guide post  130 ,  132  connected to and projecting vertically upwardly from the chassis  112  such that the heat dissipation assembly  111  can move vertically relative to the chassis (and ceiling)—guided by the guide posts—from a lower limit position (See  FIG.  17   ) to a number of elevated positions (See  FIGS.  18 - 19   ). A first half of the heat dissipation assembly  111  has a pair of holes  134 ,  136  and each one of the guide posts  130 ,  132  extends through an associated one of the holes. Thus, the heat dissipation assembly  111  is confined to move only vertically relative to the chassis  112 , except that the second half can also move laterally (e.g., horizontally pivoting) away from the first half to allow insertion and removal of the light engine assembly. 
     The light engine assembly  102  is insertable into the heat dissipation assembly  111  when the heat dissipation assembly  111  is in the lower limit position. In this position, the opening in the heat dissipation assembly  111  is in the expanded state and is operable to receive the light engine assembly  102  therein. When the light engine assembly  102  is fully inserted into heat dissipation assembly  111 , the power connector  104  makes electrical connection to the power input module  110  to provide a power path to the light engine assembly  102 . 
     Pushing further upwardly on the light engine assembly  102  causes the light engine assembly  102  and heat dissipation assembly  111  to move upwardly from the lower limit position. As the heat dissipation assembly  111  moves upwardly from the lower limit position, the opening contracts around the light engine assembly  102  to make a thermal and mechanical coupling with the engine assembly  102 . The light engine assembly  102  can be pushed further upward until the trim element  101  (or a lower flange thereof) is flush with the ceiling lower surface. Preferably, the range of movement of the light engine assembly  102  and heat dissipation assembly  111  relative to the chassis  112  from the lower limit position to a maximal elevated position is preferably at least about 1 inch, and is preferably at least sufficient to accommodate a range of ceiling thicknesses, for example ⅜ inch to 1 inch thick. 
     To remove or replace the light engine assembly  102  from the light fixture, a downward pulling force is applied to the light engine assembly  102  from within the room, to pull the light engine assembly  102  and heat dissipation assembly  111  downward from the elevated position to the lower limit position. Downward movement of the heat dissipation assembly  111  into the lower limit position causes the heat dissipation assembly  111  to contact a wedge  140  fixed to the chassis  112  which causes the two halves of the heat dissipation assembly  111  to separate against the bias of the spring  116 , thereby expanding the opening and releasing the light engine assembly  102 . 
     To assist in the downward movement, the light engine assembly  102  can include a pair of opposed wings  142  which extend laterally (radially) outwardly from the body which abut horizontal surfaces of the opposed halves of the heat dissipation assembly  111  such that a downward force can be exerted on the heat dissipation assembly  111  as the heat dissipation assembly  111  opens up while approaching the lower limit position as described above. The wings  142  can be formed as part of a printed circuit board interconnecting the power connector  104  and electrical connection  109 , or another component of the light engine assembly. 
     To maintain the light engine assembly  102  in a desired elevated position (i.e., flush with the ceiling), the heat dissipation assembly  111  can include a pair of automatic slide locks  150 ,  152  which engage the guide posts  103 ,  132  to maintain the heat dissipation assembly  111  in the desired elevated position. Preferably the slide locks allow manual vertical movement of the heat dissipation assembly  111  and light engine assembly  102  but are sufficient to resist the force of gravity such that the heat dissipation assembly  111  and light engine assembly  102  maintain a desired, fixed elevated position when at rest. 
     Each slide lock can include a base portion  160  which is slidably mounted to one of the guide posts  130 ,  132 . The heat dissipation assembly  111  is supported by the base of the slide lock via a coil spring  146  disposed around the associated guide post such that the heat dissipation assembly  111  can move a certain distance downwardly relative to the slide lock. The slide lock can include a lever  144  which is pivotally connected to the base portion and includes an opening through which the associated guide post extends. The lever  144  is adapted to allow upward movement of the heat dissipation assembly  111  relative to the associated guide post and is adapted to prevent downward movement of the heat dissipation assembly  111  when in a locked state, by engaging the guide post. The lever  144  is biased in an upwardly pivoted (locked) state by a lever spring (not shown). The lever  144  includes a release tab  148  extending therefrom which is engaged by the heat dissipation assembly  111  during lowering to disengage the slide lock. 
     In operation, when the heat dissipation assembly  111  is moved upwardly into an elevated position as described above, the heat dissipation assembly  111  pushes each slide lock upwardly (e.g., via the base) and when a desired position is reached, the biased lever  144  engages the guide post to prevent downward movement of the heat dissipation assembly  111 . To lower the heat dissipation assembly  111 , a downward force is applied to the heat dissipation assembly  111  which moves downward relative to each slide lock by compressing the coil spring  146  until the heat dissipation assembly  111  contacts the release tab  148  which causes the lever  144  to pivot downward against the bias of the lever spring resulting in disengagement (unlocking) of the slide lock to allow the heat dissipation assembly  111  to move further downward to the lower limit position. Preferably, the slide lock, when unlocked, provides little to no resistance to downward movement of the heat dissipation assembly  111 ; and provides little to no resistance to upward movement at all times. 
     As above, the light engine assembly  102  is insertable through the opening in the ceiling aligned with the aperture and is operable to be selectively urged into connected and disconnected states, from within the room, where a maximal clearance between the opening in the ceiling and the light engine assembly  102  is not substantially greater than required for the light engine assembly to fit through the opening, for example where such clearance is no more than about 0.05-00.25 inches (e.g., no more than about 0.08 inch) for a 1 inch diameter opening (or 5%-25% of the diameter or corresponding dimension of the opening), and the light engine assembly  102  is removable through the opening in the ceiling, from within the room. In this manner, the light engine assembly  201  can be replaced or serviced from within the room without disturbing the ceiling. 
     Referring to  FIGS.  24 - 37    an embodiment of the light fixture  200  has an enclosure  202  with a top (not shown), side walls  205 , and a bottom wall  204  with an aperture  206  therethrough ( FIGS.  35  &amp;  37   ), of for example a diameter of about 1 inch or more. The enclosure  202  is adapted to be fastened to support structure above a ceiling structure  272  (for example via hanger bars), and remains above the ceiling. 
     The light fixture  200  includes a light engine assembly  208  ( FIG.  28   ), which can include an LED module  210 , a reflector  212  ( FIG.  34   ) and a trim element  214 . The LED module  210  can have a base  216  with a lower portion  211  having a lower surface  218  (normally downwardly facing), and with an upper portion  217  having an upper surface  220  (normally upwardly facing). An electrical connector  223  can be connected to the LED  222  by wires and is operable to releasably connect to the lighting driver  274  to power the LED. The light engine assembly  208  is adapted to be removed from the enclosure  202  through the aperture  206  of the enclosure  202  and the opening  273  in the ceiling  272 , from within the room, without removing the enclosure  202  and without disturbing the ceiling. 
     At least one LED  222  ( FIG.  27   ) (for example a 6 mm chip-on-board (COB) LED) can be mounted to the lower surface  218  of the base  216 , and is operable to emit light through the light engine assembly  208  and into the room. The trim element  214  can be connected to the base  216 , such as by one or more screws  215 , and preferably surrounds the lower portion  211  of the base  216  and LED  222 . The reflector  212  can be disposed within the trim element, around the LED  222 . 
     Portions of the lower and upper surfaces  218 ,  220  of the base  216  form lower and upper thermal interfaces  224 ,  226 , which are preferably substantially planar; however, the thermal interfaces can be stepped with several portions which on different planes. The upper portion  217  of the base  216  can be substantially cylindrical in shape, with a substantially circular cross section and with the upper surface  220  (and thermal interface  226  thereof) being substantially circular. For a light fixture configured for about a 1 inch diameter ceiling opening, for example, a maximal outside diameter of the upper portion  217  of the base  216  can be about 0.96 inches and the surface area of the upper thermal interface  226  can be about 0.72 square inches (π*(diameter squared)/4). For such an application, the base  216  can have a height of about 0.9 inches between the upper and lower surfaces thereof. 
     The base  216  of the LED module  210  is preferably adapted and operable to effectively conduct heat generated by the LED  222  from the lower thermal interface  224  to the upper interface  226 . The base  216  can be solid (or at least substantially solid) and can include (or consist or consist essentially of) one or more materials having high thermally conductivity, such aluminum or copper, or another suitable metal or alloy, or non-metallic material. 
     The light fixture  200  can also include a heat sink  228  which has a preferably planar thermal interface  230  ( FIG.  26   ) which is configured for thermal connection with the upper thermal interface  226  of the base  216  of the LED module  210 , and which is aligned with and disposed over the aperture  206  of the enclosure  202 . The heat sink  228  has a plurality of fins  231  which are integrally form with and/or thermally connected to the thermal interface  230 , such that the heat sink  228  is adapted and operable to receive heat generated by the LED  222  through the thermal interface  230  and to dissipate such heat to ambient air through the fins  231 . As depicted, the fins  231  can project laterally (horizontally) radially outwardly from a main body of the heat sink. The heat sink  228  is preferably larger than the aperture  206  of the enclosure  202  and is not removable through the aperture  206 . Therefor, the heat sink  228  preferably remains within the enclosure  202  (and above the ceiling  272 ) during servicing of the light engine assembly  208  as described herein. 
     The heat sink  228  is a component of a heat sink assembly  232  which includes a frame  234  having a base  236 , a top  238  and a plurality of legs  240  (for example three legs) interconnecting the base and top  236 ,  238 . The base  236  of the frame  234  includes an aperture  242  through which the light engine assembly  208  is received, as discussed below. 
     Referring to  FIGS.  25 A and  25 B , the heat sink  228  is preferably movably mounted within the frame  234  such that the heat sink  228  can move, for example, vertically (parallel to a Z axis) relative to the frame, between an elevated limit position ( FIG.  25 A ) and a lowered limit position ( FIG.  25 B ). The heat sink  228  can be slidably mounted on a plurality of (e.g., three) guide posts  244  disposed within the frame  234  which are vertically oriented and are located around the periphery of the heat sink  228 . The periphery of the heat sink  228  can include a plurality of channels  246 , each vertically oriented and sized and shaped to slidably receive and confine one of the guide posts  244 . As depicted, the guide posts  224  can be cylindrical in shape and the channels  246  can have a complementary tubular (or partially tubular) shape, sized to closely (but slidably) confine the guide posts. 
     Preferably, the heat sink  228  is biased in the elevated limit position, which can be effected by, for example, compression springs  248 , disposed around the guide posts  244  between the base  236  of the frame  234  and the heat sink  228 , and preferably contacting the associated channel  246  of the heat sink  228 . Preferably, the springs  248  are in compression (or at rest) when the heat sink  228  is in the elevated position ( FIG.  25 A ) such that the heat sink  228  is biased toward the elevated position. 
     As described further below, the heat sink  228  can preferably rotate relative to the frame  234  about the vertical axis (Z axis) between a lowered unlocked position ( FIG.  25 B ) and a lowered locked position ( FIG.  25 C ). Preferably, the guide posts  244  are confined between, but are not connected to, the base  236  and top  238  of the frame  234 , and the legs  240  thereof, such that the sub-assembly of the heat sink  228  and guide posts  244  can rotate within and relative to the frame  234  about the vertical axis (Z axis) a predetermined amount. 
     Each leg  240  of the frame  234  preferably includes a guide slot  250  having vertical portion  252  connected, at a bottom thereof, to a horizontal portion  254 . The horizontal portion  254  of at least one guide slot  250  includes a locking projection  256  extending vertically downwardly at or adjacent the junction of the horizontal and vertical portions. 
     The heat sink assembly  232  can include a plurality of radially outwardly projecting guide tabs  260  each of which extend through an associated one of the guide slots  250  in the legs  240  of the frame  234  to guide the vertical and rotational movement of the heat sink  228  relative to the frame  234 . The projecting guide tabs  260  can be part of a bottom plate  258  which is integral or connected to a bottom of the heat sink  228 . The bottom plate  258  of the heat sink can include an aperture  259  which is aligned with the aperture  242  of the base  236  of the heat sink assembly  232 , and through which the light engine assembly  208  is received. 
     During vertical movement of the heat sink  228 , between the elevated position and the lowered position, each guide tab  260  moves within and is guided by the vertical portion  252  of the associated guide slot  250  of a guide post  240 . During rotational movement of the heat sink  228  between the lowered unlocked position ( FIG.  25 B ) the lowered locked position ( FIG.  25 C ), each guide tab  260  moves within and is guided and limited by the horizontal portion  254  of the associated guide slot  250 . A vertical height of each horizontal portion  254  is less than a corresponding vertical height of the associated guide tab  260  such that, when the guide tab is in the lowered locked position, guide tab  260  is urged upward by the aforementioned upward bias of the heat sink  228  due to compression springs  248 , such that the heat sink  228  is prevented from moving into the lowered unlocked position, by the locking projection  256 . To move the heat sink  228  into the lowered, unlocked position, the heat sink is urged downwardly against the upward bias until the guide tab  260  is below the locking projection  256 , and then the heat sink  228  can be rotated such that the guide tab  260  moves past the locking projection  256  and into the vertical portion  252  of the guide slot  250 . At this point the upward bias will urge the heat sink  228  into the elevated position. 
     Referring to  FIGS.  26 - 32   , the heat sink  228  includes a bayonet connector  262  which is disposed within the enclosure  202  and is operable for releasably mounting the light engine assembly  208  to the heat sink with a twisting motion about an insertion axis A, from within the room.  FIG.  26    shows a locking ring  264  of the bayonet connector  262 , which is ring-shaped and is disposed around the thermal interface  230  of the heat sink  228 . The locking ring  264  can move vertically (Z axis) relative to the main body of the heat sink  228 . The vertical movement of the locking ring  264  is guided and limited by guide screws  267  which are directed through the locking ring and into the body of the heat sink  228  and which prevent rotational movement of the locking ring  264  relative to the heat sink  228 . The locking ring  264  is biased toward the main body of the heat sink  228 , by a plurality of compression springs  266  disposed around the guide screws  267  below the locking ring  264 . 
     The locking ring  264  has a plurality of (for example, three) locking tabs  268  which project horizontally radially inwardly from an inner circumference of the locking ring, and which are configured to engage with an associated one of an equal number of bayonet slots  270  ( FIG.  28   ) in the upper portion  217  of the base  216  of the light engine assembly  208 . Each bayonet slot  270  of the base  216  has an opening on the upper surface  220  of the base  216  which is configured to receive an associated locking tab  268  of the locking ring  264  and has a channel which extends partially around a periphery of the upper portion  217  of the base below the upper surface  220  thereof, and which communicates with the opening of the slot. 
       FIGS.  29  and  30    are side views of the light engine assembly  208  in a disconnected state, ready to be connected to, or removed from, the heat sink  228 .  FIG.  30    is a close up view of the disconnected state of  FIG.  29   , showing a locking ring  264  of the bayonet connector  262  as translucent.  FIGS.  31  and  32    are side views of the light engine assembly  210  in a connected state with the heat sink  228 .  FIG.  32    is a close up view of the connected state of  FIG.  30   , showing a locking ring  264  of the bayonet connector  262  as translucent. 
     Referring to  FIG.  33   , when the heat sink  228  is in the lowered, locked position ( FIGS.  33  and  25 C ), the trim element  214  extends below the ceiling  272  and can be grasped by hand. In this position, the light engine assembly  208  can be connected and disconnected to the heat sink  228 . To connect the light engine assembly  208  to the heat sink, the electrical connector  223  of the light engine assembly  208  can be connected to a complementary electrical connector connected to the lighting driver  274  and extending through the opening  273  of the ceiling  272  (e.g., as shown in  FIG.  47   ), then the light engine assembly  208  can be inserted axially vertically upwardly along the insertion axis A through the opening  273  in the ceiling  272  and through the aperture  206  of the enclosure until the upper thermal interface  226  of the base  216  contacts the thermal interface  230  of the heat sink  228 . At this point, the light engine assembly  208  is in the disconnected state ( FIGS.  29  &amp;  30   ). Then, the light engine assembly  208  can be urged into the connected state ( FIGS.  31  &amp;  32   ) by manually rotating the light engine assembly  208  by the trim element  214 , for example by about 30-40 degrees in a first rotational direction, about the vertical insertion axis A, which is preferably in a clockwise direction as viewed from within the room. The insertion axis A can be an optical axis of the LED  222  and/or of the light engine assembly, which can be parallel to a vertical (Z) axis. When the light engine assembly  208  is in the connected state (and when transitioning between the connected and disconnected states) the insertion axis A preferably passes through centers of, and is perpendicular to, the thermal interfaces  216 ,  230 . 
     When the light engine assembly  208  is in the connected state ( FIGS.  31  &amp;  32   ), it can be urged into the disconnected state ( FIGS.  29  &amp;  30   ) by rotating the light engine assembly  208  by the same amount, but in an opposite rotational direction about the insertion axis A, for example in a counter-clockwise as viewed from the room. When in the disconnected state, the light engine assembly  208  can be removed axially vertically downwardly along the insertion axis A through the aperture  206  of the enclosure and the opening  237  of the ceiling  272 . In this manner, the light engine assembly  208  can be readily serviced from within the room, without disturbing the ceiling and without the use of large radius trims. 
     Referring to  FIG.  34   , when the light engine assembly  208  is in the connected state with the heat sink  228 , the heat sink  228  can be moved into the lowered unlocked position and then into the elevated position. The upward bias urges the light engine assembly  208  upward until a radial flange  217  of the trim  214  contacts the room-side of the ceiling structure  272 , around the opening  273 . As can be appreciated, the variable upward bias of the heat sink  228  allows the light fixture  200  to adapt to ceiling materials of various thickness and various fixture installation heights relative to the ceiling. 
     When the light engine assembly  208  is in the connected state, the locking ring  264  of the bayonet connector  226  is displaced downwardly (away from the heat sink  228 ) against the upward bias which mechanically secures the light engine assembly  208  to the heat sink  228 , and in addition pushes the light engine assembly  208 , and particularly the base  216  thereof, against the heat sink  228  which causes the upper thermal interface  226  of the base  216  to press against the thermal interface  230  of the heat sink  228  which creates an efficient and effective thermal connection between the upper thermal interface  226  of the base  216  of the LED module  210  and the thermal interface  230  of the heat sink  228 . This allows the light fixture to use high-output LEDs, while effectively dissipating the heat generated thereby. For example the light fixture can use LEDs providing about 900-1000 lumens delivered into the room and at, for example about 9-15 watts, all serviceable through a small ceiling opening of, for example, a diameter of 1 inch. 
     The axial insertion and rotational connection process, from within the room, provided by the configuration and operation of the light engine assembly  208  and bayonet connector  262  allow the light engine  208 , and in particular the LED module  210  and base  216  thereof, to be axially inserted through and removed from an extremely small opening  273  in the ceiling  272 , and particularly where the opening  273  is minimally larger than, and has minimal clearance around, the outer diameter of the light engine assembly  208 . For example, for a light fixture configured for about a 1 inch diameter ceiling opening, a maximal outside diameter of the upper portion  217  of the base  216  can be up to about 0.96 inches, providing a minimal clearance of about 0.04 inches (e.g., no more than about 0.05 or 0.08 inches) between the opening  273  of the ceiling  272  and the base  216  of the light engine assembly  208 . Furthermore, because the opening  273  in the ceiling  272  is only minimally larger than the diameter of the light engine assembly  208 , the radial flange  217  of the trim element  214  can be correspondingly small. It can be appreciated that the dimensions of the light engine assembly  208  can change; however, the minimal clearance provided between the opening  273  in the ceiling  272  and the light engine assembly  208  can remain minimal and substantially constant, while maintaining serviceability of the light fixture from within the room, without disturbing the ceiling. 
     Referring to  FIGS.  26  and  27   , the heat sink assembly  232  can include a light engine lock  233  adapted to only allow disconnection of the light engine assembly  208  from the heat sink  228  when the heat sink  228  is in the lowered locked position. The light engine lock  233  can be pivotally connected to the base  236  of the heat sink assembly  232  and can include a free end  235  which is received within and engages a complementary locking recess  237  in the base  216  of the LED module  210  to prevent rotational movement thereof, when the light engine lock is in a locked state. The light engine lock  233  is in a locked state ( FIG.  27   ) when the heat sink  228  is not in the lowered, locked position. The light engine lock  233  is in a unlocked state ( FIG.  26   ) when the heat sink  228  is in the lowered, locked position. In the unlocked state, the free end  235  of the light engine lock  233  is retracted from the locking recess  237  in the base  216  of the LED module  210 , thereby allowing rotation of the LED module. The light engine lock  233  can be spring biased in the locked position and can be urged into the unlocked position by contacting a portion of the base  236  of the frame  234  of the heat sink assembly  232  during rotation of the heat sink  228  into the lowered, locked position. 
     Referring to  FIGS.  24  and  35 - 37   , the heat sink assembly  232  can preferably move along the bottom  204  of the enclosure  202  to allow selective removal of the light engine assembly  208  and the lighting driver, or the electrical connections for a remote driver  274 . The base  236  of the frame  234  of the heat sink assembly  232  can be pivotally connected to the bottom  204  of the enclosure  202  by, for example a fastener  276 . In a light engine access position ( FIGS.  24  and  35   ), the thermal interface  230  of the heat sink  228 , the aperture  259  of the bottom plate  258  of the heat sink  228  and the aperture  242  of the base  236  of the frame  234  are aligned with the aperture  206  of the bottom  204  of the enclosure  202  to allow insertion (connection) or removal (disconnection) of the light engine assembly  208  to/from the heat sink  228  through such aperture  206 , from within the room. In a wire access position ( FIGS.  36  and  37   ), the lighting driver  274  is aligned with the aperture  206  of the bottom  204  of the enclosure  202  to allow insertion or replacement of the lighting driver, or the electrical connections for a remote driver  274  through the aperture  206 , from within the room. 
     Referring to  FIGS.  38 - 41   , an embodiment of the heat sink  328  can have a rotating electrical connection ring  380  which can be disposed at least partially radially inwardly from the locking ring  264  of the bayonet connector  262  and at least partially around the thermal interface  230  of heat sink  328 . The ring  380  can be formed of, or can include a printed circuit board (PCB). The ring  380  can be configured to rotate relative to the main body of the heat sink  328  about the insertion axis A, during rotational connection and disconnection of the light engine assembly  308 , as described above. The electrical connection ring  380  can be disposed within a ring-shaped channel  231  recessed in the main body of the heat sink  328  and surrounding the thermal interface  230  thereof, and can be substantially confined to limited rotational movement about the insertion axis A. 
     The light engine assembly  308  can include upwardly extending keying and rotating tabs  382  which are received within and interface with complementary keying features  384  of the ring  380  to cause complimentary rotation of the ring  380  during connection and disconnection of the light engine assembly  308 . 
     The light engine assembly  308  can also include electrical connections  386  connected to the LED  222  which interface with electrical connections  388 ,  390  of the ring  380 . The electrical connections  388 ,  390  of the ring  380  can be connected to a power source, such as lighting driver  274 , by wires  392 . The ability of the ring  380  to rotate with the light engine assembly  308  provides for substantially solely normal/perpendicular axial/non-sliding electrical closing and opening operations (as opposed to lateral/sliding movements) which reduces the area required for the electrical connections  388 ,  390  and avoids problems associated with sliding electrical connections. In addition, this configuration avoids a separate electrical connection step for the light engine assembly  308 . The act of connecting the light engine assembly  308  to the heat sink  328  with the bayonet connector  262  completes, in one step, the electrical connection, in addition to the mechanical and thermal connections described above. 
     Referring to  FIGS.  42 - 53   , an embodiment of the light engine assembly  408  can be composed of modular parts which can include an LED module  410 , a reflector module  412 , and a trim module  414 . The LED module  410  can have a base  416  with an upper portion  417  having a configuration and functionality similar to the corresponding structure described above, including that of base  216 . The LED module  410  can have an LED  422  connected thereto, as described above. The LED module  410  can be removably connected to, and removable from, the heat sink  228 , with, for example, the bayonet connector  226 , in the manner described above. 
     The LED module  410  can include a pair of opposed mounting pins  427  which extend horizontally radially outwardly (perpendicular to the insertion axis A) from the lower portion  411  of the base  416  thereof. The reflector module  412  can be removably connected to the LED module  410  by, for example, a bayonet connection. The reflector module  412  can have a pair of bayonet slots  428  which engage the mounting pins  427  of the LED module  410 . The bayonet slots  428  of the reflector module  412  can have an upwardly-facing vertical opening adapted to receive an associated mounting pin  427  and can have a horizontal channel connected to the opening and adapted to confine the mounting pin. The reflector module  412  is mounted to the LED module by first moving the reflector module  412  axially vertically, along the insertion axis A, to contact the LED module  410  and receive the mounting pins  427  into the openings of the bayonet slots  428 , and then rotating the reflector module  412  about the insertion axis, for example clockwise as viewed from the room. The reflector module  412  can be detached from the LED module  410  with a reverse process. Each bayonet slot  428  can include a detent  431  between the opening and the horizontal channel thereof and operable to resist passage of the associated mounting pin  427  of the LED module  410 , to temporarily secure the reflector module  412  to the service tool  420  during connection and disconnection of the reflector module  412 . The reflector module  412  can include a pair of opposed mounting pins  429  which extend horizontally radially outwardly therefrom. 
     The trim module  414  can be removably connected to the enclosure  202 , such as to aperture plate  418  ( FIG.  52   ), depending downwardly from the enclosure  202 . The trim module  414  can have a resilient, snap-fit or friction connector for removable connection. 
     Referring to  FIGS.  46 - 53   , the light fixture  200  having the modular light engine assembly  410  can include a service tool  420  for mounting and removing the modules. The service tool  420  can have a first end  422  adapted to be inserted axially vertically through the opening  273  of the ceiling  272  and into the aperture  206  of the enclosure  202  from within the room, to rotate the modules to connect and disconnect modules to the heat sink, as described above. The first end  422  of the service tool  420  can be substantially tubular and adapted to separately receive at least lower portions of the LED module  410  and reflector module  412  therein. The first end  422  can have a pair of opposed, inverted T-slots  430  having an opening communicating with an edge of first end  422 . The T-slots are adapted to selectively engage the mounting pins  427 ,  429  of the LED module  412  and reflector module  414  for mounting and removal of the modules. 
       FIGS.  47 - 51    show the sequence of installing the modular light engine assembly  408  using the service tool  420 . First,  FIG.  47    shows the LED module  410  connected to the service tool  420  and ready for axial insertion through the opening  273  of the ceiling  272 .  FIG.  48    shows the LED module  410  in position to be rotated by the service tool  410  for connection to, or disconnection from, the heat sink  228 . Then,  FIG.  49    shows the reflector module  412  connected to the service tool  420  and ready for axially insertion through the opening  273  of the ceiling  272 .  FIG.  50    shows the reflector module  412  in position to be rotated by the service tool  410  for connection to, or disconnection from, the (installed) LED module  410 . Then,  FIG.  51    shows the trim module  414  ready for manual connection to the light fixture.  FIG.  52    shows all modules installed and connected to the light fixture. The sequence for removing the modules is the reverse process. 
     Referring to  FIGS.  46  &amp;  53   , the tool  420  can have a second end  424  adapted to engage a radially-outwardly extending flange  426  of the trim module  414  to assist in removal of the trim module  414 . 
     Referring to  FIGS.  54 - 57   , an embodiment of heat sink  528  can include an elongated arm  532 , extending downwardly from, and preferably formed integrally with, the main body of the heat sink  528 . The arm  532  can have a free end  534  having a similar configuration, and performing the same function as, the lower portion  211 ,  411  of the base  216 ,  416  of the LED module  210 ,  410  described above, including having a lower surface  518  supporting an LED  222 , conducting heat from such LED to the body of the heat sink  528 , and supporting the reflector element/module  212 ,  412  and trim element/module  214 ,  414 . 
     When the heat sink  528  is in the elevated position for operation, the arm  532  is entirely retracted within the enclosure  202 , preferably wherein the lower surface  518  supporting the LED  222  is in a position corresponding to the position of the lower portion  211 ,  411  of LED module  210 ,  410 , and lower surface  218 ,  418  thereof, when in the elevated position. 
     When the heat sink  528  is in the lowered position as described above, the arm  532  extends through the various apertures described herein and through the ceiling structure  272  for servicing. A longitudinal axis L (parallel to Z axis) of the arm  532  is aligned with such apertures, and a length of the arm  532  is configured such that the free end  534  extends through the aperture  206  of the enclosure  202  and through the opening  273  of the ceiling  272 , when the heat sink  528  is in the lowered position ( FIGS.  55 - 57   ). Preferably an electrical connector  536  is provided on the free end  534  of the arm  532 , and is accessible from the room, for connecting and disconnecting the LED  222  from the power source. In this position, free end  534  of the arm  532  and the lower surface  518  thereof (and LED  222  attached thereto) are disposed below the ceiling  227 , such that the trim element  214 ,  414 , and the LED  222  can be removed and replaced from within the room, for servicing, without disturbing the ceiling structure. 
     Referring to  FIGS.  58 - 60   , an embodiment of the light fixture  600  can have a heat sink  628  having fins  631  projecting from a top surface and having a relatively low vertical profile (i.e., low height, e.g., 1-2 inches). The heat sink  628  can be fixed relative to the enclosure  602  for example within the enclosure, or above the enclosure  602  and optionally thereby forming a top of the enclosure. A light engine assembly  408 , for example having a structure as described above, can be connected to a bottom of the heat sink  628  in the manner described above, including through the opening  273  in the ceiling structure  272  and the aperture  606  of the enclosure  602 , from within the room, for example by using the service tool  420  to connect the light engine assembly  408  to the bayonet connector  262  mounted to the heat sink  628 , within the enclosure  602 . 
     The aperture  606  of the enclosure  602  can be located on a bottom wall  604  of the enclosure. As described above, the thermal interface  630  of the heat sink  628  can be aligned with the aperture  606 , and can be recessed upwardly from the bottom of the heat sink  628  to assist in the proper location, and to guide the rotation, of the base  416  of the LED module  410  during mounting and dismounting of the LED module  10 . 
     Referring to  FIGS.  61 - 64   , an embodiment of the light engine lock  633  is operable to lock the LED module  410  in the bayonet connector  262  when in the LED module  410  is in the connected state, and is adapted to be actuated by the service tool  420 . The light engine lock  633  can be connected to a bottom of the heat sink  628  adjacent and radially outwardly from the bayonet connector  262 . The light engine lock  633  can have a locking projection  634  which extends radially inwardly toward and is received within and engages a locking recess  636  on a periphery of the LED module  410  to prevent rotation thereof, when the LED module  410  is in the connected state and when the lock  633  is in a locked position. The lock  633  can be biased in the locked position ( FIGS.  61 ,  63 ,  64   ), for example by a spring  638 . The light engine lock  633  can have an inclined cam surface  640  extending away from the heat sink  628  and radially outwardly from the LED module  410 . As shown in  FIG.  62   , when the service tool  420  is connected to the LED module  410  attached to the bayonet connector  262 , the first end  422  of the service tool  420  contacts the cam surface  640  of the lock  633  and urges the lock  633  radially outward against the bias, and into an unlocked position, wherein the locking projection  634  of the lock  633  is displaced from the locking recess  636  of LED module  410  such that the LED module  410  can be rotated and removed from the bayonet connector  262 , using the service tool  420 . Preferably, the light engine lock  633  does not engage or limit rotation of the reflector module  412  relative to the LED module  410 , when the lock  633  is in the locked or unlocked positions. The reflector module  412  can include a recess  642  on a periphery thereof configured to avoid contact with the locking projection  634  and cam surface  640  of the lock such that the reflector module  412  can rotate when the lock  633  is in the locked state, for connection and removal of the reflector module  312  independent of the LED module, including when using the service tool  420 . 
     Referring to  FIGS.  65  and  66 A -C, in another preferred embodiment of the light fixture, the light engine assembly is composed of modular parts including an LED module  710 , a reflector module  712 , and a trim module  714 , as described herein regarding light engine assembly  408 . Heat sink  728  has a plurality of fins  731 . The light fixture has an enclosure  702  (without a top), side walls  705 , and a bottom wall  704  with an aperture  706  therethrough of, for example, a diameter of about 1 inch or more. In accordance with the present invention, the light fixture is serviceable from the room without the need to remove the ceiling material. In addition, LED module  710  includes a removable heat sink that provides for efficient thermal coupling to permanent heat sink  728  of the fixture. When installed and in operation, the combination of the removable heat sink in LED module  710  coupled with permanent heat sink  728  allows for optimal thermal management, providing high quality light over the lifetime of the fixture. For example, a preferred embodiment of the fixture provides 475-1500 Lumens of delivered light through a 1-inch ceiling aperture (with a ¾ inch lens aperture) with only 7-15 watts of power. Reflector module  712  is field-changeable, parabolic and is capable of creating a soft, symmetric beam pattern (with narrow to wide beam spreads by simply swapping out the reflector from the room below). Trim module  714  also provides glare control (e.g., UGR&lt;1, not measurable). 
     Referring to  FIGS.  67 - 72   , in other preferred embodiments of the light fixture, the light fixture can include a light engine assembly  802  with a trim module  814  (which may have a radially-outwardly extending flange  826 ), spring connectors  878  (or spring-tab connectors  879 ), a light engine lower housing  805 , a light engine upper housing  807 , and a heat sink  828 . The light fixture can further include an LED module  808 , a reflector  806 , a diffuser  806 ′ (and may also include a lens  806 ″), and a reflector module  812  (which may have a wall wash trim  813 ). 
     Referring to  FIGS.  73 - 74   , in another preferred embodiment, the light fixture  600  can include a cable retractor  902  which is operable to retract a power line  904  for the LED module  410  during installation to prevent the power line  904  from interfering with the installation. 
     The power line  904  preferably includes a main power line  906  (or wiring harness), which can be connected to a power source or lighting driver. The power line  904  also includes an LED power cable  908  which is connected to the LED. The main power cable  906  and the LED power cable  908  are releasably connectable together such that the LED module  410  can be replaced if required, through the aperture, as described herein. Preferably the main power line  906  and the LED power cable  908  include modular connectors  910 ,  912  adapted to releasably electrically and mechanically interconnect. 
     The main lower line  906  can include a fixed section  932  which is fixed relative to the enclosure for example by one or more clamps  934  or the like, and can include a free section  936  which is connected to the LED power cable  908 . 
     The cable retractor  902  can include a biasing element  914 , such as a coil spring (not shown), and a retractor cable  916  connected to the biasing element. The biasing element  914  is preferably substantially laterally (e.g., horizontally) offset from the LED module  410  when mounted such that it is operable to bias (pull) the retractor cable  916  into a retracted position laterally offset from the LED module  410  during mounting. The LED Module  410  can include a leash  920  which is preferably fixedly connected to the LED Module and releasably connectable to the retractor cable  916 . 
     The light fixture  600  also preferably includes a retractor cable guide  918  connected to the light fixture and disposed between the biasing element  914  and the LED module  410  when mounted, and more preferably disposed adjacent the LED module. The retractor cable  916  (and preferably the power line  904 ) pass through an opening or passage of, and/or are guided by, the retractor cable guide  918 , which is operable to limit downward movement of portions of the retractor cable  916  and leash  920  that are located between the biasing element  914  and the cable guide  918  during installation and removal. As shown, the retractor cable guide  918  can be in the form of a bridge connected to the light fixture  200  through which the retractor cable  916  and power cable  904  pass. 
     Preferably, the cable guide  918  is located and operable to prevent the retractor cable  916  (under tension from the biasing element  914  of the cable retractor  902 ) from substantially contacting or binding against an outer edge of the opening  273  in the ceiling and/or aperture  206  in the enclosure  202  during installation and removal of the LED module  410 . The cable guide  918  is preferably configured to guide the retractor cable  916  and the leash  920  connected thereto, substantially parallel to the insertion axis during installation and removal of the LED module  410 . For example, the cable guide  918  can include a bearing portion  938  against which the retractor cable  916  bears (e.g., slides) during installation and removal of the LED module  410 , and the bearing portion  938  can be substantially aligned with (e.g., substantially vertically above or slightly radially outwardly from) an outer edge of the opening  273  in the ceiling and/or aperture  606  of the enclosure  602 . The cable guide  918  is preferably configured to guide the power line  904  in a similar manner, although the power line  904  is preferably not under tension. 
     The retractor cable  916  is preferably connected to the modular connector  910  of the main power line  906 , and the retractor cable  916  can include a releasable connector  924  between the biasing element  914  and the module connector  910  of the main power line  906 . The leash  920  of the LED Module  410  is preferably releasably connectable to the retractor cable  916  by a releasable connector  922 , such as a pull chain type connector, or other suitable releasable connector. 
     Preferably, the retractor cable  916  and leash  920  are configured such that the LED power cable  908  is substantially slack (i.e., not in any substantial tension) when the leash  920  is connected to the retractor cable  916  and the LED power cable  908  is connected to the main power line  906 , including when the power line  904  is in a retracted or extended state. For example, the taut length of the leash  920  plus the retractor cable  916  (between the leash and the modular connector  910 ) is preferably greater than the length of the LED power cable  908  such that the LED power cable remails substantially slack during installation and removal, while the retractor cable  916  is in tension. 
     The light fixture  200  can also include a retrieval line  926  which can be used to retrieve the main power line  906  in the event that the leash  920  is disconnected from the retractor cable  916  and the main power line  906  is disconnected from the LED power cable  908  and is retracted. The retrieval line  926  has a first end  928  which is connected to the light fixture adjacent to the LED module  410  and which can be accessed through the aperture, for example with a hook tool. A second end  930  of the retrieval line  926  is connected to modular connector  910  of the main power line  906  and/or the retractor cable  916 . The retrieval line  926  is preferably configured to pass through the retractor cable guide  918 . When needed, the retrieval line  926  can be engaged by a tool and pulled through the aperture to retrieve the main power line  906   
     Referring to  FIG.  75   , in another preferred embodiment of the light fixture  600 , to increase the contact area of the thermal interfaces (and thereby increase the rate and/or efficiency of heat transfer), a base  1016  of an LED module  1010  can have a convex upper portion  1011  and the heat sink  1028  can have a recess  1029  having a complementary concave shape configure to closely receive the base  1016  of the LED module  1010  such that the base makes an effective mechanical and thermal connection with the heat sink  1028 . Alternatively, the convex/concave configuration of the base and heat sink can be reversed such that the upper portion  1011  of the base can have a concave recess which is configured to couple with a convex portion of the heat sink  1028 . 
     Preferably, in each configuration, the thermal interfaces of the base and heat sink are configured to press together and thermally couple when in the connected state and are operable to relatively rotate under such pressure such that the light engine assembly can be urged between and into the connected and disconnected states as described herein. As an example, the convex upper portion  1011  of the base  1010  (or in the alternative configuration, the convex portion of the heat sink  1028 ) can have a contiguous or non-contiguous surface of revolution about the insertion axis A such as a shape which is substantially conical, frustoconical, semi-spherical, or semi-ellipsoidal (along a major axis of the ellipsoid), or another suitable shape, and the recess  1029  of the heat sink  1028  (or base  1010  in the alternative) can have a complementary contiguous or non-contiguous shape that together are suitable to permit such relatively rotation under such pressure. 
     Referring to  FIG.  76   , in another preferred embodiment, the light fixture  200  can include a driver enclosure  2000  connected to the (main) enclosure  2002  for housing an integrated driver.