A lamp (5) is secured to the end (4) of a support arm for at least horizontal translational movement, and is pivotable about a vertical axis (10) for azimuth adjustment of the light beams (from lenses 82, 83). To facilitate such horizontal movement by means of a handle (15), the handle is disposed on or adjacent the vertical pivot axis (10). The lamp, which may also be pivotable by means of the handle (15) about a horizontal axis 11, is preferably located substantially entirely on one side of the vertical axis (11).

The present invention is concerned with lamps and lamp assemblies. Whilst 
these are of particular interest for medical and dental applications, they 
may of course be used in many other situations. 
FIG. 1 shows a typical lamp assembly for a dental surgery. A support 
structure comprises an articulated two part arm on a mounting 1 (which may 
be secured to the ceiling), a pair of articulated arm sections 2, 3 and a 
bracket 4 supporting a lamp 5. The joints between these members are 
pivoted for rotation about axes 6 and 7 to permit horizontal translational 
movement of the bracket 4 in any direction, whilst the second arm 3 is 
pivoted about axes 8 and 9 and spring-balanced for vertical movement with 
a parallel ogram linkage (not shown) to maintain the bracket 4 in a 
vertical attitude. Thus the bracket and hence the lamp can be translated 
to any desired position. To permit azimuth adjustment of the lamp, the 
upper and lower ends of the bracket are pivotable relative to one another 
about a vertical axis 10. Thus this arm system permits freedom of spatial 
location together with azimuth movement of the light. This leave pitch 
movement of the light (about axis 11) to be provided within the light unit 
itself to complete the facility of universal spatial positioning combined 
with freedom to beam the light in any direction. 
Conventionally the lamp 5 is fitted with handles 14, 15. In use, the 
dentist (if right handed) will sit or stand on his patient's right and 
adjust the position and angle of the lamp by means of the right-hand 
handle 15. If he is left-handed, he will generally sit or stand on the 
opposite side and use the other handle 14. 
Although such arrangements have been found reasonably satisfactory, in 
practice they suffer from the disadvantage that, to effect movements along 
the line of arm 3, the user has to transmit the necessary forces to the 
support structure via the handle and lamp body and, in order to avoid the 
lamp simply rotating about its vertical pivot axis 10, must apply a 
compensating couple to the handle as well as the necessary directional 
force. 
According to one aspect of the present invention there is provided a lamp 
assembly with a support structure permitting translational movement of a 
lamp portion at least in a generally horizontal plane, a lamp mounted to 
the support portion so as to be pivotable about a generally vertical axis 
for azimuth adjustment of a light beam or beams from the lamp, and a 
handle secured to the lamp, the handle being disposed on or adjacent to 
the vertical pivot axis. 
In this way, the user is able to effect horizontal movement of the lamp 
without any substantial tendency for the lamp to rotate. 
A convenient arrangement is to provide that the lamp is disposed 
substantially entirely on one side of the pivot axis: the handle may then 
be disposed on the other side of the axis. 
Thus in another aspect, the invention provides an adjustable lamp 
comprising a housing rotatably attached to a bracket for rotation about a 
horizontal axis extending through the housing, a light source and beam 
forming means within the housing arranged to form a beam directed out of 
the housing transversely with respect to the said axis, and a handle 
attached to the housing for effecting the rotation thereof, the housing 
and the handle being located on opposite sides of the bracket. 
Of course, this arrangement implies a handle on only one side of the 
lamp--at least, a handle on the other side will suffer excessively from 
the disadvantage discussed above. To permit adjustment from the opposite 
side, the lamp can be made pivotable about a generally horizontal axis 
(usually desirable in any event for pitch adjustment). Then, if a 
sufficient degree of rotation of the lamp about vertical and horizontal 
axes is allowed for, it can be rotated through 180.degree. about both axes 
to assume on attitude which is a mirror-image of its former position, 
thereby permitting adjustment from the other side.

FIG. 2 shows a general perspective view of a lamp body 5 disposed on one 
side of a bracket 16, whilst a handle 15 on the other side of the bracket 
16 is secured to the lamp body 5 by a connection (described below) passing 
through a bearing in the lower part 17 of the bracket, so that, by means 
of the handle 15, the lamp body 5 can be rotated about a horizontal axis 
11, for pitch adjustment of light beams from the lamp. The upper part 18 
of the bracket forms a socket which engages the end 4 of a balanced 
support arm assembly; the end 4 including a bearing for rotation about 
vertical pivot axis 10. The support arm assembly could be as described 
above with reference to FIG. 1, or of any other suitable construction. 
The lamp housing is formed from two end mouldings 19a, 19b flanking a set 
of ribs 19c which form a ventilation grille. The mouldings are secured 
together by bolts extending between the two end mouldings 19a, 19b and 
through the ribs 19c. A front panel 20 is fixed to the housing formed by 
the end moulding and the ribs. 
The construction of the embodiment will now be described in more detail 
with reference to FIGS. 3 to 7. Referring first to FIG. 3, certain parts 
of the end 4 of the balanced support arm are shown, for clarity of 
understanding. A tubular pivot 21 carries at its lower extremity a small 
two-track slip-ring 22 which is connected to an electrical supply by an 
electrical cable 23. The small slip-ring 22 retains a tapered swivel 
sleeve 24 that is free to rotate on the tubular pivot 21 and is 
constrained from excess axial movement by a part of the arm (not shown) 
that supports the tubular pivot 21. 
The bracket 16 comprises a two piece moulded housing 25 and 26. The 
portions are shown cut away in FIG. 3. They have a joint line in the plane 
containing the axis 10 of the tubular pivot 21 and perpendicular to the 
axis 11 about which the lamp 5 rotates, these two axes being normal to 
each other. 
The upper ends of the moulded housing portions 25 and 26 have ribs which, 
when the two are fixed together, form a conical socket into which the 
tapered swivel sleeve 24 fits and where it is retained by a dowel 28 that 
has suitable locking means (not shown). 
Further ribs within the housing parts 25,26 retain a contact panel 29 that 
carries four leaf springs 30 each with a silver contact at its extremity 
and so arranged that two of these contacts press onto an inner silver 
plated track of the slip-ring 22 and the other two onto the outer such 
track. The slip-ring 22 may conveniently take the form of a 
printed-circuit disc. One conductor of the electrical cable 23 connects to 
the inner track and the other conductor to the outer track. Electrical 
current is collected by the contacts 30, one pole being passed via switch 
31 to a cable 32 while the other pole is connected to a second cable 33. 
The switch 31 may comprise a touch-sensitive on/off switch and a rotatable 
knob controlling the voltage supplied to the lamp, and therefore the 
brightness of the lamp. 
The cables 32, 33 conduct current to and from the lamp housing. The cables 
are flexible and are loosely coiled around a spacer (described below). The 
cables pass to the lamp housing from the middle of the coil. Preferably, 
there are 31/2 turns of cable in the coil. The rotation of the lamp 
housing about the axis 11 is limited to a range of 270.degree. and is 
accommodated by the cable coil tightening and loosening about the spacer. 
In an alternative embodiment, the rotation could be accommodated by using a 
second two-track slip ring transverse to the axis 11. 
FIG. 4 is a horizontal section of the lamp housing at the axis 11, when the 
output light beams are horizontal. 
The end moulding 19a of the lamp housing has a generally cylindrical 
extension 38. A cup member 42, a tubular spacer 43 and a second cup member 
44 are bolted to an integral bulkhead 40 formed by the end wall of the 
moulding 19a. The second cup member 44 has an internal serrated clutch 
surface 45, shown more clearly in FIG. 3. 
Bearing races 39 allow relative rotation of the cylindrical extension (and 
along with it the cup member 42) and the housing formed by the mouldings 
25,26. 
The flexible cables 32,33 which conduct current between the slip ring and 
the lamp housing are coiled around the spacer 43 and extend from the 
middle of the coil to the lamp housing. 
The handle 15 is moulded with a domed disc 49 and carries an axial spigot 
50 which is journelled in a tubular extension 42a of the cupped member 42. 
The spigot 50 extends through an aperture 41 in the moulding 19a. Adjacent 
the end of the spigot 50 is an annular groove 51 which is engaged by a 
notch in a lever 52 pivoted at 53, so that lever movement will retain or 
release the handle. A button headed recessed plunger 54 is incorporated 
into the handle and carries teeth 55 which can engage the serrated clutch 
surface 45 formed in the interior of the cup member 44. The teeth 55 are 
urged into engagement with the clutch surface 45 by a spring 56. Thus the 
handle 15 is normally locked to the moulding 19a but by pressing the 
plunger 54 the handle can be angularly reset to any desired relationship 
with the moulding for ease of control of the light position and 
orientation. 
A felt dust seal 57 is provided against ingress of dust into the housing 
25,26. A spring-biased lever 58 bears on the felt seal 57 to urge the seal 
against the housing portion 26, to provide frictional resistance against 
rotation of the lamp housing. 
A lamp bulb 60 is carried on a plug-in mount 62. The bulb 60 may be 
introduced into the housing through an aperture 61 in the middle of the 
front panel 20. When the bulb 60 is in position, the mount 62 closes the 
aperture and is held in position in the aperture 61 by a latch (not 
shown). The mount 62 carries two flat prong electrodes 64 which are 
electrically connected to the bulb filament. When the mount 62 is in 
position, the electrodes 64 mate with respective spring contacts 66 to 
which respective ones of the cables 32,33 are connected. A grub screw 65 
on the mount 62 sets the innermost position to which the mount 62 may be 
pushed. 
Further details of the optical system of the lamp are described below. 
The optical housing 37 is shown cut in half in FIG. 5, at the plane of the 
section of FIG. 4. The illustrated half of the housing has four main 
portions. Firstly, half of the cylindrical extension 38, terminating at 
the bulkhead 40, secondly a near mirror compartment 61a, thirdly a central 
light source compartment 63 and fourthly a far mirror compartment 61b. 
The ribs 19c form a grille in the curved "floor" of the compartments 63 
extending between the two bulkheads which separate the three compartments. 
The grille allows a cooling air flow around the light source in the 
compartment 63. 
The two mirror compartments 61a,61b each have mountings to support mirrors 
67,68 which re-direct the light beams leaving the compartments 62 so they 
converge at a point on a line which is normal to the axis 11 of rotation 
of the optical housing and which intersects this axis midway between the 
two mirrors. This intersection point is also midway between the light 
source compartment bulkheads. 
The mirrors 67,68 may be coated so as to reflect visual light but allow 
infra-red heat to pass straight through. If this is so a black metal heat 
sink would be located a short distance behind each mirror to disperse the 
heat and prevent a hot spot on the housing. 
In FIG. 5, the line along which the light beams leave the compartment 63 is 
coincident with the rotation axis 11. In FIG. 4, the line and the axis are 
shown spaced apart, but parallel. Either arrangement is practicable, but 
the arrangement of FIG. 4 has been found to facilitate balancing the lamp 
about the axis 11. 
The light source is shown in FIG. 6 and consists of a filament or discharge 
type bulb in a split reflector of the type which is the subject of our 
co-pending European patent application No. 83 307324.0 
The bulb 60 (shown schematically) is arranged so that its filament 70 lies 
at the first focus point of the two curved reflector segments 71,72 so 
that equal light beams are emitted from approximately parallel edged 
apertures 73 and 74 to converge at second focus points 75 and 76. 
As described above the bulb 60 is mounted on a mount 62 made of insulating 
material, the bulb filament being connected to a pair of prong electrodes 
64. Wires inside the mount 62 feed current to the filament 70. The 
segments 71,72 are cut away as required to allow access for the bulb and 
the mount. 
The mount 62 and the housing surfaces against which the mount locates are 
formed to ensure correct orientation of the filament and to form an 
abutment to ensure the filament is co-incident with the reflector focal 
point. For instance, non-circular integers and apertures may be used. The 
bulb 60 the reflector segments 71 and 72 and preferably the apertures 73 
and 74 are carried in a heat conducting housing which can be finned on its 
exterior for adequate heat transfer by convected air flow through the 
housing grille. 
This heat conducting housing is mounted on the housing bulkheads by two 
rectangular light tunnels aligned with the mirrors 67,68. These light 
tunnels may be closed at their extremities by glasses that diffuse the 
light and/or filter out heat from the beams. 
FIG. 7 shows a lens support member 20 which forms the front panel of the 
lamp housing. The two lenses 82,83 at the exit apertures of the housing 
are set at approx 7.degree. toe-in angle to align with the axes of the 
converging beams. These lenses may either be of a spherical type or of a 
cylindrical type and may incorporate prisms. The requirements for the 
lenses and suitable lenses are described in the applicant's copending 
application referred to above. 
The lens support member 20 is fixed on the housing by retaining screws and 
may be removed to permit cleaning of lenses 82 and 83, of mirrors 67 and 
68 and blowing off of any dust around the finned lamp/reflector housing. 
Removal of the member 80 also permits operation of the lever 52 for 
removal of the handle 15. 
The lenses 82,83 are adjustably fixed in mounts which are held in the 
member 20 by latches 84. The lens mounts may be removed to adjust the 
alignment of the lenses 82,83. 
It will be appreciated that the handle 15 used to manoeuvre and orientate 
the lamp is very close to the vertical swivel axis of the swivel sleeve 24 
and thus the greater forces required to move the articulated support arm 
can be applied almost directly to the arm and not by the usual awkward 
thumb and finger couple as is necessary when the swivel axis is located 
centrally on the lamp.