Note: Descriptions are shown in the official language in which they were submitted.
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A LIGHTING FIXTURE
The present invention relates to a lighting fixture for projecting a beam of
light and for
use for spot lighting in connection with theater stages, cinema and television
studios
and the like, the fixture comprising:
- a light source arranged at one end of a housing having a light beam exit
aperture
at the opposite end thereof, the light source and aperture being arranged
generally concentric with a longitudinal or optical axis of the lighting
fixture,
- light beam influencing means at least comprising one or more, preferably
four,
beam-shaping blades and preferably also comprising other light influencing
means such as one or more lenses and/or an iris and/or a pattern or gobo, for
influencing a light beam emitted by the light source and being arranged along
the
path of the light beam along said longitudinal axis through the housing from
the
light source to the aperture, and
- adjustment means for adjusting the position of at least said one or more
beam-
shaping blades and preferably of all said influencing means relative to said
longitudinal axis.
The purpose of a lighting fixture as defined above is to produce a well-
defined light
beam or light cone with a geometry, angle of conicity and focal point that may
be
altered manually or by remote control. A lighting fixture will normally
comprise a light
source, a reflector, a beam-shaping gate with beam-shaping blades, a pattern
or gobo,
an iris, a focusing lens, a zoom lens and a color filter as well as a
suspension structure
allowing the lighting fixture to be pivoted vertically and horizontally.
The visible part of the light emitted by the light source is collected by the
reflector and
is sent towards the iris, the gobo and the beam-shaping gate as a parallel
light beam.
The infrared part of the radiation from the light source passes through the
dichroic
coating of the reflector and impinges on the inner surface of the housing
surrounding
the light source, the heat being transported to the outer surface of the
housing having
cooling ribs for emitting the heat to the surrounding atmosphere.
It is often necessary to be able to determine the geometry of the light beam
and this is
achieved by means of the zoom lens varying the angle of conicity of the light
cone and
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by shaping or cutting off the periphery of the light beam by means of the beam-
shaping gate with beam-shaping blades so as to obtain geometrical figures such
as
squares, triangles, trapezes etc. The lenses project the light out through the
aperture
of the housing opposite the light source and through the color filter at the
front end of
the lighting fixture. It is important that the different elements influencing
the shape and
other characteristics of the light beam function as precisely as possible even
when
being influenced by the heat radiated from the light source and not removed by
means
of the dichroic reflector. This entails that the location and the
configuration of the
adjustment means for the beam-shaping blades, the gobo and iris are such that
any
bending caused by the heat influence from the light beam be kept at a minimum.
Lighting fixtures of this type are often arranged in places where it is
difficuit to access
them manually and it is therefore of great importance that the adjustment
means for
adjusting the above-mentioned beam influencing means be as easily accessed and
as
flexible as possible when manual operation of the adjustment means is
required.
US Patent NO. 5,345,371 discloses a lighting fixture of the type in reference
where the
four beam-shaping blades or shutters are slidingly insertable in slots from
outside, the
shutters being radially adjustable by gripping a holder for each shutter and
sliding the
shutter in or realtive to the optical axis. The shutters may also be tilted
manually to a
certain extent. However, a further tilting possibility is acieved by allowing
the portion of
the fixture containing the shutters to be rotated as a unit around the axis.
Thus is a
complicated solution and needs manual acces to all holders of the shutters as
well as
manipulation of the rotation means for rotating part of the fixture.
Motorisation for
remote control of this design will be very complicated and costly.
US Patent No. 4,890,208 discloses a lighting fixture of the type in reference
where four
shutters are arranged for motorized displacement radially towards the optical
axis and
motorized tilting by means of rack and pinion mechanisms. This solution is
complicated and has only limited tilting capability, i.e. displacement
capability
circumferentially around the axis. Furthermore this solution is not weel
suited for
manual operation.
It is an object of the invention to provide a lighting fixture of the type
indicated, wherein
access for manual operation is convenient and not dependent on the orientation
of the
lighting fixture, wherein motorization for remote control may be established
in a simple
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and reliable manner and wherein the range of displacement circumferentially
around
the optical axis is as great as possible.
According to the invention this object is achieved by at least the adjustment
means
corresponding to said one or more beam-shaping blades and preferably all the
adjustment means are arranged for rotation around said longitudinal axis and
are
connected to a respective influencing means such that rotation of the
adjustment
means around said longitudinal axis adjusts the position of the respective
influencing
means relative to said longitudinal axis.
Hereby the adjustment means may be accessed from practically any angle and no
limit to the adjustment possibilities in circumferential direction are
inherent.
In the currently preferred embodiment the adjustment means comprise an annular
body arranged with the axis thereof substantially coinciding with said
longitudinal axis.
This is a particularly simple and effective embodiment.
In the currently preferred emmodiment of the invention the annular body
comprises an
outer rim for being engaged for applying rotative force thereto, the surface
of said
outer rim being provided with friction enhancing means such as roughening
means,
rubber surfacing, projections or teeth. Hereby manual and remote operation of
the
adjustment means is particularly simple and efficient.
Advantageously, the fixture further comprises one or more electrical motors
connected
to a respective drive wheel engaging said outer rim of a respective annular
body for
applying rotative force thereto, and preferably the drive wheel is a gear and
the
respective outer rim engaged by a respective gear is provided with teeth for
meshing
with the teeth of said gear when said gear rotates.
For use in remote control of the lighting fixture with pre-determined
positions of the
light influencing means it is advantageous that the annular body be provided
with a
position indicating means for indicating the angular position of the annular
body
relative to said longitudinal axis. Hereby a reference point for the remote
control
operation is available thereby eliminating errors and inaccuracies.
Advantageously, the position indicating means comprises an element that may be
remotely sensed such as a magnet or a gap, and the fixture further comprises
remote
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sensing means for sensing the angular position of said
element relative to said longitudinal axis.
So as to obtain the greatest flexibility of
adjustment and the greatest range of adjustment, the
adjustment means for each of the one or more beam-shaping
blades comprises radial adjustment means for adjusting the
position of the blade radially relative to said axis and
circumferential adjustment means for adjusting the position
of said blade circumferentially around said axis.
A particularly simple and efficient as well as
accurate embodiment of the light fixture according to the
invention is provided by the adjustment means for each of
the one or more beam-shaping blades comprising two adjacent
co-centrical annular bodies or rings each connected to one
point of the blade such that relative rotation of the two
rings alters the radial position of the blade.
In the currently preferred embodiment, the rings
comprise guiding tracks recessed into the lateral surface of
each ring facing the other ring, and each blade comprises a
body extending generally transversely to said axis and two
arms extending generally parallel to said axis, the arms
each being provided with sliding connecting means for
connecting the respective arm to each of the rings and being
adapted for being slidingly received in a guiding track in
each of said rings.
In accordance with this invention, there is
provided a lighting fixture for projecting a beam of light
and for use for spot lighting in connection with theater
stages, cinema and television studios and the like, the
fixture comprising: a light source arranged at one end of a
housing having a light beam exit aperture at the opposite
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end thereof, the light source and aperture being arranged
generally concentric with a longitudinal or optical axis of
the housing; light beam influencing means comprising at
least one beam-shaping blade that is adjustable to shape the
periphery of a light beam emitted by the light source so as
to form the light beam into a selected one of a plurality of
geometric shapes, and a light influencing element selected
from the group consisting of a lens, an iris, and a pattern
or gobo, for influencing a light beam emitted by the light
source and being arranged along the path of the light beam
along said longitudinal axis through the housing from the
light source to the aperture; and adjustment means
operatively associated with each beam-shaping blade for
adjusting the position of its associated beam-shaping blade
relative to said longitudinal axis, each adjustment means
comprising an annular body arranged with the axis thereof
substantially coinciding with the longitudinal axis, and
being arranged for rotation around said longitudinal axis
and being connected to its associated beam-shaping blade
such that rotation of the adjustment means around said
longitudinal axis adjusts the position of the associated
beam-shaping blade relative to said longitudinal axis.
In the following the invention will be explained
more in detail in connection with preferred embodiments of a
lighting fixture according to the invention described solely
by way of example with reference to the accompanying
drawings, where:
Fig. 1 is an isometric elevational view of a
lighting fixture according to the invention for manual
operation,
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Fig. 2 is a partially cut-away view of the
lighting fixture in Fig. 1 illustrating the internal
configuration of the lighting fixture,
Fig. 3 is a schematic cross-sectional view of the
lighting fixture of Figs. 1 and 2, the cross-section being
taken along a vertical plane containing the longitudinal or
optical axis of the lighting fixture,
Fig. 4 is an enlarged scale view of the left-hand
part of Fig. 3,
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Fig. 5 is an isometric elevational view of the bottom half of the frame of the
lighting
fixture of Figs. 1 and 2,
Fig. 6 is an exploded view of the beam-shaping blades and adjustment rings of
the
fixture in Figs. 1 and 2,
5 Fig. 7 is an axial end view of the blades and rings shown in Fig. 6 in
nested assembled
condition,
Figs. 8 and 9 are schematic axial end views corresponding to Fig. 7
illustrating the
adjustment of the beam-shaping blades of Figs. 6-7,
Fig. 10 is an illustration of the constructive principles of the guiding
tracks in the
adjustment rings for the beam-shaping blades,
Fig. 11 schematically illustrates an alternative embodiment of the beam-
shaping
blades and the adjustment mechanisms therefor,
Fig. 12 shows an isometric partly exploded view in larger scale of the
position
adjustment mechanism for the lenses shown in Fig. 2,
Fig. 13 shows an enlarged view of a detail of the construction shown in Fig.
12.
Referring now to Figs 1-5, a lighting fixture 1 according to the invention is
suspended
in a suspension fitting 2 having an aperture 3 for fixing the fitting 2
pivotably to a not
shown support structure in a theater, a television studio or the like. The
fitting 2 is
pivotably attached to the body of the lighting fixture 1 at 4, the attachment
point being
adjustable by sliding the pivot attachment point 4 in a slit 5 in a frame 6 so
as to
compensate for change of balance because of insertion or removal of different
elements in the lighting fixture 1.
The lighting fixture 1 may thus be manually pivoted around two mutually
substantially
orthogonal axes allowing the direction of a light beam emitted by the fixture
to be any
desired direction.
If it is desired to be able to remotely control the direction of the beam, the
pivoting
action may be achieved by means of remotely controlled electrical motors in
many
different ways that will be obvious to those skilled in the art.
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The frame 6 is generally U-shaped having two arms supporting the body of the
lighting
fixture I between said arms. A series of toothed rims 7-18 are arranged for
rotation
around a longitudinal or optical axis 19 (see Fig. 3). The teeth of the
toothed rims are
configured such that the teeth of a pinion of a drive unit may engage and mesh
there-
with if the light beam influencing facilities of the lighting fixture operated
by rotation of
the bodies 7-18 are to be motorized for remote control.
In the manually operated embodiment shown in Figs 1-4, the teeth of the
toothed rims
serve as a roughening element of the surface of the rim of each of the annular
bodies
7-18 such that good frictional engagement between the fingers of a hand and
the
toothed rims or annular bodies 7-18 may be achieved for rotating the annular
bodies 7-
18 manually.
Such roughening of the rim surface may be achieved in many other ways such as
scoring of the surface or coating with rubber or provision of small
projections etc.
In such case and if motorization of the rotation of the bodies 7-18 is
desired, then a
'frictional surface engagement of for instance the surface of a rubber coated
drive
wheel driven by an electrical motor with the roughened rim surface may be
provided
for instead of the meshing of the teeth of a pinion with teeth of the rim of
the annular
body.
A light source or lamp 20 emits a light beam composed of individual light
beams such
as illustrated at 20a, the visual portion thereof being reflected by a
dichroic reflector 21
through a focusing lens 22 and a zoom lens 23 and out of the lighting fixture
through
an aperture 24 in the housing 25 of the fixture 1, the light beam 20a
travelling through
a not shown color filter arranged in four color filter holders 26 that may be
pivoted
around pivots 27 so as to allow a color filter to be inserted and removed in
the holders
26 in any of four directions determined by the four holders 26. Hereby the
color filter
may be inserted and removed from the best angle for manual access for a given
orientation of the housing 25. The entire light beam projected by the lighting
fixture is
of course composed of a plurality of light beams analogous to individual light
beam
20a.
The infra red portion of the light beam 20a is transmitted through the
dichroic reflector
21 to cooling ribs 22 in a manner well known in the art so as to reduce the
heat
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distortion of elements arranged along the path of the light beam from the
light source
20 to the exit aperture 24.
These elements comprise an iris 28 connected to the annular body 7, a pattern
or
gobo 29 connected to the annular body 8, four beam-shaping blades 30, 31, 32
and 33
connected to the pairs of annular bodies, 9 -10, 11-12, 13 -14 and 15 -16,
respectively, the focusing lens 22 connected to the annular body 17, and the
zoom
lens 23 connected to the annular body 18.
The annular bodies or rings 7-18 are connected in different manners to the
respective
light beam influencing elements 22, 23 and 28-33 so that the position of these
elements may be altered relative to the axis 19, and thus the light beam, by
rotating
the rings around said axis. The individual connections between the individual
rings and
the respective elements will be described more in detail in the following.
The feature of being able to alter the position of the light influencing
elements and
particularly of the light beam shaping blades 30-33 by means of rotating the
corresponding rings allows the position alteration to be carried out manually
from a
convenient angle of approach for a given orientation of the housing 25. As the
rim
surface of each of the rings 7-18 may be engaged manually at most of the
extent of
the circumference thereof, the manual adjustment of the position of a
respective light
beam influencing element may be performed from the most convenient angle of
approach to the housing 25. Furthermore, the manual adjustment may be carried
out
with one hand which is important as the fixture is often located such that
access with
both hands is difficult and perhaps impossible.
Hereby the lighting fixture according to the invention does not have the
disadvantages
of known lighting fixtures where the adjustment means for adjusting the
position of a
light beam shaping blade may be very inconveniently located relative to the
position of
the person operating the lighting fixture so that the person for instance has
to reach
around the lighting fixture housing to access the adjustment means thereby
risking
being burned on the hot housing surface and rendering rapid and precise
position
adjustment difficult and perhaps impossible.
This advantage can also be obtained by rotative means other than rings with a
rim
surface for being engaged manually or mechanically. Elements having a
plurality of
radially extending spokes spaced circumferentially for being engaged at the
ends
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thereof by fingers of a hand or a motorized driving means may also be used. A
circumferentially disposed endless belt arranged for substantially circular
movement
around the longitudinal axis may also be utilized instead of the illustrated
rings. All
means allowing access along a major part of the circumference of the housing
and
rotative frictional engagement by fingers or a motorized drive unit may be
used to
allow such convenient access to the adjustment means for altering the position
of the
beam influencing elements.
The feature of altering the position of the light influencing elements by
rotative means
also entails simple and reliable establishment of a certain adjustment setting
of a
respective influencing means such that pre-programmed settings may be set up
for
certain lighting requirements knowing that it will be simple, quick and
reliable to
achieve such settings either manually or remotely under difficult conditions,
for
instance during the course of a theater show where adjustments in the dark are
necessary.
A further advantage is obtained by the shown structure according to the
invention in
that the construction is such that no light is emitted from the interior of
the fixture
except through the aperture 24, and all adjustments of the light beam
influencing
elements may be carried out without creating a light emission slit or
aperture. Hereby,
the disadvantage of all known lighting fixtures that light "leaks" therefrom
is eliminated
which is of great value, particularly for theater use.
Referring again to Figs. 1- 5, the frame 6 is constituted by two identical
halves 6a and
6b abutting each other at 6c. The rings or annular bodies 7-18 are rotatably
and
slidingly supported in annular grooves 34 in annular support rings 35 by means
of
annular projections or ridges 36 slidingly received in the annular grooves 34.
The
support rings 35 are each constituted by half a ring fixedly attached to or
made in one
piece with one half of the frame 6, for instance 6a (see Fig. 1). In other
words each of
the frame halves 6a and 6b is fixedly attached to or integral with a series of
half rings
as shown in Fig. 5, where the bottom half 6b of the frame 6 is shown with the
corresponding half rings 35.
30 When assembling the lighting fixture 1, the adjustment rings 7-18 with
corresponding
beam influencing elements 22, 23 and 28-33 are arranged in the bottom half 6b
of the
frame with corresponding half rings 35 such that the ridge 36 of each
adjustment ring
is received in the corresponding groove 34 of the respective half ring 35 of
the bottom
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frame half 6b. Thereafter the top half 6a of the frame 6 with corresponding
half rings
35 is placed abutting the bottom half 6b at 6c such that the ridge 36 of each
adjustment ring is received in the corresponding groove 34 of the respective
half ring
35 of the top frame half 6a. The adjustment rings 7-18 will thus be slidingly
and
rotatively supported along the entire cicumference thereof by the
corrresponding rings
35.
Each of the adjustment rings or annular bodies 7-18 may then be rotated
manually or
by means of suitable mechanical means by applying a tangential force to the
rim of the
respective adjustment ring whereby the ridge 36 thereof slides in the
respective
annular groove 34 of the respective support ring 35. The material of the
ridges 36 and
the grooves 34 are chosen such that frictional sliding resistance is kept at a
minimum.
The support rings 35 may be made of cast aluminium, and the adjustment rings
may
be made of glass-fiber reinforced plastic. The ridges 36 are made of a low
frictional
material such as teflon, a ring of said material being embedded in the lateral
surface of
the corresponding adjustment ring. Hereby the frictional sliding resistance
between
the low friction material and the cast aluminium will be low, and the
adjustment rings
may consequently be rotated by applying a relatively small tangential force to
the rim
thereof.
Each of the adjustment ring pairs 9/10, 11/12, 13/14 and 15/16 carries a
respective
light beam shaping blade 33, 32, 31 and 30, respectively, by means of pairs of
arms
33a,b, 32a,b, 31a,b and 30a,b, respectively, held by the adjustment ring pairs
in a
manner described more in detail below. So that the two rings of each ring pair
can
rotate relative to one another, a low friction material ring 37 is arranged
between each
pair of adjustment rings as illustrated in Figs. 4 and 6.
Referring now to Figs. 4 and 6-9, the arrangement of the four light beam
shaping
blades 30-33 will now be explained more in detail.
The blades 30-33 are nested as illustrated in Figs. 4, 6 and 7, each blade 30-
33 being
carried by a pair of opposed arms, 30a-33a and 30b-33b, respectively.
It is important that the blades 30-33 are located as axially close to each
other as
possible so as to achieve a sharp cut-off boundary of the light beam all
around the
cicumference thereof which only can be achieved if the blades are arranged
such that
there is no substantial distance between them in the axial direction of the
housing.
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This is particularly well illustrated in Figs. 3 and 4 where it is evident
that the spacing
of the blades in the direction of the axis 19 is slight.
The arrangement shown also has the advantage that the axial distance between
the
beam-shaping blades 30-33 and the iris 28 as well as the gobo or pattern 29 is
small
5 so that a good sharpness or quality of the influence of the blades, the iris
and the
gobo on the light beam may be obtained simultaneously because of the small
axial
distance covered by all said elements.
The blades 30-33 are shaped as shown in Figs. 6-8 having a generally
elliptical planar
body 38 with an aperture 39 having a periphery comprising a curved portion 40
and
10 linear portions 41, 42 and 43, said periphery serving as the beam cut-off
edge of the
blade body 38. This is illustrated in Fig. 7 where the peripheries of the
apertures 39 of
the four bodies 38 of the blades 30-33 define the periphery of the beam
shaping
aperture 44. A multitude of different shapes of the aperture 44 may be
achieved by a
combination of a rotation of the different blades 30-33 around the axis 19
with a
displacement of said blades 30-33 radially relative to said axis 19.
The radial displacement of the individual blades 30-33 is illustrated in Figs.
8-9 where
the periphery portion 42 of blade 33 is shown in Fig. 8 at the maximum radial
distance
from the axis 19 and in Fig. 9 at the minimum radial distance from said axis
19. The
rotational displacement is achieved by rotating the ring pair 9/10 carrying
the blade 33
around the axis 19. Combinations of the radial and the rotational displacement
of each
blade allows the creation of a great variety of peripheral shapes of the
aperture 44.
The elliptical shape of the 39 has been chosen to give a relative stiff blade
as well as a
continuous and smooth outer perimeter of the body. Hereby it is avoided that
the
bodies of the blades interfere with one another when they are displaced
relative to one
another even though the axial spacing of the bodies is small. So as to avoid
such
mutual interference between the bodies as well as between the pairs of arms
30a,b-
33a,b it is advantageous that the radial displacement of the bodies take place
in shuc
a manner that practically no flexing of the arms takles place during such
displacement,
i.e. that the distance between the ends of the arms of each pair is constant
during
such radial displacement and that no torsional forces are exerted on the arms
during
such radial displacement.
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In the currently preferred embodiment of the invention shown in Figs. 1-9,
this is
achieved as follows.
Each arm is provided with an angled end portion 45 having a guiding pin 46
extending
therethrough and projecting from both opposed surfaces of the angled portion
45. The
plane of each end portion 45 is substantially parallel to the plane of the
body 38 of the
respective blade.
The rings of each pair of rings, for instance 15 and 16 in Fig. 6 or 9 and 10
in Fig. 8-9
are identical and one lateral surface of each ring is provided with a recessed
circumferentially extending track 47 in the bottom of an annular
circumferentially
extending recess 48 and an elongate radially extending track 49 in the bottom
of an
annular circumferentially extending recess 50 identical to recess 48 and
arranged
diametrically opposite recess 48.
The two rings 15, 16 in Fig. 6 and the two rings 9, 10 in Figs 8 and 9 are
arranged
abutting each other with the lateral surfaces thereof provided with the
recesses 48 and
50 facing one another such that recess 48 of ring 15 (ring 9) faces and
overlies recess
50 of ring 16 ( ring 10) and recess 50 of ring 15 (ring 9) faces and overlies
recess 48
of ring 16 (ring 10). Hereby annular channels 51 for receiving the angled end
portions
45 of the arms are formed when the rings of a pair 9/10, 11/12, 13/14 or 15/16
are
arranged abutting each other.
One of the two projecting ends of each guiding pin 46 of each end portion 45
is
inserted in the circumferential track 47 of one ring of a pair of rings while
the other
projecting end is inserted in the radial track 49 of the other ring of said
pair of rings.
The geometry of the tracks 47 and 49 are such that when one ring of a pair of
rings is
rotated relative to the other ring of the pair, then the respective body 38 of
the blade
carried by the pair of rings in question is displaced radially such that the
distance
between the pins 46 of the two arms of the respective blade remains constant
and the
arms are not subjected to any torsional stresses.
In Figs. 8 and 9 the ring pair 9/10 is shown with ring 9 abutting and
overlying ring 10.
In the illustration both rings are shown in full lines for the sake of clarity
and to illustrate
the relative positions of the tracks 47 and 49 of both rings.
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In Fig. 8 ring 10 has been turned 10 degrees clockwise such that the track 47
thereof
shown at left in Fig. 8 is turned 10 degrees clockwise while ring 9 has been
turned 10
degrees counterclockwise so that track 47 thereof shown at right in Fig. 8 is
turned 10
degrees counterclockwise. Consequently track 49 of ring 10 shown at right in
Fig. 8 is
turned 10 degrees clockwise while track 49 of ring 9 shown at left in Fig. 8
is turned 10
degrees counterclockwise. The angles clockwise and counterclockwise are given
relative to an initial position where the body 38 is at the halfway position
between Fig.8
and Fig.9. The maximum periphery of the light beam is shown by the circle 52.
In Fig. 9 ring 10 has been turned 10 degrees counterclockwise such that track
47
thereof shown at left in Fig. 9 is turned 10 degrees counterclockwise while
ring 9 has
been turned 10 degrees clockwise so that track 47 thereof shown at right in
Fig. 9 is
turned 10 degrees clockwise. Consequently track 49 of ring 10 shown at right
in Fig. 9
is turned 10 degrees counterclockwise while track 49 of ring 9 shown at left
in Fig. 9 is
turned 10 degrees clockwise.
All intermediate positions between the two end positions shown in Figs. 8 and
9 are
achieved by rotating the rings 9 and 10 relative to one another the
corresponding
amount of degrees between zero and twenty.
A multitude of different beam periphery shapes may be achieved by displacing
the
blades 30-33 radially by rotating the two rings of the corresponding ring pair
relative to
one another and by displacing the blades circumferentially by rotating the two
rings of
a ring pair together.
In Fig. 7 one of infinitely many combinations of radial and circumferential
positions of
the four blades 30-33 is shown whereby a beam 44 with the shown eight sided
polygonal periphery shape is achieved.
So as to achieve that the distance between the two pins 46 at the ends of the
two
arms of each of the blades 30-33 is the same for all radial displacements of
the body
38 thereof and that no torsion of the arms takes place such that the body 38
is not
subjected to any distorting forces, the shapes of the tracks 47 and 49 are
configured
accordingly as described in the following with reference to Fig. 10 which
illustrates the
construction and calculation of the said shapes of the tracks 47 and 49.
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In Fig. 10 three pairs of mutually corresponding points on the curves 47 and
49 are
constructed, the angles being exagerated for the sake of clarity.
The construction of the curves is carried out according to the following:
Al is constant and equal to half the distance between the two pins 48 of a
blade.
C2 = A1
Anglel = Angle2
Angle1 + Angle2 = Angle3
Both triangles are right-angled triangles
Angle1 is the angle at which ring1 is set and Angle2 is the angle at which
ring2 is set
By rotating ring 1 relative to ring2 Angle3 is obtained. A cebtre line is
constructed from
the centre of the rings and horizontally to the left such that Angle1 =
Angle2.
Anglel and Angle2 are used to construct two triangles.
A line is drawn along the centre line, the line having a length equal to half
the length
between the two pins 46 of a blade.
This line forms the hypotenuse C2 as well as the triangle side Al so that the
other
triangle side B1 can be constructed by drawing a line from the right angle
downwards
and Cl away from the centre until the two lines intersect at a point. This
point is on the
curve to be constucted for configuring track 47.
Equation 1.1: B1 = SIN(Angle1) x A1
Equation 1.2: C1 = A1/COS(Angle1)
Cl is now a radius which together with Angle3 may used to construct the track
by
means of the equations 1.3
Xtrack47 = COS(Angle3)xCl
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Ytrack47 = SIN(Angle 3)xC1
Or the equation 1.2 may be inserted in the equation 1.3
Xtrack47 = COS(Angle3) x (A1/COS(Angle1))
Ytrack47 = SIN(Angle3) x (A1/COS(Angle1))
The X and Y axes being as indicated in Fig. 10 for each point constructed.
The track 49 in one ring extends in the radial direction to take up the radial
displacement of the corresponding end of the pin 46 arising from the geometry
of the
track 47 in the other ring.
As it is the intersection point or triangle apex B1/C1 that alters its
position relative to
the centre of the rings, the shape of the track 47 is given by:
X track49 = A1/COS(Angle1)
Ytrack49 = 0
such that the fixed distance is maintained between the ends of the pins 46 in
corresponding points of tracks 47 and 49.
Those skilled in the art will readily appreciate that It is possible to
achieve
displacement of beam shaping blades radially and circumferentially by means of
rotating rings in many other ways.
Referring now to Fig. 11, an alternative way of arranging the beam influencing
blades
is shown schematically. Two adjustment rings 56, 57 similar to the adjustment
rings
9,10 of Figs. 8 and 9 are arranged abutting each other with a beam shaping
blade 60
arranged therebetween and attached to the rings by means of two guiding pins
61 and
62. Pin 61 is received in a recess in the lateral surface of ring 57 facing
ring 56, the
recess having a shape that only allows rotation of the pin 61 therein. Pin 62
is received
in a linear track 63 recessed into the lateral surface of ring 56 facing ring
57. The pin
62 may slide in the track 63.
The situation wherein the blade 60 maximally obstructs the beam of light 52 is
shown
in full lines while the situation wherein the blade 60 does not obstruct the
beam 52 is
shown in dotted lines. The fully obstructing position of blade 60 is amended
to the non-
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obstructing position thereof by rotating the ring 56 and 57 relative to one
another for
instance as shown by rotating ring 56 counterclockwise and maintaining ring 57
in the
same position. Hereby the pin 62 will be forced to slide in the track 63 while
the pin 61
merely rotates such that the blade rotates around the pin 61. In the shown
example a
5 rotation of ring 56 counterclockwise 12 degrees will result in a rotation of
22 degrees of
the blade 60.
This arrangement of the beam shaping blades requires relatively stiff blades
and/or
relatively large axial spacing between the individual blades so as to avoid
that the
blades interfere with or engage one another when being rotated.
10 Referring now to Figs. 2, 3, 12 and 13, the mechanism for displacing the
focusing lens
22 and the zoom lens 23 along the longitudinal axis 19 is shown in partly
exploded
form. Holder 64 for the zoom lens 23 and holder 65 for the focusing lens 22
are
slidingly arranged in tracks 66 and 67, respectively, in track rails so that
the holders
64 and 65 may be displaced to and fro parallel to the longitudinal axis 19.
15 A bracket 68 is connected to each of the hoiders 64 and 65, only the
bracket 68 for the
holder 65 being visible. The brackets are each connected to a respective
toothed belt
69 and 70 corresponding to holders 65 and 64, respectively the toothed belts
are
mounted on pulleys 71 and 72 rotatably mounted on the track rails 66, 67.
Each of the adjustment rings 17 and 18 (partly cut away for clarity in Fig.
12) are
provided with lateral toothed portions 73 and 74, respectively, for engaging
the teeth of
toothed belts 69 and 70, respectively, so that rotation of ring 17 to and fro
will cause
displacement of toothed belt 69 to and fro, and rotation to and fro of ring 18
will cause
displacement to and fro of toothed belt 70. Hereby, the lens holders 64 and 65
may be
displaced to and fro along tracks 66 and 67 by rotation to and fro of rings 18
and 17,
respectively.
Hereby, a simple, precise and relatively silent displacement mechanism is
achieved for
adjusting the position of the lenses along the longitudinal axis.
When the lighting fixture 1 is oriented with the axis 19 thereof steeply
inclined, i.e.
pointing upwards or downwards steeply, the weight of the lenses, particularly
the zoom
lens 23 will tend to force the lens up or down from the desired and adjusted
position,
especially if vibration of the fixture takes place. This tendency can be
curtailed or
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eliminated by introducing an inertia or braking in the displacement mechanism.
However, if the inertia is present constantly, for instance a constant brake
force
applied to the toothed beits, then displacement of the lens will require
additional
tangential force applied to the rims of the rings 17 and 18. Naturally, this
is
undesirable both for manual operation requiring greater exertion of force by
the
operators fingers and for motorised operation requiriing a more powerful motor
with
attendant cost and noise increase consequences.
The displacement mechanism according to the invention is provided with a
braking
function that only is effective when displacement of the lens is not taking
place, i.e. the
braking function is only in force when the rings 17 or 18 are not being
rotated. The
principles of the selective braking mechanism according to the invention and
described
in the following are of course also applicable in other applications where a
displacement of an object with subsequent braking of the object in the
displaced
position is desirable.
The selective braking mechanism (Figs. 12-13) according to the invention
comprises
the pulley 71, a locking wheel 90, a friction washer 91, a friction spring 92,
a locking
washer 93 and a locking sled 94.
The spring 92 presses the locking wheel 90 and the friction washer 91 against
the
pulley 71 so as to create a suitable friction between the locking wheel 90 and
the
pulley 71.
The locking sled 94 is arranged between the two parallel lengths of the
toothed belt
and for displacement to and fro in the plane of said toothed belt 70 at
perpendicularly
to said two parallel lengths. The locking sled is provided with locking teeth
94a and
94b for locking engagement with teeth at the rim of locking wheel 90 in a
ratchet type
action. If the locking sled 94 is in a central position, i.e. not displaced
towards any of
the two parallel lengths of the belt 70, then the locking teeth 94a and 94b
will not
engage the teeth of the locking wheel 90 so no friction brake is applied to
the belt 70.
The dimension of the locking sled 94 perpendicular to the parallel lengths of
the belt
70 is slightly longer than the distance the commone tangents of the pulleys 71
and 72
such that in the central position of the locking sled 94 sid locking sled will
press
against the parallel lengths of belt 70.
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If tension is applied to one of the parallel lengths of the toothed belt 70
because of the
weight of the lens, said length will be tightened and the parallel length will
be loosened
whereby the locking sled will be displaced from the central position to a
lateral position
where the respective one of the locking teeth 94a and 94b will engage the
ratchet
teeth of the locking wheel 90 thereby applying frictional braking forces to
the pulley 71
through the friction washer 91.
However, if tension in one of the parallel lengths of the belt 70 is caused by
rotation of
the ring 18 for axial displacement of the holder 64, then the displacement of
the
locking sled 94 from the central position thereof will not cause engagement of
one of
the locking teeth 94a or 94b with the ratchet teeth of the locking wheel 90 as
the
ratchet effect will cause the respective locking tooth to "ratchet" over the
ratchet teeth.
Hereby, a selective braking mechanism is achieved whereby the brake effect is
operative, when the weight of the lens tries to rotate the respective
adjustment rings,
but the brake effect is inoperative when rotation of the respective ring is
carried out to
displace the lens axially.
It will be apparent to those skilled in the art that the principles of the
above selective
braking mechanism may be applied in all applications where a braking effect is
required in one direction of force application and is not required in the
opposite
direction of force application.
The arrangement of the gobo or pattern 29 in the ring 8 and the iris 28 in the
ring 7
need not be described herein as it will be apparent to those skilled in the
art that this
can be done in many ways well known in the art.
For remote control of the adjustment rings it will also be readily apparent to
those
skilled in the art that an electrical motor with a pinion for each ring may be
arranged
such that the teeth of the pinion mesh with the teeth on the rim of the
respective ring.
The motors may for instance be firmly attached to the frame 6 or be spring
biased so
that any irregularities in the mounting of the rings and thereby the teethed
rims may be
taken up. Magnetic markers may be attached to the rings such that a sensing
means
may sense the marker and thereby precisely identify the position of the
respective ring
as a basis for the subsequent rotation thereof to a new setting of the
respective beam
influencing means.
