Note: Descriptions are shown in the official language in which they were submitted.
CA 02341918 2001-03-19
OVERHEAD PROJECTION SYSTEM
Field Of The Invention
The present invention relates generally to projection systems and in
particular to an overhead projection system and to an overhead projector
support
assembly.
Background Of The Invention
Overhead projection systems are well known in the art and typically
include a ceiling mounted projector that is spaced from and aimed downwardly
at a
generally planar display surface onto which projected images are to be
displayed.
1o Unfortunately, ceiling mounted projectors suffer from a number of
disadvantages.
For example, some types of ceilings such as drop tile ceilings, do not provide
the
necessary support structure for overhead projectors. As a result, structural
reinforcements for ceilings of this nature are necessary before overhead
projectors can
be ceiling mounted. Also, HVAC and/or lighting may be positioned on the
ceilings at
15 the positions where it is necessary to mount the projectors. If so, the
HVAC and/or
lighting must be moved before the projectors can be mounted. Furthermore,
ceiling
mounted projectors typically require specialized power and signal wiring that
must be
installed in the ceilings. In addition, registering ceiling mounted projectors
with
display screens requires specialized skill and calculations on the part of
installers and
2o typically leads to the use of expensive projectors with zoom and lens shift
capabilities.
These above-described problems result in expensive and onerous installations.
Mounting a projector to a wall surface has also been considered. For
example, U.S. Patent No. 5,490,655 to Bates discloses a video/data projector
and
monitor ceiling/wall mount. The wall mount includes a wall support assembly
fixedly
25 secured to a wall surface. A pair of struts extends horizontally from the
wall support
assembly. A projector/monitor adapter is supported by the ends of the struts.
The
wall support assembly includes a strut adapter that rests between a pair of
adapter
plates extending from a wall plate. A fastener secures the strut adapter to
the adapter
plates in a manner to permit rotation of the adapter plate and hence, the
struts about a
30 vertical axis.
Although Bates discloses an assembly for supporting a projerxor that-is
to be secured to a wall surface, the Bates wall mount suffers disadvantages.
When a
load is placed on the wall mount, the entire load is taken up by the wall
mount and the
wall surface due to the fact that the wall mount is static. If the load is
significant, the
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load may cause damage to the wall mount and/or the wall surface. In addition,
if it is
necessary to service the wall mount and/or the projector supported thereon, a
ladder or
other similar device must be used to gain access to the wall mount and/or
projector.
As will be appreciated, improved overhead projection systems are desired.
It is therefore an object of the present invention to provide a novel
overhead projection system and a novel overhead projector support assembly.
Summary Of The Invention
According to one aspect of the present invention there is provided an
1 o overhead proj ection system comprising:
an overhead projector support assembly extending outwardly from a
generally vertical support surface in a generally horizontal disposition;
a display screen having a display surface mounted on said support
surface beneath said projector support assembly; and
15 a projector mounted on said projector support assembly and aimed to
project images onto the display surface of said display screen.
Preferably, the projector support assembly is pivotably mounted on the
support surface and is moveable from the generally horizontal disposition
downwardly when a load is placed on the projector support assembly. A governor
2o controls pivotal movement of the projector support assembly in a manner so
that the
boom pivots downwardly under a load generally at an unconstrained rate to
avoid
damage to the overhead projection system and/or support surface.
In a preferred embodiment, the governor is a damper and spring
arrangement that automatically returns the projector support assembly to the
generally
25 horizontal disposition when the load is removed at a controlled generally
constant
rate. A releasable locking mechanism carried by the damper and spring
arrangement
is actuable to retain the projector support assembly in a downwardly extending
condition.
In the preferred embodiment, the projector support assembly includes a
3o single boom. The boom has one end pivotally coupled to the support surface.
The
projector is suspended from the opposite end of the boom with the damper and
spring
arrangement being disposed on the boom intermediate its ends. The damper and
spring arrangement is constituted by a gas spring having one end fixed to the
boom
and an opposite end fixed to an element moveable along the boom. The moveable
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element moves along the boom towards the fixed end during downward pivoting of
the boom thereby to compress the gas spring.
Preferably, the display screen is pivotally mounted on the support
surface to allow the bottom of the display surface to be tilted towards the
projector.
The display screen may be a touch panel that generates control signals
representing
contacts with the touch panel. In this case, the overhead projection system
further
includes a computer that executes an applications program and provides image
output
to the projector. The touch panel, computer and projector form a closed loop
to
define an interactive display system whereby control signals generated by the
touch
1 o panel are used by the computer to update the applications program and the
image
output provided to the projector. A console is disposed beneath the display
screen
and houses the computer.
In another embodiment, the support surface is an upright support
member that is mounted on a wheeled cart. This allows the overhead projection
system to be wheeled to the desired location making the overhead projection
system
fully portable.
According to another aspect of the present invention there is provided
an overhead projection system comprising:
an overhead projector support assembly extending outwardly from a
2o generally vertical support surface in a generally horizontal disposition;
a display screen having a display surface mounted on said support
surface beneath said projector support assembly;
a proj ector mounted on said proj ector support assembly; and
at least one reflective surface positioned to reflect images projected by
said projector onto said display surface.
In one form, the overhead projection system is used in a rear projection
environment. In this case, the display screen is mounted on the support
surface and
positioned so that the display surface covers an opening therein. The display
surface
is translucent so images projected onto the back of the display surface are
visible
3o when looking at the front of the display surface. In one embodiment, the
projector is
aimed away from the support surface. A mirror is mounted on the projector
support
assembly adjacent a distal end thereof and is positioned to reflect projected
images
backward onto the display surface of the display screen. In another
embodiment, the
projector is aimed towards the support surface. A pair of mirrors is mounted
on the
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projector support assembly. A first mirror is positioned in front of the
projector and a
second mirror is positioned behind the projector. The first mirror is
positioned to
reflect projected images away from the support surface onto the second mirror.
The
second mirror is positioned to reflect projected images backward onto the
display
surface of the display screen.
According to yet another aspect of the present invention there is
provided an overhead projector support assembly comprising:
at least one boom adapted to extend outwardly from a generally
vertical support surface in a generally horizontal disposition and to support
a projector
to at a location spaced from said support surface;
at least one coupling element adapted to couple pivotally one end of
said at least one boom to said support surface to enable said at least one
boom to be
pivoted downwardly from said generally horizontal disposition under a load;
and
a governor to control pivotal movement of said boom.
15 According to still yet another aspect of the present invention there is
provided a portable overhead projection system comprising:
a portable upright support member;
an overhead projector support assembly extending outwardly from said
support member in a generally horizontal disposition;
2o a display screen having a display surface mounted on said support
member beneath said projector support assembly; and
a projector mounted on said projector support assembly and aimed to
project images onto the display surface of said display screen, wherein said
projector
support assembly is pivotable from said horizontal disposition downwardly when
a
25 load is placed thereon.
The present invention provides advantages in that since the projector
support assembly, which supports the projector, and the display screen are
mounted
on the same support surface, the projector and the display screen can be
registered
consistently and quickly. Also, since the boom pivots downwardly at a
generally
3o unconstrained rate whenever a load is placed on the boom and since the
pivotal
movement is controlled by the governor, the potential for damage to the
overhead
projection system and/or the support surface is significantly reduced.
The present invention also provides advantages in that since the
projector support assembly can be pivoted downwardly and locked in position,
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maintenance and servicing of the projector and related cabling is facilitated
obviating
the need for a ladder or other similar device.
Brief Description Of The Drawings
Embodiments of the present invention will now be described more
fully with reference to the accompanying drawings in which:
Figure 1 is an isometric view of an overhead projection system in
accordance with the present invention;
Figure 2 is front elevational view of the overhead projection system of
Figure 1;
Figure 3 is a top plan view of the overhead projection system of Figure
1;
Figure 4a is an isometric view of a governor forming part of the
overhead projection system of Figure 1;
Figure 4b is a cross-sectional view of Figure 4a;
Figure 5 is a side elevationai view of a projector mounting assembly
forming part of the overhead projection system of Figure 1;
Figure 6 is a top plan view of the projector mounting assembly of
Figure 5;
2o Figure 7 is a side elevational view of the overhead projection system of
Figure 1 showing the boom in a generally horizontal disposition and in a
downwardly
extending condition;
Figure 8 is an enlarged portion of Figure 7;
Figure 9 is a side elevational view of another embodiment of an
overhead projection system in accordance with the present invention;
Figure 10 is a side elevational view of yet another embodiment of an
overhead projection system in accordance with the present invention; and
Figure 11 is a side elevational view of still yet another embodiment of
an overhead projection system in accordance with the present invention.
Detailed Description Of The Preferred Embodiments
Turning now to Figures 1 to 3, an overhead projection system in
accordance with the present invention is shown and is generally identified by
reference numeral 20. As can be seen, overhead projection system 20 includes
an
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overhead projector support assembly 22 that extends outwardly from a generally
vertical support surface 24, such as a wall, in a generally horizontal
disposition. A
touch-sensitive display screen 26, such as that sold under the name SmartBoard
by
Smart Technologies Inc. of Calgary, Alberta, Canada, is also mounted on the
wall 24
beneath the projector support assembly 22. A projector 28 is mounted on the
projector support assembly 22 adjacent its distal end and is aimed to project
images
directly onto the display surface 26a of the touch sensitive display screen
26.
A console 30 is positioned beneath the touch sensitive display screen
26 and includes a pair of doors 32 and 34. A personal computer 36 executing
one or
1o more applications programs is supported on the inside of the door 32 while
other
peripherals such as for example, audiovisual equipment 38 is supported on the
inside
of the door 34. The audiovisual equipment 38 is connected indirectly to a pair
of
speakers 40 that is mounted on the console 30 above the doors 32 and 34 by way
of
the personal computer 36. With the doors 32 and 34 of the console 30 closed,
the
15 personal computer 36 and the audiovisual equipment 38 are conveniently
housed.
The personal computer 36, touch-sensitive display screen 26 and
projector 28 form a closed loop to define an interactive display system of the
type
disclosed in U.S. Patent Nos. 5,448,263 and 6,141,000 to Martin, assigned to
the
assignee of the present invention, the contents of which are incorporated
herein by
2o reference. Thus, the touch sensitive display screen 26 outputs control
signals in
response to contacts made on the display surface 26a of the touch sensitive
display
screen 26. The control signals are conveyed to the personal computer 36, which
uses
the control signals to update the applications program being executed and to
update
the image output of the projector 28.
25 Turning now to Figures 1, 3, 4a and 4b, the projector support assembly
22 is better illustrated. As can be seen, the projector support assembly 22
includes a
boom 50 configured as a two-part telescoping arrangement. Specifically, the
boom SO
includes a main fixed length extrusion 52 and an extension 54 extending
axially from
the distal end of the main extrusion. The main extrusion 52 has one end
pivotally
3o mounted on a bracket 56 that is secured to the wall 24 by suitable
fasteners (not
shown). Guide channels 58 are formed in opposite sides of the main extrusion
52. A
channel 60 is also provided in the undersurface of the main extrusion 52 to
accommodate cabling 62 that extends between the personal computer 38 and the
CA 02341918 2001-03-19
projector 28. A cap 64 runs along the bottom of the main extrusion 52 to hold
the
cabling 62 within the channel 60
The extension 54 is slidably received by an internal channel formed in
the main extrusion 52 and has a plurality of threaded calibration holes (not
shown)
provided therein. A locking fastener 68 is rotatable to engage a selected
calibration
hole. In this manner, the length by which the extension 54 extends axially
from the
main extrusion 52 can be adjusted. A channel 69 is also provided in the
undersurface
of the extension 54 to accommodate cabling 62. A cap 70 runs along the bottom
of
the extension to hold the cabling within the channel.
1o A depending arm 72 is coupled to the distal end of the extension 54 by
a lockable joint 74. The arm 72 supports a projector mounting assembly 90 as
best
seen in Figures 5 and 6. The projector mounting assembly 90 includes upper and
lower generally rectangular plates 92 and 94 that are spaced apart by a
flexible
bushing 96 formed of rubber. A fastener 98 passes through the bushing 96 to
secure
the plates 92 and 94 together. The lower plate 94 has a plurality of keyhole
slots 100
provided therein. The keyhole slots 100 accommodate pins 102 extending
upwardly
from the top of the projector 28. The larger diameter portions 100a of the
keyhole
slots 100 are threaded to accommodate tamperproof fasteners (not shown) to
inhibit
the projector 28 from being removed from the projector mounting assembly 90.
2o The projector mounting assembly 90 also includes a pair of adjustment
mechanisms 104 to allow the lower plate 94 to be tilted with respect to the
upper plate
92 thereby to orient the projector 28 so that the projector and touch
sensitive display
screen 26 are registered. Each adjustment mechanism 104 includes an externally
threaded rod 108 that engages a threaded hole in the upper plate 92. A knob
110 is
provided on the end of the rod 108 that is above the upper plate 92. The other
end of
the rod 108 is coupled to the lower plate 94. Thus, when the knob 100 is
rotated, the
threaded rod 108 advances either towards or away from the lower plate 94
depending
on the direction of rotation. This of course pulls or pushes on the lower
plate
resulting in the lower plate 94 tilting with respect to the upper plate 92
about the
3o flexible bushing 96.
A boom movement governor 120 is disposed on the main extrusion 52
intermediate the bracket 56 and the projector 28 and controls pivotal movement
of the
boom 50. In this embodiment, the governor 120 is a damper and spring
arrangement
including a block 122 and a sleeve 124 on the main extrusion 52 that are
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_g_
interconnected by a gas spring 126. Block 122 is disposed on the distal end of
the
main extrusion 52 while sleeve 124 is disposed on the main extrusion 52
between the
block 122 and the wall 24.
Block 122 is fixed to the main extrusion 52 to inhibit its movement and
accommodates the locking fastener 68. One end of the gas spring 126 is secured
to
the block 122. Sleeve 124 is slidable along the main extrusion 52 and has
formations
thereon that are received by the guide channels 58 thereby to guide movement
of the
sleeve 124 along the main extrusion 52. A releasable locking mechanism in the
form
of a brake 146 is provided on the sleeve 124. The brake 146 is actuable
between a
locked condition where the brake contacts the main extrusion 52 to inhibit
sliding
movement of the sleeve 124 and an unlocked condition where the sleeve 124 is
slidable along the main extrusion 52. The brake 146 is typically maintained in
the
unlocked condition to permit the sleeve 124 to slide along the main extrusion
52. The
other end of the gas spring 126 is secured to the sleeve 124. A pair of struts
152
extends between the sleeve 124 and the wall 24. The struts 152 are pivotally
coupled
to opposite sides of the sleeve 124 and are pivotally coupled to a bracket 156
secured
to the wall 24 below the bracket 56.
The display screen 26 is also coupled to the bracket 156. The
connection between the bracket 156 and display screen 26 permits pivotal
movement
of the display screen 26. Specifically, the bottom of display screen 26 can be
pulled
away from the wall 24 to introduce a tilt to the display surface 26a thereby
allowing
keystone correction to be effected. The slight tilt of the display screen 26
towards the
projector 28 also facilitates writing on the display surface 26a.
During operation, the personal computer 36, which executes an
applications program, provides image output that is conveyed to the projector
28 via
the cabling 62. The projector 28 in turn projects images that are displayed on
the
display surface of the touch sensitive display screen 26. When a user contacts
the
display surface 26a, the display screen 26 conveys control signals to the
personal
computer 36. The personal computer 36 uses the control signals to update the
3o applications program and the image output conveyed to the projector 28.
When a load is placed on the boom S0, the boom 50 pivots
downwardly about the bracket 56 with the pivotal movement being controlled by
the
governor 120. In particular, as the boom 50 pivots downwardly, the struts 152
also
pivot causing the sleeve 124 to slide along the main extrusion 52 towards the
fixed
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block 122. This of course compresses the gas spring 126 that interconnects the
fixed
block 122 and the sleeve 124 as shown in Figures 7 and 8. Compression of the
gas
spring 126 controls the pivotal movement of the boom 50 in a manner so that
the
boom 50 pivots downwardly at a generally unconstraint rate. This quick
response
movement of the boom 50 avoids damage to the overhead projection system 10
and/or
to the wall 24. Once the load is released from the boom 50, the gas spring 126
expands to return the boom 50 automatically to its generally horizontal
disposition at
a controlled generally constant rate that avoids damaging the overhead
projection
system as well as injury to individuals.
1o If the boom 50 is pivoted downwardly to service the overhead
projection system 10, once the boom 50 has assumed the desired downwardly
extending condition, the boom 50 can be retained in position by actuating the
brake
146 on the sleeve 124. When actuated, the brake 146 engages the main extrusion
52
to inhibit sliding of the sleeve 124 along the main extrusion. This in turn
inhibits
pivoting of the struts 152 and thereby retains the boom 50 in position. With
the boom
50 in this orientation, the projector 28 and the cabling 62 are easily
accessible thereby
facilitating maintenance and serviceability of overhead projection system 10.
Once
servicing has been completed, the brake 146 simply needs to be released to
permit the
sleeve 124 to slide along the main extrusion 52. This allows the gas spring
126 to
2o return the boom 50 to its generally horizontal disposition.
Although the governor 120 as shown and described is a damper and
spring arrangement, those of skill in the art will appreciate that other
mechanisms to
control pivotal movement of the projector support assembly to avoid damage to
the
projector support assembly and/or support surface can be used. For example, a
clutch
may be used to couple pivotally the boom 50 and the bracket 56. The clutch
limits the
force on the bracket 56 when a load is applied to the boom and enables
downward
motion of the boom 50 without allowing the boom 50 to free fall under the
load. In
this case a user is required to pivot the projector support assembly back to
the
generally horizontal disposition after the projector support assembly has been
pivoted
downwardly.
Turning now to Figure 9, another embodiment of an overhead
projection system is shown and is generally identified by reference numeral
220. In
this embodiment, like reference numerals will be used to indicate like
components
with a "200" added for clarity. As can be seen, overhead projection system 220
is
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similar to that of the previous embodiment. However, in this embodiment, a
reflective surface in the form of a mirror 290 is suspended from the distal
end of the
boom 250, with the mirror 290 facing the back of a rear projection display
screen 226.
The projector 228 is mounted on the boom 250 intermediate the length of the
boom
250 and is aimed at the mirror 290.
The display screen 226 is mounted on the wall 224 and is positioned so
that its display surface covers an opening 294 in the wall. The display
surface is
generally translucent.
During operation of the overhead projection system 220, images
to projected by the projector 228 are directed toward the mirror 290. The
mirror 290 in
turn reflects the projected images backward onto the back of the display
surface of the
display screen 226. Since the display surface is translucent, images projected
onto the
back of the display surface are visible to viewers looking at the front of the
display
surface. By placing the projector 228 intermediate the length of the boom 250
and
15 using a mirror 290 to reflect projected images backward onto the display
screen 226,
the length of the boom 250 can be reduced.
Turning now to Figure 10, yet another embodiment of an overhead
projection system is shown and is generally identified by reference numeral
320. In
this embodiment, like reference numerals will be used to indicate like
components
20 with a "300" added for clarity. As can be seen, overhead projection system
320 is
also similar to that of the second embodiment but includes a pair of mirrors
390 and
392 mounted on the boom 350. Mirror 390 is suspended from the distal end of
the
boom 350 and faces the display screen 326. Mirror 392 is mounted on the boom
350
intermediate its length and faces the mirror 390.
25 During operation of the overhead projection system 320, images
projected by the projector 228 are directed toward the mirror 392. The mirror
392
reflects the projected images backward onto the mirror 390. The mirror 390 in
turn
reflects the projected images backward onto the back of the display surface of
the
display screen 326. Using two mirrors allows the length of the boom 350 to be
even
30 further reduced.
Turning now to Figure 11, still yet another embodiment of an overhead
projection system is shown and is generally identified by reference numeral
420. In
this embodiment, like reference numerals will be used to indicate like
components
with a "400" added for clarity. The overhead projection system 420 is similar
to that
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of the first embodiment but is a self contained portable unit. As can be seen,
the
boom 450 is pivotally coupled to an upright support member 496 by way of a
mounting bracket 456 mounted near the top of the support member 496. Support
member 496 is mounted on a wheeled cart 498 allowing the overhead projection
system 420 to be wheeled to the desired location.
In use with the overhead projection system 420 located at the desired
location, the boom 450 is in the generally horizontal disposition so that
images
projected by the projector 428 are displayed on the display screen 426. When
not in
use or during transportation, the boom 450 is pivoted downwardly to a position
where
to the boom is generally parallel with the support member 496. In this
position, the
boom can be retained in position either by engaging the brake on the sleeve
454 or by
using a retaining mechanism 500 that extends outwardly from the support member
496.
As will be appreciated, the overhead projection systems described
15 above can be easily installed by a junior audiovisual technician in a short
period of
time while ensuring registration of the projector and the display surface of
the display
screen. Also, since the display surface is able to tilt thereby to effect
keystone
correction, an inexpensive projector that does not include lens shifting
capabilities can
be used. The tilt of the display screen also facilitates writing on the
display surface.
2o Although the display screen is described as being a SmartBoard touch
sensitive display screen, those of skill in the art will appreciate that other
types of
touch panels may be used. Also, if a closed loop interactive display system is
not
required, any planar surface to display images projected by the projector may
be used.
Although preferred embodiments of the present invention have been
25 described, those of skill in the art will appreciate that variations and
modifications
may be made without departing from the spirit and scope thereof as defined by
the
appended claims.
