Optics: image projectors – Structurally related projector and screen
Reexamination Certificate
2000-06-20
2002-04-30
Adams, Russell (Department: 2851)
Optics: image projectors
Structurally related projector and screen
C353S037000, C353S070000, C353S071000, C353S073000, C353S077000, C353S094000, C353S099000, C353S119000, C353S122000, C353S064000, C348S744000, C348S789000, C348S794000, C348S836000
Reexamination Certificate
active
06379012
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to video projection systems, and, in particular, to a system used to mount a video projector overhead.
BACKGROUND OF THE INVENTION
Video projectors of the type that cast a viewable image onto the front surface of a screen are utilized in a wide variety of venues, such as conference rooms and classrooms. The mounting or installation of such video projectors has taken many forms in the past. In some situations, it has been found highly desirable for the video projector to be stored in a room so as to be as inconspicuous as possible to avoid detracting from the aesthetics of the room. As a result, several video projector mounting systems have been developed to store the video projector overhead and above the ceiling of the room in which it is utilized.
One above ceiling system disclosed previously by Draper, Inc., of Spiceland, Ind., included a housing designed to be suspended from a support structure above a ceiling of a room. A video projector, which was supported on the floor of the housing, cast an image on a first mirror fixedly mounted within the housing, which fixed mirror reflected the cast image through openings in the housing floor and ceiling onto a second mirror that was installed on the upwardly facing surface of a trap door which opened doom into the room at an angle when the projector was to be used. The image cast upon the second mirror when the trap door was opened then reflected back onto a screen in the room for viewing. When the projector was not being used, the trap door was closed so as to cover the opening in the ceiling and to be flush with the ceiling.
While highly desirable in that the video projector was stored out of site, and further that the video projection system, and specifically only the trap door with a mirror, did not extend into the room significantly even during its use, such system was not without its shortcomings. For one thing, the system was not compatible with many types of projectors due to the operating characteristics, such as the light path, of those projectors. For example, when certain projectors were properly situated on the housing so as to cast an image directly on the first mirror, all of the image reflected by the first mirror did not fall on the trap door mirror, and consequently what was reflected onto the screen to be visible was incomplete. Moreover, even when used with projectors for which all of the image reflected by the first mirror did fall on the trap door mirror, the system sometimes resulted in visible images being cast on a location which was unacceptable or undesirable, such as at a height on the projection screen which was higher or lower than desired. And, since moving the projector relative to the first mirror was not a suitable adjustment technique for some projectors, which for optimal operation need to be spaced a particular distance from the first mirror, consistent adjustment of the image location was not readily possible.
A second shortcoming pertained to the imprecise positioning of the pivotable trap door on which the second mirror was installed. Failure to properly orient or angle the second mirror relative to the first mirror results in the image cast on the in-room screen being improperly located along the height of that screen. In an attempt to address this issue, two electrical limit switches were installed in the system. The limit switches were circuited to a reversible motor that rotated a shaft. Linkages attached to the shaft were connected to the trap door to open and close that door when the shaft was rotated in opposite directions. First and second switch actuating arms were connected to the shaft at different points along the shaft length. One of the actuating arms was arranged to rotate and trigger one of the limit switches when the trap door was being opened, and the other actuating arm was arranged to rotate and trigger the other limit switch when the trap door was being closed. While the limit switches when triggered functioned to shut off power to the door-moving motor, the orientation at which the trap door actually stopped depended on how far the shaft rotated under its own inertia after the motor power was removed and was not consistent. Consequently, the trap door was not always tightly shut after being closed. More problematic was the fact that when opened, the trap door and therefore the second mirror were not always angled properly relative to the ceiling for use, resulting in the quality of the viewing experience being lessened due to the projected image not being properly located on the screen.
In another overhead projector mounting system, a shortcoming relates to the limited accessibility to the housed components when installed. While a housing is useful to provide a protective enclosure for the system components, such as the projector and the control hardware, and to possibly serve as a plenum for conveying fan-circulated air, the housing hinders access. For example, since the housing is installed in the space above the room ceiling where frequently little clearance space is present, removing the top of the housing to access the housing interior to service the system components is inconvenient.
Thus, it would be desirable to overcome these and other shortcomings of the prior art.
SUMMARY OF THE INVENTION
The present invention provides a mounting system for an overhead projector which allows for adjustment in the height at which an image is projected on a viewable surface within a room. The system is equipped with a mirror above the ceiling that reflects an image received from the projector onto a mirror on a trap door that extends down into the room. The above ceiling mirror, and preferably the projector as well, is mounted on a carriage which is movable within the system housing and relative to the trap door mirror to adjust where an image is reflected onto the trap door mirror, which adjustment alters where the image reflected by the trap door mirror falls upon a viewing surface. To aid in proper positioning of the mirrored trap door when that door is moved between opened and closed positions, the system preferably includes a door stop control mechanism having both a limit switch, which cuts off power to a door moving motor, and a stop which provides a physical block to further door motion. The system also preferably includes a housing with a sliding cover to facilitate access to the projector and other components within the housing.
In one form thereof, the present invention provides an overhead projector mount system for a room including a support mountable at or above a ceiling of the room, at least one carriage above the ceiling and movable relative to the support, a first mirror mounted to a first carriage of the at least one carriage to be movable with that first carriage, and a second mirror. The first mirror is aligned to receive images projected by a projector mounted to either the support or the at least one carriage and to reflect the images downward through an opening in the ceiling. The second mirror extends below the ceiling of the room to receive images reflected by the first mirror and reflect the images to a viewing surface in the room. Movement of the first carriage between first and second positions adjusts a location on the second mirror at which images are received from the first mirror.
In another form thereof, the present invention provides an overhead projector mount system for a room including a support for a projector mountable at or above a ceiling of the room, a mirror movable between a first orientation and a second orientation, and a drive assembly including a motor. The mirror when in the second orientation extends below the ceiling of the room to receive images generated by the projector which pass through an opening in the ceiling and reflect the images to a viewing surface in the room. The drive assembly is operable to move the mirror between the first and second orientations. The system includes a limit switch, which is circuited with the motor and actuatable by the drive assembly to
Enochs Steven E.
Wilson Robert D.
Bose McKinney & Evans LLP
Cruz Magda
Draper, Inc.
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