Optics: image projectors – Lens support – Lens position adjustable
Reexamination Certificate
1999-12-28
2001-01-09
Dowling, William (Department: 2851)
Optics: image projectors
Lens support
Lens position adjustable
C353S098000, C353SDIG003, C353SDIG006, C353S101000
Reexamination Certificate
active
06170954
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates generally to overhead projectors for projecting images above or behind an operator, and more particularly to an overhead projector of the under mirror type in which a reflecting mirror is disposed on a lower portion of a projection head assembly including a projection lens and the mirror.
2. Description of the prior art
Overhead projectors are roughly classified into an over mirror type and an under mirror type. Overhead projectors of the over mirror type comprise a housing having a stage formed on the top thereof and a projection head assembly including a projection lens and a reflecting mirror. The projection head is supported on a column or mast so as to be disposed over the stage. Light from a light source is caused to pass through a transparency bearing an image to be projected and placed on the stage and then the projection lens. The light is then reflected on the mirror so that the image is focused on a screen. A projection angle is readily adjusted by adjustment of an angle of the mirror in the overhead projectors of the over mirror type. However, the mirror protrudes over the projection head assembly and this reduces an easiness to use the overhead projectors.
On the other hand, in overhead projectors of the under mirror type, light from a light source is caused to pass through a transparency and then to reflect on a reflecting mirror. The light is subsequently caused to pass through a projection lens to be focused on a screen. The mirror is located at a lower side of a foldable projection head assembly in the overhead projectors of the under mirror type. This enhances the easiness to use the overhead projectors. However, angles of both of the mirror and the projection lens need to be adjusted for the purpose of adjustment of the projection angle. Furthermore, these angles need to be adjusted so that the angle of the projection lens doubles the angle of the mirror. This construction requires an interlocking mechanism which interlocks the projection lens and the mirror for adjustment of the angles of them.
Japanese Utility Model Registration No. 3043179 discloses an overhead projector of the under mirror type provided with such an interlocking mechanism as described above. In the disclosed overhead projector, an angle adjusting knobbed bolt is turned so that the angle of the mirror is adjusted. The angle of the projection lens is adjusted by the interlocking mechanism simultaneously with that of the mirror so as to double the angle of the mirror.
In the disclosed overhead projector, however, the knobbed bolt is mounted on the projection head assembly so as to be turnable and movable back and forth. The bolt is moved to protrude from the projection head assembly when the latter is folded in a case where the overhead projector is not in use. As a result, the projection head assembly cannot compactly be folded. Furthermore, the bolt rattles when the overhead projector is carried with the head assembly folded.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an overhead projector of the under mirror type in which the projection head assembly can compactly be folded.
Another object of the invention is to provide an overhead projector of the under mirror type in which the projection head assembly can be prevented from rattling while the overhead projector is carried with the head folded.
Further another object of the invention is to provide an overhead projector of the under mirror type in which the projection head assembly and the column supporting the head assembly can compactly be folded.
The present invention provides an overhead projector of the under mirror type comprising a housing including a stage formed on a top thereof so that a transparency bearing an image to be projected is placed on the stage and a projection head assembly including a head body further including a reflecting mirror on which light passing through the transparency on the stage reflects and a projection lens focusing the light incident thereon on a screen, the projection head assembly being supported on a column so as to be located over the stage and so as to be movable between a standing position and a stowed position. A head positioning element positions the projection head assembly at the standing position. A head locking element releasably locks the projection head assembly at the stowed position. The projection lens is fixed on a lens frame and the reflecting mirror is fixed on a mirror plate. Both the lens frame and the mirror plate are rotatably mounted on a single shaft further mounted on the head body of the projection head assembly so that angles of the lens and the mirror are increased and decreased. The lens frame is rotated by a self-weight of the lens in such a direction that the angle of the lens is decreased, when the projection head assembly assumes the standing position. A link lever interconnects the lens frame and the mirror plate so that the angles of the projection lens and the mirror are adjusted so that the angle of the lens doubles the angle of the mirror. A mirror locking element releasably locks the mirror at a position where the angle of the mirror is maximum. An angle adjusting knobbed bolt is mounted on the head body so as to be turnable and immovable back and forth. An angle adjusting piece is screwed on the knobbed bolt so as to be unturnable and movable back and forth. The mirror plate has an end departed from the angle adjusting piece when the mirror plate is rotated in such a direction that the angle of the mirror is increased. The end of the mirror plate engages the angle adjusting piece when the mirror frame is rotated in such a direction that the angle of the mirror is decreased.
According to the above-described construction, the angle adjusting piece is moved back and forth along the knobbed bolt when the knobbed bolt is turned. The mirror plate engaging the adjusting piece is rotated about the shaft such that the angle of the mirror is adjusted. The lens frame connected with the mirror plate by the link lever is simultaneously rotated so that the angle of the projection lens is adjusted so as to double the angle of the mirror.
In order that the projection head assembly may be folded, the projection lens is rotated in such a direction that the angle thereof becomes maximum. Then, the mirror plate interconnected with the lens frame by the link lever is also rotated in such a direction that the angle thereof becomes maximum. The end of the mirror plate then departs from the angle adjusting piece. When the projection lens is further rotated to the position where the angle thereof becomes maximum, the mirror is also rotated to the maximum angle position, where the mirror is locked by the locking element. The projection lens interconnected with the mirror by the link lever is also locked. Then, the projection head assembly is rotated to the stowed position and locked at the stowed position by the head locking element.
Since the knobbed bolt mounted on the head body is turnable and unmovable back and forth, the knobbed bolt is disallowed to move with the mirror or the projection lens when the projection head assembly is folded. Thus, the projection head assembly can compactly be folded since the knobbed bolt does not protrude therefrom.
The head locking element preferably includes a locking pin protruding from an arm fixed to the column, a head locking member slidably fitted with the arm and having on an end face thereof an engagement recess, and a spring urging the head locking member along the arm so that an end face of the head locking member abuts against the locking pin, and wherein the locking pin engages the recess such that the projection head assembly is locked at the stowed position and the locking element is slid against a spring force of the spring so that the locking pin disengages from the recess such that the projection head assembly is released from a locked state.
The mirror locking element preferably includes a mirror locking member m
Kai Mutsuo
Sukenari Kazuhiro
Dowling William
Elmo Co., Ltd.
Koda & Androlia
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