Optical: systems and elements – Projection screen – Roll up screen
Reexamination Certificate
1999-08-20
2001-10-02
Adams, Russell (Department: 2851)
Optical: systems and elements
Projection screen
Roll up screen
C359S443000
Reexamination Certificate
active
06297905
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a screen for displaying, on an enlarged scale, an image projected by a projector or a projection TV set and in particular but not exclusively to a portable screen assembly that is easy to carry and can be installed at an optional location such as, for example, on a floor, a table or the like.
2. Description of the Prior Art
An image projected by a projector or, in some cases, a projection TV set is generally displayed, on an enlarged scale, on a reflection type screen or on a transmission type screen.
Of such screens, some are generally accommodated in a housing mounted on a ceiling or a side wall, and are electrically or manually extended as the occasion demands. Hanging screens or screens with a tripod are used by hanging or locating them at a desired place.
Portable screen assemblies are today available in which a screen is wound around a roll housed in a housing. When such screen assemblies are in use, the housing is initially installed at a desired place, and the screen is subsequently extended by, for example, an extension means somewhat similar to a pantograph by the action of the biasing force of a spring mounted therein.
Recently, the number of meetings or conferences has increased in companies or offices and there is an increasing demand for a portable screen assembly having a simple structure that is easy to carry with a projector and can be installed on a floor, a desk or a table in a conference room to display an image projected by the projector.
Further, there is a problem with the conventional pantograph that the pantograph is hard to get balanced laterally (i.e., in right and left symmetry) when it is lifted, and this tends to cause the top bar to tilt. As a result, the screen is wound around the spring-biased roll in a bamboo-like fashion, thus tending to cause the trouble of damaging the screen.
Another problem is that where arms of the pantograph and the spring-biased roll are mounted in an axially misaligned condition, the spring-biased roll and the top bar are not in axially parallel alignment when the screen is stretched and this causes the screen to distort. However, high precision is required to eliminate the possibility of such a problem of distortion when mounting the constituent parts to the pantograph and the pantograph to the lower casing, which results in a high cost of fabrication.
SUMMARY OF THE INVENTION
The present invention was made in view of such requirements and problems and is intended to provide a portable screen assembly which can be readily transported together with a projector and is easy to handle and which is simple in construction and less expensive.
According to an aspect of the present invention, there is provided a portable screen assembly, which includes an upper and a lower casing, a spring-biased roll rotatably mounted on the lower casing, a screen having first and second ends that are opposite to each other and wound around the spring-biased roll at a rest position, a top bar secured to the first end of the screen, a pantograph type expansion means rotatably mounted at one end thereof to the top bar and at the other end thereof to the lower casing for biasing the top bar upwards, and a height retaining means engaged with a portion of the expansion means so as to maintain the screen at a desired height.
The height retaining means preferably includes one of a gas spring and a coil spring.
The expansion means preferably includes six arms, first and second arms being rotatably mounted at one end thereof to an intermediate portion of the lower casing, respectively, the first arm being rotatably connected at the other end thereof to one end of a third arm, the second arm being rotatably connected at the other end thereof to one end of a fourth arm crossing the third arm and rotatably engaged at the intermediate portion of the fourth arm, the other end of the third arm being rotatably connected to one end of a fifth arm, the other end of the fourth arm being rotatably connected to one end of a sixth arm, and the fifth and sixth arms being rotatably mounted at the other ends thereof to the intermediate portion of the top bar.
The fifth and sixth arms can be rotatably mounted at one end thereof to a mounting member, the mounting member being horizontally rotatably mounted to the top bar.
A buffer means is preferably fixed to the lower casing so as to absorb a shock exerted on the lower casing by the expansion means during a folding of the expansion means.
The buffer means preferably includes a leaf spring.
REFERENCES:
patent: 1669052 (1928-05-01), Gusman et al.
patent: 1915944 (1933-06-01), Nagel
patent: 4171592 (1979-10-01), Saitoh
patent: 6191886 (2001-02-01), Sinkoff
Omura Tetsujiro
Seki Kazuharu
Takamoto Hideo
Adams Russell
Cruz Magda
Izumi-Cosmo Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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