Apparatus for raising and lowering the lower screen mask in a mo

Optical: systems and elements – Projection screen – Border – mask – shade – or curtain

Patent

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Details

352 43, 352 69, G03B 2156, G03B 3700

Patent

active

051219778

ABSTRACT:
The device described here allows for the raising or lowering of the mask which sits along the bottom edge of the screen in a motion picture theater and, along with the top and two side masks, frames the entire screen. The lower mask is supported by a number of support units, each containing two arms, equal in length and pivotally joined at their apex, where they are also attached to the bar that supports the screen mask. The arms are moved further apart or closer together at their lower ends, so that they push the bar supporting the screen mask up or down. A rotating shaft, with sections of oppositely-pitched threads, is connected to a motor. Sleeves with complimentary inside threads are pivotally mounted to the support arms, such that rotation of the motor in one direction moves the loser ends of the arms further apart and rotation in the other direction brings the lower ends of the arms closer together. Thus, the screen mask can be raised or lowered by motor rotation in one direction or the other. To ensure that the lower ends of the arms move only along the desired pathway, roller bearings are mounted to the sleeves housing the inside threads which complement the threaded rods. These roller bearings move on a fixed track, in the same direction as the sleeve, and tightly enough to support the weight of the entire apparatus. This track is mounted to the floor. This system can be operated manually or automatically, in response to signals applied to the film, which direct the motor (or motors) to turn a precise number of rotations in the desired direction.

REFERENCES:
patent: 490482 (1893-01-01), MacKaye
patent: 1200845 (1916-10-01), Johnson
patent: 1734467 (1929-11-01), Howard
patent: 1857673 (1932-05-01), Vallen
patent: 1882828 (1932-10-01), Hall et al.
patent: 1904963 (1933-04-01), Vallen
patent: 1954656 (1934-04-01), Vallen
patent: 3475086 (1969-10-01), Vetter
patent: 3502402 (1970-03-01), Markson
patent: 4915496 (1990-04-01), Stine

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