Abstract: The present invention prevents cracking of a brake shoe even when the sliding surface of the brake shoe is heated to a high temperature and provides high reliability. The present invention provides a brake shoe for elevator emergency stop which generates a braking force by pressing brake shoes against a guide rail and making the brake shoes 5 slide to stop an elevator cage in the event of anomalies, including the brake shoes made of a cast iron material having a plurality of grooves 3 formed in a direction substantially perpendicular to the guide rail and gear teeth which constitute a sliding surface with the brake shoes 5 formed as gaps between the grooves, wherein the depth of the grooves is 3 mm or more and not more than 1.7 times the width of the gear teeth.

Abstract: An image to be projected is deformed to obtain a projected image having small distortion. An image deforming device constituted by an optical fiber bundle is arranged in front of an original of a projector arranged at a position other than the center of a dome, so that the image of the original is transmitted from an end face on the incident side of an image correction device to an end face on the emission side as images divided into pixels using optical fibers as units. A secondary image subjected to predetermined deformation is displayed on the end face on the emission side, and the secondary image is projected on a dome surface to obtain a projected image which is free from distortion by the same manner as that performed when the original is projected from the center of the dome onto the same projection surface.

Abstract: A non-electrification polymeric composite material composed of a tetrafluoroethylene/fluoro(alkyl vinyl ether) copolymer containing 4% by weight or more fluoro(alkyl vinyl ether) and an electrically conductive material.This non-electrification polymeric composite material is suitably used in a holder for holding a semiconductor substrate, or the like.

Abstract: A fluorine-containing copolymer comprising monomeric units of:(a) tetrafluoroethylene,(b) 8 to 15% by weight of hexafluoropropene on the basis of the weight of the copolymer, and(c) 0.2 to 2% by weight of a fluoroalkyl vinyl ether of the formula:CF.sub.2 .dbd.CF--O--(CF.sub.2).sub.n --CF.sub.2 Xwherein X is hydrogen or fluorine, and n is an integer of 3 to 9, on the basis of the weight of the copolymer, which has good moldability and improved stress crack resistance and flex resistance when formed as an article such as a film.

Abstract: A fluorine-containing copolymer comprising monomeric units of(a) tetrafluoroethylene,(b) 8 to 15% by weight of hexafluoropropene on the basis of the weight of the copolymer, and(c) 0.2 to 2% by weight of a fluoroalkyl vinyl ether of the formula:CF.sub.2 .dbd.CF--O--(CF.sub.2).sub.n --CF.sub.2 X (I)wherein X is hydrogen or fluorine, and n is an integer of 3 to 9 on the basis of the weight of the copolymer, which has improved stress crack resistance, and flex resistance as well as good moldability.

Abstract: A process for preparing a tetrafluoroethylene/fluoro(alkyl vinyl ether) copolymer comprising polymerizing tetrafluoroethylene and fluoro(alkyl vinyl ether) in an aqueous suspension system which comprises a mixed medium of water and a fluorohydrocarbon or a chlorofluorohydrocarbon in a volume ratio of from 1:1 to 10:1 at a temperature of from 0.degree. to 25.degree. C. in the presence of a polymerization initiator of the formula:[Cl(CF.sub.2).sub.n --COO].sub.2 (I)wherein n is an integer of 1 to 10, the copolymer obtained by the process having a small number of unstable terminal groups and excellent flex life.