Abstract: The present invention relates to a diaphragm for sound generating devices and a preparation method thereof, and a sound generating device. The diaphragm for sound generating devices comprises only one layer of a thermoplastic polyester elastomer film, wherein the thermoplastic polyester elastomer is formed by copolymerization of a polyester hard segment which is prepared by reacting an aromatic dicarboxylic acid with a dihydric alcohol and a soft segment containing an aliphatic polycarbonate, and the diaphragm has a thickness of 10-200 ?m , and a loss factor of 0.1-0.3 at a temperature of 23° C. The thermoplastic polyester elastomer used for the diaphragm of the present invention is composed of the polyester hard segment and the aliphatic polycarbonate soft segment, and such material not only solves the problem that the existing thermoplastic elastomers have poor resistances to high temperatures and chemicals, but also has the advantages of improving sensitivity etc.

Abstract: The present invention relates to a diaphragm for sound generating devices and a preparation method thereof, and a sound generating device. The diaphragm for sound generating devices comprises only one layer of a thermoplastic polyester elastomer film, wherein the thermoplastic polyester elastomer is formed by copolymerization of a polyester hard segment which is prepared by reacting an aromatic dicarboxylic acid with a dihydric alcohol and a soft segment containing an aliphatic polycarbonate, and the diaphragm has a thickness of 10-200 ?m, and a loss factor of 0.1-0.3 at a temperature of 23° C.

Abstract: A type of dual speed vertical hydraulic jack, including pedestal featuring hydraulic control pressure regulating assembly and oil drain valve assembly; jacket, hydraulic cylinder and pump body fixed on pedestal; oil storage cavity formed between jacket and hydraulic cylinder; piston rod with piston assembly at bottom; top cap, pump core, button, first oil path and second oil path; on bottom of said pump core, a step is provided and constitutes sealing with inner wall of pump cavity, third oil path and fourth oil path are provided on the step respectively, first steel ball valve and second steel ball valve that control connection and disconnection of said pump cavity with third oil path and fourth oil path respectively are provided on these oil paths, and at lower part of pump core, a fifth oil path is provided for connecting third oil path with upper cavity of pump cavity.