Abstract: An electric hoist comprising an electric motor and a sheave driven by the electric motor via a reduction gear. The reduction gear comprises a pair of helical gears meshing with each other. One of the helical gears is axially movably arranged on a shaft and is moved in the axial direction thereof when there is a load on the load chain supported by the sheave, and when the axial movement of the movable helical gear is detected by a sensor, the speed of rotation of the electric motor is automatically changed from a higher speed to a lower speed.

Abstract: In an optical disk having an optical recording layer which is capable of having information thereon using a laser beam with information superposed by modulation there is formed a spiral protruding or recessed track having a width equal to about half or less of the wavelength of a laser beam to be used, this track being utilized as the guiding track of the laser beam. A method for manufacturing such an optical disk is also disclosed according to which a recessed track for tracking is formed by plastic deformation of the upper surface of an original disk with a hard processing stylus such as a diamond stylus. The original disk thus produced is utilized for forming an optical recording disk having a protruding or recessed guiding track.

Abstract: In an optical disk having an optical recording layer which is capable of having information thereon using a laser beam with information superposed by modulation there is formed a spiral protruding or recessed track having a width equal to about half or less of the wavelength of a laser beam to be used, this track being utilized as the guiding track of the laser beam. A method for manufacturing such an optical disk is also disclosed according to which a recessed track for tracking is formed by plastic deformation of the upper surface of an original disk with a hard processing stylus such as a diamond stylus. The original disk thus produced is utilized for forming an optical recording disk having a protruding or recessed guiding track.

Abstract: A method of making an optical memory disk and a product thereby comprising the steps of applying a thin tellurium film to a base plate, and of forming an oxidizing layer on the surface of the tellurium by oxidizing treatment of the tellurium film, and an optical memory disk produced by the above-mentioned method.

Abstract: A method of making an optical memory disk and a product thereby comprising the steps of applying a thin tellurium film to a base plate, and of forming an oxidizing layer on the surface of the tellurium by oxidizing treatment of the tellurium film, and an optical memory disk produced by the above-mentioned method.