Abstract: An alarm wristwatch comprises a watchcase having a back with an inclined peripheral portion and a watchband attached to the watchcase at opposite sides. A transducer for generating an alarm signal faces a cavity provided in a rear portion of the watch case. A plurality of sound holes provided in the inclined peripheral portion of the watchcase back open into this cavity. The second holes are located within an angle of 45.degree. on either side of the longitudinal center line of the watchband so that they are not blocked or muffled by the arm of the wearer. The cavity and sound holes are so proportioned as to constitute a Helmholz resonator by which the sound produced by the transducer is intensified and efficiently transmitted to the exterior of the watchcase.

Abstract: An alarm watch has an electro-acoustic transducer with a sound releasing cavity containing a vibrating plate for releasing an audible alarm sound. The surface of the vibrating plate exposed to the open air is treated with a water-repellant material having the property to shed or repel water so that when water enters into the sound releasing cavity and wets the vibrating plate, the vibrating plate readily throws off the water thereby obtaining rapid recovery of the alarm sounding function.

Abstract: A miniature electronic buzzer for an electronic watch has two vibrating plates with a sealed space between them forming an air spring. One of the vibrating plates carries an amarature which is acted upon by an electromagnetic to vibrate said plate. Vibration is imparted to the other vibrating plate by the air spring. The two vibrating plates and coupling air spring constitute a vibrating system having two resonant frequencies in the audible range. The electromagnet is energized by current having a frequency in the neighborhood of these resonant frequencies. There may be a third vibrating plate coupled with the second vibrating plate by a second air spring. In this event the vibrating system has three resonant frequencies in the audible range.

Abstract: An electroacoustic transducer particularly for small small-sized portable equipment such as a wristwatch comprises a first vibrating plate which is vibrated by means of an electromagnet and a second vibrating plate which is coupled with the first vibrating plate by an airtight space which acts as an air spring. The first and second vibrating plates have different natural resonant frequencies so that the vibration system comprising the two vibrating plates and the air spring coupling them with one another forms a vibration system having two resonant frequencies. A resonant air chamber superposed on the second vibrating plate has a sound radiating port and has a resonant frequency between the two resonant frequencies of the vibration system comprising the first and second vibrating plates and coupling air spring. The electroacoustic transducer thus responds to a considerable range of frequencies.

Abstract: An electro-acoustic transducer of electromagnetic type is composed of an exciting part having a magnetic core wound with an exciting coil, a vibrating plate provided opposite to the magnetic core at an interval and a ferromagnetic thin plate mounted to the vibrating plate. The thin plate is provided on the surface of the vibrating plate on the side of the magnetic core, so that the thin plate is not exposed to the open air. Furthermore, the thin plate is connected to the vibrating plate at plural points more than three or at a part with some area. Such connection restrains undesirable vibration of the thin plate.

Abstract: Process and apparatus for fabricating a pneumatic rubber fender comprising a cylindrical body of a combination of a plurality of rubber and reinforced rubber layers, both of the terminal ends of which are closed so that compressed air can be sealed therein. In the fabrication process, the cylindrical body of a non-vulcanized rubber fender, one end of which is closed by a first end plate, is firstly formed on a fabrication drum provided with a cylindrical portion and an end plate portion closing one end of the cylindrical portion. The connection of a second end plate with an opened free end of the above-mentioned cylindrical body of the non-vulcanized rubber fender is carried out in such a condition that the above-mentioned opened free end is turned back while the cylindrical body of the non-vulcanized rubber fender is mounted on the fabrication drum.