To improve negative pressure chamber airtighness by applying the constitution that a hard synthetic resin is used for forming a housing and a rod, as well as a soft thermoplastic plastic elastic material for forming a diaphragm and, then, the housing and the diaphragm as well as the diaphragm and the rod are jointed to each other at a thermal fusing process.
A housing 1 is formed as a hollow and approximately spherical body and made of such material as hard synthetic resin, polycarbonate, nylon 11 having upper and lower half-split bodies integrated with each other via a thermal fusion surface 9a. In addition, the housing 1 has a pipeline 12 at the upper part and a loose insertion hole 15 for passing a rod 6. Also, a diaphragm 2 is formed so that a thermoplastic elastic material softer than the hard synthetic resin of a hollow disc body and different therefrom in quality, such as hydroliquefied SBS block copolymer and olefin elastomer is bent in a projected state along the outer part, and integrated with the housing 1 via a thermal fusion surface 8a at the outer end. Also, the inner end is integrally formed via a thermal fusion surface 8b at both ends of the horizontal part of a T-shaped rod 6 made of a hard synthetic resin. According to this construction, the airtightness of a negative pressure chamber 3 is improved.
TOKUNAGA MASAHIRO
MURATA YUICHI
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