Mechanically driven screw supercharger

Claim 1

A mechanically driven screw supercharger comprising: (a) a casing and (b) a set of meshing male and female screw rotors rotatably supported in said casing; wherein: (c) said set of meshing male and female screw rotors has an input shaft; (d) said casing has a through hole formed in a wall thereof at a position corresponding to said input shaft or on the extension of the axis of said input shaft. (e) a bearing supporting boss is formed around said through hole so as to project outwardly from said casing; (f) a bearing is mounted on the external surface of said bearing supporting boss; (g) a driven power transmitting member is journaled on said bearing; (h) said driven power transmitting member is adapted to be driven by a prime mover and having a central boss projecting into said bearing supporting boss; (i) said input shaft is coupled to said central boss of said driven power transmitting member; (j) said casing has a main discharge port in fluid communication with a suction passage and an auxiliary discharge port upstream from said main discharge port; and (k) said auxiliary discharge port is connected to a three-way switching valve, one outlet port of which is connected to said suction passage downstream of said main discharge port and one outlet port of which is connected to a relief valve.