Abstract: An air-compressing apparatus has four compressors individually supplying compressed air to a tank having a pressure sensor. The pressure sensor is connected to control circuits of the compressors. The control circuits compute times needed for the tank pressure to reach minimum and maximum pressures, respectively, of the tank by using the detected tank pressure and also using a tank pressure change value. The computed time values correspond to the consumption of compressed air. Thus, the control circuits can control the number of compressors to be operated according to the consumption of compressed air.

Abstract: An air-compressing apparatus has four compressors individually supplying compressed air to a tank having a pressure sensor. The pressure sensor is connected to control circuits of the compressors. The control circuits compute times needed for the tank pressure to reach minimum and maximum pressures, respectively, of the tank by using the detected tank pressure and also using a tank pressure change value. The computed time values correspond to the consumption of compressed air. Thus, the control circuits can control the number of compressors to be operated according to the consumption of compressed air.

Abstract: A method for demineralizing water or an aqueous solution, which comprises contacting the water or the aqueous solution to be treated to a strongly basic anion exchanger made of a crosslinked polymer having a constituting unit of the following formula (I): ##STR1## wherein A is a C.sub.1-2 linear alkylene group, B is a C.sub.4-8 linear alkylene group, each of R1, R2 and R3 which may be the same or different, is a C.sub.1-4 alkyl group or a C.sub.2-4 alkanol group, X is a counter ion coordinated on the ammonium group, and the benzene ring D may have an alkyl group or a halogen atom as a substituent.

Abstract: A scroll fluid apparatus has a revolving scroll and an auxiliary crank as a rotation prevention mechanism. The revolving scroll has a two-layer structure including an auxiliary member having an annular plate portion, and an end plate member having an end plate, the two members being superposed axially. A positioning mechanism is provided between the auxiliary member and the end plate member to position and unite them in a circumferential direction. When the end plate member expands radially due to a rise in temperature, the end plate is displaced radially while being in sliding contact with the annular plate portion. The end plate is fastened to the annular plate portion through a bolt portion at the center thereof, where the amount of radial displacement due to the thermal expansion is the smallest. Accordingly the annular plate portion is not displaced radially and thus, no radial load acts on the auxiliary crank.