Abstract: A tablet comprises a bismuth-based glass and a refractory filler, wherein: (1) the bismuth-based glass comprises, as a glass composition, in terms of mass %, 70 to 90% of Bi2O3, 2 to 12% of B2O3, 0 to 5% of Al2O3, 1 to 15% of ZnO, 0 to 10% of BaO, and 0 to 8% of CuO+Fe2O3; (2) the tablet comprises 1 to 25 vol % of alumina as the refractory filler; and (3) the filling ratio of the tablet is 71% or more.

Abstract: A glass composition for electrode formation includes, as a glass composition expressed in terms of oxides by mass %, 60 to 90% of Bi2O3, 2 to 25% of B2O3, 0 to 25% of ZnO, 0.01 to 20% of MgO+CaO+SrO+BaO, and 0 to 25% of SiO2.

Abstract: Provided is a glass composition for electrode formation including, as a glass composition expressed in terms of oxides by mass %, 73.1 to 90% of Bi2O3, 2 to 14.5% of B2O3, 0 to 25% of ZnO, 0.2 to 20% of MgO+CaO+SrO+BaO (total content of MgO, CaO, SrO, and BaO) , and 0 to 8.5% of SiO2+Al2O3 (total content of SiO2 and Al2O3).

Abstract: A vacuum pump includes rotary shafts connected to a pair of screw-type rotors, respectively, and a pair of shaft retainers extending in the housing. Each shaft retainer supports the corresponding rotary shaft by means of a proximal bearing portion and a distal bearing portion. Each pair of the proximal and distal bearing portions are fixed in the axial direction with respect to the corresponding rotary shaft and shaft retainer. Lubricant oil is stored in an oil storage space in a gear case attached to the housing. A cooling water passage through which cooling water to cool the lubricant oil passes is formed in the gear case. A controller controls the flow rate of the cooling fluid, so that the temperature of the lubricant oil in the oil storage space is kept constant. With this configuration, when the bearing portions are fixed in the axial direction with respect to the rotary shafts and the shaft retainers, it is possible to prevent load from being applied to the bearing portions in the axial direction.

Abstract: A vacuum pump includes a housing assembly having an oil-reservoir chamber in which a lubricating oil is stored; a pair of screw rotors disposed in the housing assembly and engaged with each other; a pair of rotary shafts connected to the rotors, respectively; a plurality of bearings supporting each of the rotary shafts and having an opening; an oil-feed pump for feeding the lubricating oil from the oil-reservoir chamber to the bearing; an oil-circulation passage provided for circulating the lubricating oil from the oil-feed pump to the oil-reservoir chamber through the bearing; a cover provided at the opening of the bearing to close the opening of the bearing with a clearance remained, the cover permitting the lubricating oil to enter the bearing through the clearance; and an oil-escape passage provided adjacent to the bearing for returning to the oil-reservoir chamber the lubricating oil not entering the bearing.

Abstract: A method for controlling the operation of a vacuum pump when stopping the gas transferring operation thereof, the vacuum pump having a housing in which a pump chamber is formed and a gas transferring body which is rotatably disposed in the pump chamber for transferring gas, the method comprises the steps of reducing rotational speed of the gas transferring body to a first preset speed below a second preset speed that is lower than a normal speed of the gas transferring body during normal gas transferring operation of the vacuum pump, maintaining the speed of the gas transferring body below the second preset speed, and stopping the rotation of the gas transferring body when the temperature of the housing reaches a predetermined temperature which is lower than that of the housing during the normal gas transferring operation of the vacuum pump.

Abstract: A vacuum pump includes a housing assembly having an oil-reservoir chamber in which a lubricating oil is stored; a pair of screw rotors disposed in the housing assembly and engaged with each other; a pair of rotary shafts connected to the rotors, respectively; a plurality of bearings supporting each of the rotary shafts and having an opening; an oil-feed pump for feeding the lubricating oil from the oil-reservoir chamber to the bearing; an oil-circulation passage provided for circulating the lubricating oil from the oil-feed pump to the oil-reservoir chamber through the bearing; a cover provided at the opening of the bearing to close the opening of the bearing with a clearance remained, the cover permitting the lubricating oil to enter the bearing through the clearance; and an oil-escape passage provided adjacent to the bearing for returning to the oil-reservoir chamber the lubricating oil not entering the bearing.