Abstract: An improved structure of an impact screwdriver is provided which achieves a low-noise screw-driving operation. The impact screwdriver includes a clutch assembly for transmitting torque provided by a motor to a tool bit. The clutch assembly includes a toque-transmitting member, a torque-outputting member, and a clutch coil spring. The clutch coil spring is selectively wound around the torque-transmitting member and the torque-outputting member according to a rotational difference therebetween to establish torque transmission for providing the torque to the tool bit intermittently.

Abstract: To charge a battery having a different number of cells connected in series with a relevant charge current, the number of cells of the battery is firstly determined and a current level corresponding to the number of cells is determined in view of the potential of the charger. The charge current having a level substantially equal to the thus determined current level is flowed in the battery.

Abstract: New compound, designated as leucanicidin, is now provided and is useful as insecticide. Leucanicidin is fermentatively produced by a microorganism Streptomyces halstedii No. 3002-14, (FEKM BP-493).

Abstract: A vacuum pump includes a rotatable cylinder rotatably disposed coaxially around an inner stationary cylinder and in an outer stationary cylinder. The rotatable cylinder has a plurality of recesses defined in inner and outer circumferential surfaces thereof. The outer stationary cylinder has a helical groove defined in an inner circumferential surface thereof. The inner stationary cylinder has a helical groove defined in an outer circumferential thereof. The rotatable cylinder is rotated by a motor to deliver a gas axially along the helical grooves. The recesses are effective to produce turbulent flows in the gas to increase the rate at which the gas is discharged. The recesses have an axial length smaller than the transverse width of helical threads on the outer circumferential surface of the inner stationary cylinder and the inner circumferential surface of the outer stationary cylinder, to minimize any gas leakage across the helical threads.

Abstract: A molecular drag pump for delivering a gas under molecular flow conditions comprises a pair of parallel, helically threaded rotors rotatably mounted in a stationary housing. The rotors have respective helical threads and respective helical grooves, and are held in close mesh with each other. The helical threads are helically inclined in one direction to the axes of the rotors, and have a flank angle such that the helical threads are closely received in the respective helical grooves while keeping the threads out of contact with each other. The rotors are rotated in one direction about their respective axes to move a gas introduced through an inlet port toward an exhaust port axially along the rotors.

Abstract: New compound, designated as leucanicidin, is now provided and is useful as insecticide. Leucanicidin is fermentatively produced by a microorganism Streptomyces halstedii No. 3002-14 (identifiable as FERM BP-493).