Abstract: An arrangement for driving a rotary dental or medical tool attached to a handpiece includes a vane motor that is compact enough to be mounted within the head of the handpiece. The vane motor includes a rotor, which is mounted within an eccentric bore of a cylinder, which forms a stator. Inlet ports into the vane motor preferably open perpendicular to the rotor's axis of rotation so that intake air is directed substantially directly at the vanes. An arrangement of the inlet and of outlet ports allows a duty stroke for each vane up to 240 degrees. Inlet and exhaust air preferably enters and exits the vane motor via annular channels surrounding either end of the cylinder. There is then no need to align the motor angularly when it is installed in the head. A radial gap is preferably provided between the rotor and the shaft it is mounted on. Channels connecting the bottom of each vane slot with this gap reduce the vacuum effect acting on the vanes as they extend.

Abstract: A dental abrasion arrangement includes a pressure vessel that has an inlet port and an outlet port. A source of pressurized propellant gas is attached to the inlet port and a dental abrasion tool is attached to an outlet port of the pressure vessel. Abrasive powder is ejected from the pressure vessel and to the abrasion tool via a discharge assembly and the outlet port. A feeding and metering auger is mounted within the pressure vessel. The auger is mounted substantially horizontally within the pressure vessel. The auger is driven by a motor, so that the abrasive powder within the pressure vessel is fed to the discharge assembly as the motor causes the auger to rotate.

Abstract: A pressurized feeder vessel feeds powdered material into a stream of propellant gas. The feeder vessel includes a funnel-shaped hopper that is resiliently suspended by an elastic member inside the vessel. A vibrator such as an electric motor with an eccentric weight on its shaft vibrates the bottom end of the hopper. The vibration forces of the vibrator are preferably transferred to the hopper via a flexible diaphragm. The hopper is thus subjected to primary vibration forces and torques from below, and secondary, reaction vibration forces and torques from above. This induces the powder in the hopper to fluidize thoroughly and to circulate. In particular, it circulates over and past an inlet orifice, through which powder exits the hopper and enters the propellant stream. Powder circulation thus also prevents clogging of the inlet orifice and leads to more even flow rates. The invention is particularly well suited for delivering abrasive powder to a hand-held dental tool for abrasive treatment of teeth.