Abstract: A fluid-driven medical or dental handheld device includes a head, the head including a housing and a impeller rotatably mounted in the housing. The housing defines a receiving chamber for receiving the impeller, a main air inlet and an air outlet being defined in the housing and communicating with the receiving chamber. An inner surface of the housing surrounding the receiving chamber defines a plurality of grooves, the grooves being arranged at intervals along a circumferential direction of the housing. The grooves reflect rotating airflows directed to the grooves to change directions and speeds of the airflows to form interference airflows, which can effectively reduce the rotation speed of the head at idling, while ensuring the torque output of the head during grinding teeth.

Abstract: A dental handpiece includes a barrel, an air turbine, a central shaft, a bearing and a seal. The barrel includes an axial open end. The air turbine is rotatably provided in the barrel. The central shaft is secured to the air turbine to rotate with the air turbine. The bearing is mounted in the barrel and supports the central shaft for rotation. The seal is trumpet-shaped and arranged between the open end of the barrel and the bearing. The seal includes a sealing portion sleeved over an outer cylindrical surface of the central shaft. The sealing portion is deformable to separate from the outer cylindrical surface of the central shaft or closely contact the outer cylindrical surface of the central shaft depending on a pressure difference between interior and exterior of the barrel.

Abstract: A fluid-driven medical or dental handheld device includes a head, the head including a housing and a impeller rotatably mounted in the housing. The housing defines a receiving chamber for receiving the impeller, a main air inlet and an air outlet being defined in the housing and communicating with the receiving chamber. An inner surface of the housing surrounding the receiving chamber defines a plurality of grooves, the grooves being arranged at intervals along a circumferential direction of the housing. The grooves reflect rotating airflows directed to the grooves to change directions and speeds of the airflows to form interference airflows, which can effectively reduce the rotation speed of the head at idling, while ensuring the torque output of the head during grinding teeth.