A medical instrument comprendeº a handpiece (12, 42, 94) º an operative tip (39, 83) connected to said handpiece: a circuit (32, 62) power transmission installed at least partly in said handpiece and operatively connected to said operative tip for supplying power to said characterized operativaº tip because comprendeº one switch device (28, 60, 84, 98) mounted to said handpiece and operatively connected to said circuit (30) to enable automatically supplying power to said operative tip during a movement of said operative tip in a preselected direction relative to said handpiece and to automatically disable the feeding and nergy to said operative tip upon completion of movement of said operative tip in said preselected direction.Un instrumento medico que comprendeº una pieza de mano (12, 42, 94) º una punta operativa (39, 83) conectada a dicha pieza de mano:un circuito (32, 62) de transmision de energia instalado al menos en parte en dicha pieza de mano y conectado operativamente a dicha punta operativa para suministrar energia a dicha punta operativaº caracterizado porque comprendeº un dispositivo de interruptor (28, 60, 84, 98) montado a dicha pieza de mano y conectado operativamente a dicho circuito (30) para habilitar automaticamente la alimentacion de energia a dicha punta operativa durante un movimiento de dicha punta operativa en una direccion preseleccionada con respecto a dicha pieza de mano y para inhabilitar automaticamente la alimentacion de e nergia a dicha punta operativa tras la terminacion del movimiento de dicha punta operativa en dicha direccion preseleccionada.
