Abstract: A fire safety transmission apparatus comprising an explosion-proof container, an adapter plate secured to the container, a cylindrical sleeve mounted to the adapter plate defining a central bore, allowing communication with the interior of the container. The sleeve bore is stepped, defining seats for a plurality of ball bearing races mounted therein. A rotatable stepped shaft having a diameter adapted to fit within the central bore rests on the ball bearing races. The shaft is connected to a motor mounted in the explosion-proof container with the spacing defined between the inner wall of the cylindrical sleeve and the outer surface of the freely rotating shaft being sized a predetermined tolerance for a predetermined length sufficient to prevent a flame from passing therethrough.

Abstract: A fire safety transmission apparatus comprising an explosion-proof container, an adapter plate secured to the container, a cylindrical sleeve mounted to the adapter plate defining a central bore, allowing communication with the interior of the container. The sleeve bore is stepped, defining seats for a plurality of ball bearing races mounted therein. A rotatable stepped shaft having a diameter adapted to fit within the central bore rests on the ball bearing races. The shaft is connected to a motor mounted in the explosion-proof container with the spacing defined between the inner wall of the cylindrical sleeve and the outer surface of the freely rotating shaft being sized a predetermined tolerance for a predetermined length sufficient to prevent a flame from passing therethrough.