A fan blade includes a blade body blowing air and a root portion secured to a support part. A first end part of a fall prevention member is attached to a first mount portion provided in the support part, and a second end part of the fall prevention member is attached to a second mount portion provided in the blade body. A controller controls electric energization to a DC motor to cause the fan blade to stop rotating when the fan blade breaks, the blade body is retained by the fall prevention member, the blade body is tilted, and at least one of a current value or a rotation speed measured by a measurer changes from a predetermined value.
1. A ceiling fan comprising:
a DC motor;
a support part rotated by the DC motor;
a fan blade attached to the support part;
a fall prevention member engaged with the fan blade and the support part;
a controller for controlling electric energization to the DC motor; and
a measurer for measuring at least one of a value of current flowing to the DC motor and a rotation speed of the DC motor, wherein:
the fan blade includes:
a blade body blowing air; and
a root portion secured to the support part,
the fall prevention member includes:
a first end part;
a connecting plate part extending along a longitudinal axis of the fan blade from the first end part; and
a second end part disposed at a distal end of the connecting plate part, the first end part is attached to a first mount portion disposed in the support part, the second end part is attached to a second mount portion disposed on the blade body,
the controller controls the electric energization to the DC motor to cause the fan blade to stop rotating when the fan blade breaks and the blade body is thereby retained to the support part in a tilted position by the fall prevention member such that the tilted blade body thereby causes the at least one of the value of current or the rotation speed measured by the measurer to change from a predetermined value,
the fan blade includes a stress concentrated location on which stress concentrates when the fan blade rotates, the stress concentrated location located between the first mount portion and the second mount portion,
the second mount portion is disposed on the blade body at such a location that a straight line connecting the second mount portion and a rotational axis of the DC motor intersects a straight line connecting the second mount portion and a center of gravity of the fan blade that is in the blade body when the blade body has broken at the stress concentrated location,
the blade body is in an elongated plate shape extending laterally from the root portion,
the root portion includes:
a side plate protruding upward from an upper surface of the blade body and extending along a widthwise axis of the blade body;
an upper plate extending from an upper portion of the side plate toward a center of rotation of the fan blade; and
a lower plate extending from a lower portion of the side plate toward the center of rotation of the fan blade,
a plurality of connecting plates each protruding upward from the upper surface of the blade body and connecting an end of the upper plate and an end of the lower plate,
the upper plate is secured to an upper surface of the support part, and
the blade body includes a plurality of reinforcing portions protruding upward from the upper surface of the blade body and extending from the side plate toward a tip end of the blade body.
2. The ceiling fan according to claim 1 , wherein a clearance gap is provided between (i) the support part and (ii) the side plate, one of the plurality of connecting plates, and the lower plate.