Non-excitation operable electromagnetic brake
Provided is a non-excitation operable electromagnetic brake that includes a manually operable rotary cam for switching over a rotor to a brake releasing state, but that allows easy recognition of switchover to the brake released state via an operation reaction force and that also allows reliable keeping of the rotary cam under its acting state. Even when an electromagnet is under a non-excited state, when a rotary cam is rotatably operated to an acting position, an acting portion of the rotary cam slidably operates a rotor via a releasing plate to a brake releasing state against springs. The acting portion of the rotary cam is formed linear along a tangent at a center of the acting portion with respect to a rotary cam rotational direction.
1. A non-excitation operable electromagnetic brake comprising:
a spring for operating a rotor into a braking state;
an electromagnet configured, under an excited state thereof, to operate the rotor into a brake releasing state against the spring; and
a rotary cam manually and rotationally operable between an acting position and a releasing position, wherein in the acting position, the rotary cam is configured to slidably operate the rotor into the brake releasing state against the spring under the non-excited state of the electromagnet and wherein in the releasing position, the rotary cam is configured to release a slidable operation of the rotor into the brake releasing state so that the rotor is operated into the braking state by the spring to allow an operation of the rotor into both the braking state by the spring and the brake releasing state by the electromagnet under the excited state;
wherein in a circumferential cam of the rotary cam, an acting portion thereof corresponding to the acting position is formed linear along a tangent at a center of the acting portion with respect to a rotary cam rotational direction,
wherein the non-excitation operable electromagnetic brake further comprises a rotation restriction portion configured to restrict rotation of the rotary cam from the releasing position in a rotational direction opposite to a set rotational direction which is set for switching the rotary cam from the releasing position to the acting position.
2. The non-excitation operable electromagnetic brake of claim 1 , wherein the rotation restriction portion is configured to come into contact with the rotary cam.
3. The non-excitation operable electromagnetic brake of claim 1 , further comprising a positioning mechanism capable of switchover between a positioning state for fixedly positioning an operational tool for rotating the rotary cam to operational positions corresponding respectively to the releasing position and the acting position and a position releasing state for allowing an operation of the operational tool.
4. The non-excitation operable electromagnetic brake of claim 3 , wherein:
the positioning mechanism includes an engaging portion protruding from the operational tool and a positioning portion provided at a portion opposed to the engaging portion;
the positioning portion includes a first receded portion for positioning the operational tool at the acting position and a second receded portion for positioning the operational tool at the releasing position; and
positioning of the operational tool is provided by engagement of the engaging portion in the first receded portion or the second receded portion.
5. The non-excitation operable electromagnetic brake of claim 3 , wherein the positioning mechanism further includes an urging portion for urging to maintain the positioned state, wherein a change of the positioning mechanism from the positioning state to the position releasing state is made against an urging force of the urging portion.