an output link member to which the braking cable is connected is pivoted to said base coaxially with said braking lever; a pawl member which is engaged with teeth of a ratchet plate fixedly installed to said base to maintain the braking state is pivoted to the output link member; a transmission link member is disposed between said braking lever and said output link member;

said output link member is pushed by the braking lever through said transmission link member, being turned in one direction from the non-braking position to pull the braking cable connected to the output link member for generation of a braking force;

said transmission link member is pivoted to said output link member such that it is capable of being rocked between the braking position and the releasing position, and has a cam groove which is fitted with a power transmission pin fixedly installed to the braking lever;

said pawl member is capable of being kept energized by a turnover spring disposed between it and said transmission link member in the direction for being engaged with or disengaged from the teeth of said ratchet plate;

the cam groove in said transmission link member has a force transmission cam groove portion which is formed such that, when the transmission link member is in the braking position, the force which is applied to the other end part of said braking lever can be transmitted to said output link member, and a release holding cam groove portion which, when the force applied to said braking lever is removed, and the braking lever is returned by a return spring, causes said transmission link member to be turned to the releasing position, and said turnover spring, which has energized said pawl member in the direction for being engaged with the teeth of said ratchet plate, to be inverted such that said pawl member is energized in the direction for being disengaged from the teeth of said ratchet plate;

said power pin transmission pin and said cam groove are arranged so that when a force is applied to the other end part of the braking lever, the force is applied from the power transmission pin fixed to the braking lever to the force transmission cam groove portion of the cam groove in the transmission link member, and when the braking lever is released, the braking lever tries to return in a releasing direction by a force of the return spring, and the power transmission pin fixed to the braking lever moves from the force transmission cam groove portion to the release holding cam groove portion while the power transmission pin fits in the cam groove in the transmission link member;

when a force is applied to the other end part of said braking lever for pulling the braking cable in accordance with turning of the braking lever to operate the brake, and then the force is removed, the pawl member engages with the teeth of the ratchet plate to maintain the braking state; when the braking lever is displaced in the returning direction by the return spring, the pawl member is brought into the state in which it is energized in the direction for being disengaged from the teeth of said ratchet plate while the braking state being maintained; then, when a force is once applied to the braking lever for releasing the brake, the pawl member is disengaged from the teeth of said ratchet plate; and then when the force is removed, the braking lever and said output link member are turned in the brake releasing direction for releasing the brake.