A dynamic-braking apparatus adapted to halt film movement in a microfilm viewer such that individual film frames may be easily selected. Particularly useful at high-film speeds, this braking apparatus comprises a pulley to receive braking torque and a weight which is connected to the pulley by a torsion spring. The braking force on the pulley is opposed by the inertial force of the weight, causing end displacement of the spring, resulting in its contraction and its transmission of braking torque to the shaft from which the film is being fed. The degree and rate of brake torque transmission are further controlled by means of a further connection between the pulley and the weight which allows only limited relative movement between the parts. Compression springs are provided to prevent "noise" and to insure return of the torsion spring to an equilibrium position.
In a braking system for an intermittent driving mechanism, a braking shoe is arranged for engaging the outer one of two flexible braking rings loosely surrounding a braking drum, a braking finger fast with the braking drum loosely engaging between said braking rings, the braking shoe being mounted at one end of a pivoted braking arm, the other end of which is engageable with a pivoted catch and release member operable by an electro magnet.
A wheel brake assembly for shopping carts is characterized by a hub adapted for rotation about an axis, a coil spring coaxially mounted on the hub, and a pair of annular disks coaxially mounted on the spring. One of the disks is stationary and has one end of the spring connected therewith. The other disk is rotatable and has the other end of the spring connected therewith. Rotation of the rotatable disk in one direction to a braking position draws the spring ends together so that the coil spring constricts on the hub to prevent rotation of the hub about the axis. Rotation of the rotatable disk in the other direction to a release position pushes the spring ends apart to relax the coil spring and allow the hub to rotate.
