As is generally well known in the railway industry, when railway cars are taken out of a train and parked at a siding or yard, the handbrake or parking brake on at least some of these cars is applied as a precaution against unwanted or unexpected movement of the cars. A typical railway car hand brake system normally consists of an apparatus for manually applying and biasing one or more brake shoes against the tread of one or more wheels of the railway car by either turning a hand wheel or pumping a ratchet handle on a hand brake mechanism attached to the railway car.
As illustrated in FIGS. 7-9, the hand brake mechanism is usually either a cast or stamped metal gear housing/back plate assembly usually attached to an outside end wall of the railway car and having a rotatable chain drum therein which can be rotated by turning the hand wheel, typically in a clockwise direction. This rotation is transmitted directly through a drive shaft, a pinion, a gear and a chain drum to wind a brake chain onto the chain drum. The other end of the brake chain normally extends through the bottom of the gear housing and is interconnected with cable or other linkage to the brake rigging (not shown) so as to draw the interconnected brake shoes against the tread surfaces of adjacent railway car wheels and, accordingly, apply the hand brake as intended.
When resistance is offered by the chain to further rotation of the hand wheel, such resistance, acting back through the drum, the gear and pinion, causes a nut to move against a ratchet member which is clamped between respective friction surfaces on the nut and on the drive shaft, thus causing the drive shaft, ratchet and the nut to rotate as a unit. A pawl prevents rotation of the ratchet in the opposite direction.
A gradual release of the brakes may be performed by rotating the hand wheel in an opposite direction, such as in a counterclockwise direction, which partially loosens the nut to reduce the clamping force on the ratchet. This action allows the pinion and gear to rotate to reduce chain load and release the brakes.
Although turning the hand wheel in the opposite direction may operate to release the handbrake in proportion to the extent of such turning, some ratchet member and pawl systems may not permit turning the hand wheel in the opposite direction. Accordingly, most handbrake mechanisms are provided with a quick release, non-spin mechanism which functions to instantly and completely release the handbrake without causing the hand wheel or ratchet member to spin. The quick release mechanism is normally actuated by pivoting a handbrake release handle, the handbrake release handle being attached to a brake release shaft, which, when rotated by the hand brake release handle outside of the gear housing, will disengage the chain drum and lock it in place, thereby permitting the chain to self unwind from the chain drum. Normally, the outer end of the brake release shaft is provided with a tight-fitting lever arm type of handbrake release handle so that to release the handbrake, the handle or lever arm is merely pushed upwardly to rotate the brake release shaft (normally clockwise) as necessary to completely release the handbrake.
Whether the handbrake is released via counterclockwise rotation of the hand wheel or by pushing up the quick release lever, both techniques require an operator to climb on and off each car to manually activate this brake release. This can be a time-consuming, as well as, expensive procedure to perform.