A locking pulley is a type of pulley that will lock the cord in place when the cord is manipulated correctly. This pulley is primarily found on household window blinds in the consumer market, but it also has some limited commercial and boating uses. The locking pulley is a simple pulley, except with two wheels instead of one. When the cord is pulled outward, it moves one of the wheels, causing the entire mechanism to lock. This enables the user to keep the blinds, or whatever object is attached to the pulley, in place without holding the cord.
A simple pulley consists of one wheel with a cord threaded through the wheel. When the operator pulls one end of the cord, the object on the other end lifts. The main difference between the locking pulley and simple pulley is that the second wheel enables the locking function.
With a locking pulley, the same basic mechanics are used, but the operator can lock the cord in place and can walk away, leaving the object suspended. This is done by pushing the larger of the two wheels out of place by pulling the cord toward the right or outside. When this wheel comes out of place, the smaller wheel falls forward and the wheels pinch the cord to trigger the lock.
Unlocking a locking pulley is done in reverse. The operator pulls the cord toward the inside, or left, of the pulley. This pulls the small wheel back into alignment and the larger wheel falls back to its original position, releasing the cord.
The use of locking pulleys has mostly been in the consumer sector. Common household blinds use this mechanism so operators can lift the blinds to let the sun in. There has been some limited commercial and boating use of locking pulleys, but other pulley types are usually used for those purposes.
While a locking pulley is convenient because it allows the operator to keep the cord in a certain position, it also has a few problems. If the locking mechanism is used frequently, it can shred the cord, because the large wheel has teeth on it. They have more moving parts and require force to lock the pulley into place, so they can fall apart quicker than other pulleys. Some people also may find locking and unlocking the pulley to be difficult, because the cord has to be pulled in a certain way to get the mechanism to work.