The Principle of How Padlocks Work

by Robert Fox

Padlocks come in different sizes, shapes, and colors, and they are used to keep our belongings safe from thieves and burglars. Padlocks have been used for thousands of years with a few changes in the complexity of their blueprint or design by various civilizations and people depending upon the process of construction and technology available. Nevertheless, all the past locks have a unique shaped key that releases the internal mechanism and unlocks the instrument.

The Principle of How Padlocks Work
The Principle of How Padlocks Work

The Invention of Locks

  • The first lock was made completely from wood in ancient times in Egypt. The Egyptian locks date back to 4000 years that making it into 2000BCE.
  • In 1778 Robert Barron made a new lock system called double-acting locks.
  • Joseph Bramah is a creative English inventor. He patents a high-security lock called a Bramah lock. A prize of 200 guineas was to be presented to the winner who would be successful in cracking the lock. As claimed by Bramah company Joseph Bramah's ideas were "Fifty years forth of some Chubb lock and seventy years leading of Yale."
  • Jeremiah Chubb in 1818 invented a detector lock that seizes up if anybody attempts to open it. The jam makes it obvious that the lock has been intruded.
  • Edwin Cotterill in 1846 developed an "unpickable" and "power proof" lock named as Climate Detector bolt. This lock has been manufactured using some variation of Joseph Bramah lock design.
  • James Sargent in 1857 invented a combination lock that has a numeric combination that can only be changed with a unique key. And it was a bank safe time lock that opens only at a specific time.
  • Linus Yale Jr. in the 1860s invented a convenient design of Yale pin tumbler lock that is equipped with a cylindrical pit/hole inside which metal pin or plug is housed. The lock is known as a Cylinder lock.
  • A security advanced padlock was designed by Harry Soref in 1924. He was the creator of the Master locks company and was known as a master locksmith.

The Padlock

After the industrialization all over the world, the padlocks started to mass-produce and eventually comes the advanced design of the pin tumbler lock. A padlock has a pin tumbler outline/design and this design is called pin tumbler because the inside of the lock has several pins along with a barrel. The tumbling or rotating of the barrel resulted in the name pin tumbler padlock.

The padlock has robust mechanical locks that are effortless to assemble. These padlocks are being used for almost everything, for instance, locking bikes, locking doors, and even locking the eternal love between a couple on a symbolic bridge by throwing away the key to ensure the love cannot be undone. The cheap padlocks can be undone without their specific key if someone knows how to unlock them. The advanced and expensive padlocks are hard to be unlocked because of the complex mechanism.

How a Padlock Works

How a Padlock Works
How a Padlock Works

Shackles

Shackles
Shackles

At first glance, the most observable feature of a lock is its U-shaped shackle on the top. When the lock is open the endpoint of a shackle comes out of principal body allowing it to rotate easily. The inside of a shackle has two notches that form the lock operation or mechanism.

Locking Mechanism

Locking Mechanism
Locking Mechanism

To bolt the lock we just align the openable shackle end with the cavity in the main body and shove them together. Then locking makes you feel the engaging of the inner locking system that clicks into the position that results in the moving shackle being at a loss to withdraw from the main body. To unlock it a key specific for the lock is inserted at the place in the base of the body. By rotating the key the shackles get released.

Plug

Plug
Plug

While looking inside the body of the padlock we can observe the whole locking mechanism which consists of the plug and grooves. When a key is inserted into the lock it slides inside a plug that is linked with the grooves. The plug of a lock has numerous holes and within every hole, a little metal cylinder is present which is called a key pin.

Grooves

The grooves make sure of a smooth transition of the key inside the lock. When the specific key for the lock is turned it rotates the plug.

Key Pins

Every key pin has a contrasting height that is compatible with the special key profile.

Chambers

Within the compartments of a lock, various chambers are aligned per the holes present upon the plug of the lock. In each chamber, there is a spring that functions to push another pin which is known to be the driver pin.

The driver pin is pushed by the spring into a corresponding hole present in the plug till it meets the key pin. All this makes sure that a driver pin stays adjoining the pin key even if the padlock's spin upside down.

Shear line

The intersecting point between the lock casing and the plug is called a shear line. When the key is not installed the driver pin stays partway in the chamber and partway inside the plug that means the locks' plug cannot be rotated.

When we insert a key inside a lock, the mechanism of matching between the key pins and key profiles starts with the upwards and downward movement till the key's fully installed. When the right key is completely inserted then the alignment of the top part of every key pin with a shear line happens.

The locks' driver pin is then pushed upward with is being completely inserted inside the housing during which the key pin sits completely inside the plug ensuring that the plug will be able to revolve. Suppose an unsuitable key is being used inside a lock then this will result in mismatch or incompatibility of key pins followed by no rotation of the plug.

6th Chamber

6th Chamber
6th Chamber

There are six spring chambers inside the lock but the key only uses five of them to form a lock. The sixth driver pin settles inside the deep or extensive groove and it's not utilized by a key. In lieu, this driver pin prevents the pulling of the plug through the body lock. It happens because the driver pin stays engaged inside the groove even in a locked or unlocked situation.

6th Pin

The sixth pin always sits inside the groove and functions to prevent the pulling out of the plug.

With the right key, we can move the plug but we have to ensure that the shackle couldn't be removed in absence of the right key while we are trying to release the locks' shackle.

Cam

On the ending point of a plug, there is a cam which is simply a bit of metal. A cam extends the plug's body and it has a shape that permits it to function as a leaver.

The Latches

The Latches
The Latches

Adjoining the cam, there's a latch positioned on each side of it. The outermost end of a latch is angled and it fits within the shackles' notches. A spring is settled within the lock that pushes against every latch compelling it forth. This is followed by the forcing of angled edges inside the notch. The interconnecting of the notch and latch forstalls the pulling out of the shackle.

Springs

The innermost/deepest end of every latch possesses a little arm that expands out and lies with a flat border of a cam. Each latch lies against the bottom and top. With the rotation of the cam, its shapes result in the inside pulling of latch arms. The arms get detached through the notches.

Arm

At this moment the shackle could be lifted. And it is made much easier with a spring that is positioned under the extended end of a shackle inside the main lock body. The spring will shove the shackle out and that will make it simple to use. This also lets us observe visually if the bolt is locked or unlocked.


About Robert Fox

Rob Fox is a former hydro worker, who used to teach self defence in Miami for 10 years. His hobbies include cribbage, golf, locksmithing, and cooking.

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