Padlock

Padlock (1720)

                                      Polhem devises a portable lock that effectively resists tampering.

 Introduction

                 Primitive padlocks have been come around since medieval times, but their design left them prone to force or picking. In 1720, Swedish inventor CHRISTOPHER POLHEM (1661-1751) conjured up a lock that was much more resistant to the dexterous hands of lockpickers.

 Information                                           

Polhem was one of the most gifted mechanical engineer of his day. After study mathematics, physics and engineering at Uppsala University, he set up a clock repairer. His ingenuity was soon spotted by important patrons, including King Charles XI of Sweden. Polhem went on to design many intricate devices both small (watch mechanisms) and large (industrial Machinery). Perhaps his most enduring invention, however, was the PADLOCK. His basic design comprises an elliptical cast iron body containing a series of rotating disk. When locked, the disks fit in to grooves on the shackle (the U-shaped bar on the top of the padlock), preventing its release from the body. Notches on the discs can be aligned with those on the shackle by rotating the correct key, thus releasing the shackle and allowing the lock to be opened.

                                     The Swedish inventor’s device became known as pohlem lock, or Scandinavian lock, and polhem started a factory in Stjarnsund to produce it. The pohlem lock came to dominate the market. The design was later strengthened by the American locksmith HARRY SOREF, who founded the Master Lock company in 1921. A modified version of this design is still in use today.