The term high security has evolved to encompass manipulation resistant lock mechanism(s) and key control, usually patented. There are a number of different types of high security lock mechanisms. Some incorporate multiple shear lines designed to prevent standard picking/manipulation instruments from...
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The term high security has evolved to encompass manipulation resistant lock mechanism(s) and key control, usually patented. There are a number of different types of high security lock mechanisms. Some incorporate multiple shear lines designed to prevent standard picking/manipulation instruments from successfully operating the locking mechanisms. Some of these high security lock mechanisms require specialized servicing tools. Most high security lock mechanisms incorporate a key that has patent protection or is restricted and after-market key blank manufacturers respect this restriction. Some of the more unique keyways and key cuts require special equipment in order to duplicate or originate keys.
The bottom line is each high security lock mechanism has advantages that can be beneficial for specific types of applications. Locksmiths need to have a broad understanding of the “high security” lock mechanisms in order to recommend the lock mechanism(s) that will provide the optimum level of security, balanced with the end-users requirements and desire for convenience.
The Signature® high security lock mechanism incorporates patented key control and manipulation resistance. In addition, the developers considered the existing SARGENT® key systems during the design process. As a result, the SARGENT Signature lock mechanism is backwards compatible into existing SARGENT key systems.
According to SARGENT, “Signature is available using SARGENT key sections (including H, L, R and others), as well as restricted key sections. The Signature feature provides a solution for upgrading the level of security and key control over unauthorized duplication into existing master key systems.”
SARGENT Signature patent number 5,475,998 incorporates the existing pin tumbler lock mechanism with two additional locking mechanisms, one on each side of the keyway. Each locking mechanism incorporates a spring-loaded lock bar that projects into a locking groove in the shell when the lock mechanisms are in the locked position. The additional lock mechanisms are each controlled by three dimple cuts of varying depths of cuts at varying positions along the keyway into the lower portion of the key blade on each side. The positioning of these cuts and the depths of each cut control the locking bars.
In addition, each plug contains two spring-loaded blocking pins that are designed to prevent non-Signature keys from entering the keyway. These pins are located on each side of the keyway in line with the side pins.
The spring-loaded side pins and blocking pins are factory installed into the plug of each lock cylinder. The side pins and blocking pins are press fit into the plug. They remain within the body of the plug even when the plug is removed from the housing. However, the blocking bars and their springs are not retained into the plug. Care must be taken when removing the plug from the shell.
The tip of each Signature key blade is wedge shaped to permit key insertion when sliding past the blocking and side pins. When a Signature key with the proper bitting and side cut dimples is inserted into the lock cylinder, the pin tumblers align at the shear line and the side pins position themselves within the dimple cuts in the key. The side pins have a recess designed to accommodate the offset ridge on the top of the spring loaded locking bars. When properly aligned, each side pin recess is designed to accommodate the offset ridge and the upper portion of the locking bar. As the key starts to rotate, the locking bars slide into the recesses within the body of the plug clearing the shear line.
When the plug rotates back to the “locked” position, the spring-loaded locking bars extend back into the locking grooves in the shell. When the key is removed from the keyway, the pin tumbler top pins obstruct the shear line. The spring loaded side pins return to the “at rest” position, fixing the position of the locking bars between the side pins and the bottom of the locking groove in the shell.
Lock manufacturers are depended upon to control the issuance of key stock.
High security is a broad term, while key control is a level of security.