Commercial locks are designed to limit the types of keys that can enter the lock cylinder. This is accomplished by uniquely slotting the plug component within the lock cylinder. This unique slot is the “keyway.” The keyway allows a predictable subset of different key shapes to be properly...
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Figure 6 is a Schlage multiplex key system that features a “composite” keyway that all single-section key blanks can access.
A composite keyway is enlarged to accept more than one key section. This provides for an additional level of master keying. Composite keyways should be used in areas where low security is required.
A practical example using this level is where restrooms in all buildings would be keyed alike and locks would feature composite keyways. Any custodian in any building could open or close a restroom in any building.
Note that the keyways in Figure 6 are identified as “obverse” keyways. Obverse or open keyways are those that are available without ordering formalities. This means that these are available to all locksmiths, directly from their distributors, without questions asked.
Here is a practical example of how a locksmith can use obverse keyways. A client has a site with 90 suites, all keyed to a master key. The client wants a new administration suite keyed off the master key, but still the manager needs to carry a single key. If all the suites use a “C” keyway, the administration suite can be keyed using “E” keyway lock cylinders and a new master key cut for the manager on an “CE” key blank. Although the CE is not considered a master key, the use of the CE provides greater expansion capability by reserving the “H” key blank. The new master key will open all suites including the new administration suite.
This multiplex key system in Figure 7 was introduced in 1959 and incorporates the single-section keyway 60, which replaced 77 as Corbin's stock keyway in 1960.
It is common that different families of key sections will mirror other existing key sections. Figure 8 is an example where broaching and milling tools were reversed to produce one family of keyways for one company and an opposite for the other. This is preferred as development of new key sections relies on new sets of tools which are expensive to originate.
Protecting Key Stock
The inherent weakness of master key systems is the availability of others to obtain key stock. As master key systems are enhanced by multiplexing; protecting key stock becomes especially important.
Lock companies are sensitive to this and provide multiplex key systems with different levels of key control. Open (or obverse) systems allow any locksmith to obtain key stock; restricted systems are controlled by the company or distributor; and security systems require special arrangements between company and customer to obtain key stock.
There was a time in which companies that provide key stock to locksmiths would not provide key blanks identified by lock companies as restricted. Starting in the late 60s, key shops started carrying aftermarket key blanks for older restrictive systems. By the late 70s it was common place to see popular restrictive key blanks in key shops.
A typical means for lock companies to protect the ornamentality of a key blank is to protect it with a design patent. In an effort to protect the keyway, lock companies started including the keyway profile in the design patent.
Functionality vs. Ornamentality
In 1996, Best Lock had their design patent 327,636 made invalid.
Best Lock started a campaign in which they initiated individual design patents for 33 original keyways. In this manner the keyways could not be reproduced for aftermarket use.
Best Lock sued Ilco-Unican Corp., when the company distributed aftermarket key blanks with similar keyways. Best Lock lost the lawsuit when the design patent that protected the keyways was made invalid. The court decided that the profile of the keyway was much more functional than ornamental. Design patents protect the ornamentality of the invention. Where an invention can be ornamental and functional, keyways are very specific and based almost entirely on being functional.
Best Lock's submittals were very specific. The title of each design patent was: “the portion of a key blank” (basically the keyway), and claims focused on the precise shape. This was all about functionality.
Sectional and related keyways developed by SARGENT to meet large institutions demands.
ASSA Twin Series lock mechanisms designed for single step master keying.