Medeco: Angled Cuts and Rotating Pins

Origins

Medeco's name comes from Mechanical Development Company, a machine shop in the Salem area. Medeco's own 50th-anniversary release (2018) says engineer Roy Spain ran the shop and invented a locking cylinder with a key that had "unique angled cuts." Spain and his partners later applied for a utility patent and began selling the lock under the shortened name. The company dates its start as a lock maker to 1968, the year its own materials give for the first Medeco cylinder.

Sources disagree on when the original machine shop opened. One account gives 1950, another the mid-1950s, and a regional economic-development profile simply says 1968. This article does not give a date for the shop.

The 1970 Patent

U.S. Patent 3,499,302, "Cylinder Lock," was filed March 1, 1967 and granted March 10, 1970. Four inventors are named, all of Salem, Virginia: Roy C. Spain, Roy N. Oliver, Elvis C. Flora, and Paul A. Powell. The abstract sets out the core idea:

• The key is "cut at three different levels and cut at three different angles."
• Each tumbler in the plug is positioned "reciprocally to clear the shear line" and also "positioned rotationally."
• Once the tumblers are both lifted and turned correctly, a fence (sidebar) can be "cammed out of engagement with the cylinder shell," and the plug can rotate.

An ordinary pin tumbler lock asks only one question of each pin: is it at the right height? The Medeco design asks two: is it at the right height, and is it turned to the right angle? Both must be true for every pin before the sidebar retracts. A follow-on patent, U.S. 3,722,240 (filed January 25, 1971; granted March 27, 1973; Spain et al.), describes tumblers that "both translate and rotate" to present cavities to a fence.

Product Generations

Medeco's own published timeline (in its Medeco 4 brochure) lists these milestones:

Biaxial. The Biaxial cylinder is covered by U.S. Patent 4,635,455 (filed July 19, 1985; granted January 13, 1987), assigned to Medeco Security Locks. A later Medeco patent (U.S. 6,945,082) gives the background in plain terms. The original design used "skew cut bittings" with "chisel pointed" rotating pins. Biaxial "expanded on the master keying capabilities" by offsetting the bittings along the key blade and giving the pins different offset tips. See master keying.

Medeco3. A Medeco-distributed overview says M3 added a new patented system and "three distinct locking points." Locksmith Ledger notes that M3 uses a slider working with the sidebar.

Medeco 4. Locksmith Ledger reports that M4 launched in January 2021 as the fourth-generation platform. Medeco's catalog says M4 adds side pins and a movable element in the key. All of them must engage the sidebar, together with pins that "lift and rotate." The catalog describes M4 cylinders as UL 437 listed and certified to ANSI/BHMA A156.30 and A156.5. See UL 437 and ANSI/BHMA lock grades.

Patents and Key Control

Medeco's approach to key control rests on utility patents covering both the key and the cylinder. A Medeco overview describes the principle this way: the original patent "protected the Medeco cylinder and the key so no other manufacturer could produce them." Medeco's 2018 release says users are "safeguarded from unauthorized key duplication thanks to utility patents."

Patents expire, so the protection is time-limited. Medeco's 2025 catalog lists the key-control patents for Biaxial (2005) and Medeco3 (2021) as expired and recommends upgrading to M4. It gives M4's patent protection as running to 2040 and X4's to 2030. For the general idea, see restricted keyways.

Key blanks for current platforms are sold at different levels of restriction. The catalog distinguishes, for example, end-user and factory-restricted key programs. Who may order or cut keys is set by the program the owner chooses.

Ownership

Medeco's 2018 anniversary release says the company "was acquired by ASSA ABLOY in Sweden" in 1998 and that Medeco cylinders were still made in Salem, Virginia at that time. It describes Medeco as a division of ASSA ABLOY North America.

Where Medeco Fits

Medeco is one of several high-security cylinder designs that add a second locking principle on top of pin height, such as a sidebar, rotating elements, or sliders. For the wider category and how UL 437 and A156.30 are used to describe it, see high-security locks. No lock is secure on its own. The door, frame, strike plate, and key management all matter.

Related Topics

• High-security locks: the category Medeco helped define
• Sidebar locks: the secondary locking element
• Pin tumbler locks: the base mechanism
• Key control and restricted keyways: patent-based key restriction
• Master keying: what Biaxial expanded
• Interchangeable core: SFIC formats (KeyMark)
• UL 437: the listing Medeco cites
• ABLOY: another high-security cylinder maker

Sources