Protecting national treasures is an open-and-shut case

Sept. 1, 2005
Protecting national treasures is an open-and-shut case

Custom hinges from Weber Knapp make it easier to open and close massive lids on cases protecting the "American Originals" document collection . The collection includes the Gettysburg Address, the voting ledger of the First Constitutional Congress, the Louisiana Purchase agreement, Rosa Parks' arrest records, and President John F. Kennedy's Inaugural Address. The case hinges are part of a renovation that should be completed later this year

The Rotunda of the National Archives Building in Washington, D.C., contains display cases housing the Declaration of Independence, the Constitution, and the Bill of Rights. Flanking these are two sets of seven cases lining the Rotunda's curved walls that display the "American Originals" document collection. Both banks of cases have seven individual glass lids, each framed in ornate bronze castings.

Custom hinges from Weber Knapp counterbalance the massive 140 to 180 lb lids, cutting opening and closing forces to just 10 lb. The hinges are part of a renovation by a National Archives and Records Administration (NARA) team. NARA specs say case lids must stay put (indefinitely) without additional support at any point in their travel. Moreover, no hinge materials can produce emissions that could potentially harm the documents. The hinge assembly must also remain invisible from the case front so as not to detract from the viewing experience. Another challenge: the hinges must follow the curve of the rotunda wall.

The resulting design uses a combined counterbalance/mechanical linkage that fits between the wall and document stands. A special gooseneck arm attaches the hinges to the lid frames. Closed, the lids slope down at 25° and rotate up 60° to their full-open position. The design prompted no major changes to the cases themselves — only a fiber-optic light bar needed a slight redesign to accommodate pivoting motion of the arm. NARA says hinges must last a minimum of 10,000 cycles. Weber Knapp has successfully tested the hinge to 36,500 open/close cycles.

Weber Knapp Co.,
Jamestown, N.Y.,

Sponsored Recommendations

The entire spectrum of drive technology

June 5, 2024
Read exciting stories about all aspects of maxon drive technology in our magazine.


May 15, 2024
Production equipment is expensive and needs to be protected against input abnormalities such as voltage, current, frequency, and phase to stay online and in operation for the ...

Solenoid Valve Mechanics: Understanding Force Balance Equations

May 13, 2024
When evaluating a solenoid valve for a particular application, it is important to ensure that the valve can both remain in state and transition between its de-energized and fully...

Solenoid Valve Basics: What They Are, What They Do, and How They Work

May 13, 2024
A solenoid valve is an electromechanical device used to control the flow of a liquid or gas. It is comprised of two features: a solenoid and a valve. The solenoid is an electric...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!