Electrically coded piezoelectric lock mechanisms are strong, have few moving parts, are resettable, and are relatively unaffected by high magnetic fields. Codes are extremely difficult to circumvent

Stuetzer, O. M.

English

NASA Technical Reports Server

August 1969
	
Brief 69-10281 
•
ICY C
	
AEC-NASA TECH BRIEF 
4Tf$ O 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Piezoelectric Lock Mechanism Resists Lockpicking 
Most lock mechanisms which operate by response 
to electrical codes can be circumvented if a voltage is 
applied or a circuit is closed at the proper point. Fur-
thermore, electrical memory circuits used in the coding 
operations are generally sensitive to high magnetic 
fields which may destroy the memory. Electrical codes 
may be deciphered with sufficiently sophisticated 
techniques, or the circuitry may be damaged by the 
application of undesirable electrical impulses. 
Electrically coded piezoelectric lock mechanisms 
that have been developed are free of these pfoblems. 
Their codes are extremely difficult to circumvent be-
cause the operator must know in which polarity to 
apply power from an external source to each of the 
piezoelectric elements. (For 10 active elements, the 
number of possible combinations is almost 1,000,000.) 
The lock mechanisms are rugged, have few moving 
parts, are resettable, and are relatively unaffected by 
high magnetic fields. Random trial-and-error attempts 
to open a piezoelectric lock make its operation progres-
sively more difficult. 
Piezoelectric materials, especially ferroelectric and 
anti ferroelectric ceramics, are subjected to high-
mechanical stresses under electrical fields. The as-
sociated dimensional changes (strains), while quite 
small, permit the blocking or release of tightly fitting 
pieces of the strain elements made of these materials. 
These characteristics provide the basis for the con-
struction of simple, electrically controlled lock mecha-
nisms which incorporate either ferroelectric or anti-
ferroelectric locking elements. 
Ferroelectric locking elements have a built-in 
memory. The electrical release code can be varied by
changing their polarization. Locks with antiferroelec-
tric elements are easier to build than those with ferro-
electric elements and require a minimum of machining 
accuracy, but they have no memory. To effect a com-
bination change in an antiferroelectric lock requires 
either mechanical disassembly or a change of the 
wiring. The strains obtainable with the antiferroelec-
tric locking elements are much greater than those with 
ferroelectric elements. 
Notes: 
I. Detailed descriptions of these locks are given in 
U.S. Patent No. 3,390,559, available for 50 cents 
from the Commissioner of Patents, Washington, 
D.C. 20231. 
2. Inquiries concerning this invention may be directed 
to:
Sandia Office of Industrial Cooperation 
Org. 3416 
Sandia Laboratories 
Albuquerque, New Mexico 87115 
Reference: B69-10281 
Patent status: 
Inquiries about obtaining rights for commercial use 
of this invention may be made to: 
Mr. Dudley W. King, Chief 
Albuquerque Patent Group 
U.S. Atomic Energy Commission 
Albuquerque Operations Office 
P. 0. Box 5400 
Albuquerque, New Mexico 87115 
Source: 0 M. Stuetzer 
(SAN-10037) 
Category 01 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
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Piezoelectric lock mechanism resists lockpicking

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