Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
1999-09-27
2001-10-30
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C361S726000, C070S163000, C070S277000, C337S140000
Reexamination Certificate
active
06310411
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to locks and, more particularly, to an electrically controlled lock suitable for use in locking personal computer cases.
BACKGROUND OF THE INVENTION
It is highly desirable to secure the cover of a personal computer in order to protect information stored in the computer and to prevent unauthorised access to or removal of the components within the case.
One known lock system used for instance in the HP Vectra series of computers is a mechanism similar to a conventional key operated lock, actuated by a key in the rear of the machine. Two people are enabled to unlock the cover: the key owner and the system manager. The system manager can open all machines that he is in charge of using a programmable master key. Other examples of key operated locks can be found described in U.S. Pat. No. 5,548,981 and U.S. Pat. No. 5,598,323.
One of the main advantages of using key operated locks is that the cover can be removed even if there is no power on. However, if a technician is required to open the computer to repair or replace a component, then that person must be physically in possession of one of the keys. It is not with this system possible to provide for software control of the lock to enable desirable functionality such as remote locking and unlocking of the cover or password controlled access.
Such features are particularly desirable for customers that own and manage very many PCs, and therefore that need to manage access to hardware more easily. If hardware changes are desired in many machines at the same time, the system manager can access systems without having to locate keys and can unlock machines over a computer network, using appropriate hardware management software tools like ones included in the HP Toptools package, available from Hewlett-Packard Company.
In order to allow remote locking and unlocking of computer covers, electronically controlled cover lock mechanisms have been used. For example the Compaq Deskpro 4000 and 6000 models employ an electromechanical lock that use a bistable solenoid.
A bistable lock is needed because safety specifications require the machine to be switched off for the removal of the cover. In consequence, the unlocked position of the soft lock has to be mechanically stable. Since the need for security requires that the lock prevent the removal of the cover even if the machine is not supplied with power, the lock position has also to be mechanically stable.
A suitable bistable solenoid for use in such locks is the MSA model L-09432 that is available from MAGNET-SCHULTZ OF AMERICA. This solenoid is electronically connected to the computer motherboard by 3 wires (−12V, 0, 12V). The locking and unlocking operation is performed by powering the solenoid during one second.
Whilst this solution is generally satisfactory, it is relatively expensive and does present certain drawbacks. For instance, use of a solenoid creates a certain amount of electromagnetic radiation. Since the electromagnetic emissions from computers are subject to strict controls, extra shielding or special design of the case may be required to reduce the radiation coming from the solenoid. In addition, the solenoid coil itself is inevitably somewhat bulky and adds to the weight of the computer.
This invention is directed to mitigating the drawbacks of the prior art.
SUMMARY OF THE INVENTION
In brief, this is achieved by a lock assembly for a personal computer comprising a lock member movable between a locked position and an unlocked position and a shape memory wire arranged to move the lock member between the lock position and the unlocked position in response to one or more electrical signals that generate currents therein.
In a preferred embodiment, the lock assembly is provided with a bistable mechanical biasing arrangement for biasing the lock member into the locked position or the unlocked position. Suitably, the mechanical biasing arrangement can be a leaf spring.
In one implementation, the shape memory wire includes a first portion forming a first current path for pulling the lock member into the lock position and a second portion forming a second current path for pulling the lock member into the unlocked position.
For convenience, one end of the first current path and one end of the second current path can be connected to a common terminal, the first and second current paths each comprising respective terminals at ends remote from the common terminal. In this arrangement, a lock signal is represented by a voltage applied between the terminal at the end of the first current path and the common terminal and an unlock signal is represented by a voltage applied between the terminal at the end of the second current path and the common terminal.
Also provided is a computer comprising a housing having a first section having a wall defining an opening for allowing access to internal components of the computer; a cover section for engaging the first section to close the housing; and a lock assembly as described arranged to prevent or allow disengagement of the first section and the cover.
This arrangement has the advantages of the solenoid-based solution described above but can be implemented at reduced cost. In addition EM emissions and the weight and bulk of the device are reduced. Whilst the shape memory wire is in some ways less robust than the solenoid solution, the invention is based in part on the recognition that in this application the actual number of cycles that the lock needs to tolerate is relatively low—the number of times that the case needs to be opened is perhaps as low as only 100 over the life of the machine. Commercially available shape memory alloy wires are easily capable of surviving this number of duty cycles.
REFERENCES:
patent: 5548981 (1996-08-01), Kirk
patent: 5598323 (1997-01-01), Muller
patent: 5769159 (1998-06-01), Yun
patent: 5905446 (1999-05-01), Benore et al.
patent: 5977858 (1999-11-01), Morgen et al.
patent: 5990777 (1999-11-01), Whiteman, Jr.
patent: 6008992 (1999-12-01), Kawakami
patent: 6082153 (2000-07-01), Schoell et al.
patent: 6240727 (2001-06-01), Goldstein et al.
Ballato Josie
Hewlett--Packard Company
Roberto Rios
LandOfFree
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