Bi-stable microswitch including shape memory alloy latch

Details Bi-stable microswitch including shape memory alloy latch Bi-stable microswitch including shape memory alloy latch

2001-06-21

2003-08-05

Gandhi, Jayprakash N. (Department: 2125)

Electricity: electrothermally or thermally actuated switches

Thermally actuated switches

With fusible, combustible or explosive material

C337S131000, C337S141000, C337S140000

Reexamination Certificate

active

06603386

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to microswitch arrays and microswitch array elements for switching electrical signal lines. The invention is applicable to the switching of telecommunications signal lines and it will be convenient to hereinafter describe the invention in relation to that exemplary, non limiting application.
Switching arrays are used in telecommunication applications, when a large number of telecommunication signal lines are required to be switched. Generally, such switching arrays are provided by the permanent connection of copper pairs to “posts” or underground boxes, requiring a technician to travel to the site of the box to change a connection.
In order to remotely alter the copper pair connections at the box without the need for a technician to travel to the site, there have been proposed switching arrays consisting of individual electro mechanical relays wired to printed circuit boards. However, this type of array is complex, requires the addition of various control modules and occupies a considerable amount of space. Further, current must be continuously provided through the relay coil in order to maintain the state of the relay. Since in many applications switching arrays elements are only rarely required to be switched, this results in an undesired power consumption.
It would therefore be desirable to provide a switching array and switching array element which ameliorates or overcomes one or more of the problems of known switching arrays.
It would also be desirable to provide a bi-stable broad band electrically transparent switching array and switching array element adapted to meet the needs of modem telecommunications signal switching.
It would also be desirable to provide a switching array and switching array element that facilitates the remotely controllable, low power bi-stable switching of telecommunication signal lines.
SUMMARY OF THE INVENTION
With this in mind, one aspect of the present invention provides a bi-stable microswitch including a pair of contacts and an armature movable between a first position and a second position to selectively make or break the pair of contacts, the armature being latched in the second position by a shape memory alloy latch, wherein the shape memory alloy latch is caused to deform upon heating so as to permit the armature to return to the first position.
In one embodiment, the armature includes a shape memory alloy element causing movement of the armature from the first position to the second position upon heating of the armature.
The armature may be resiliently biased towards the first position when latched so that upon removal of the heat and the deformation of the shape memory alloy latch, the armature returns to the first position.
The bi-stable microswitch may further include a first heating device formed on or proximate the shape memory alloy latch. A second heating device may also be formed on or proximate the armature. One or more of the first and second heating devices may include an electrical resistance element.
Alternatively, heat may be applied to at least one of the armature and the shape memory alloy latch by means of electromagnetic radiation. For example, laser, microwave or other radiation may be applied by non-contact means from a remote location.
Another aspect of the invention provides an array of bi-stable microswitches as described above. Each of the microswitches may be at least partly formed in a common substrate by micromachining techniques.


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