Shape memory alloy locking mechanism

#The present invention generally relates to high-availability computers and servers, and more specifically to a small form factor latch utilizing shape memory alloy (SMA) actuators to implement computer-controlled retention of serviceable components.

#The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. To be sure, today's computers are more sophisticated than early systems such as the EDVAC. Fundamentally speaking, however, the most basic requirements levied upon computer systems have not changed. Now, as in the past, a computer system's job is to access, manipulate, and store information. This fact is true regardless of the type or vintage of computer system.

#High-availability (HA) computers are the result of a system design approach focused on maximizing system readiness, or conversely, on minimizing unplanned downtime. The key tools used by designers of these systems are redundancy and spare capacity. To facilitate redundancy and capacity, HA systems frequently utilize arrays of direct access storage devices (DASD), such as hard disk drives, organized and used in a redundant fashion. This allows each DASD device to be replaced without losing stored data. These arrays may often be combined with hot-swapping technology, which provides the ability to remove and replace hardware without interrupting the operation of the system/server. In this way, DASD's can be replaced without requiring the HA computer to be shutdown.

#So that the manner in which the above recited aspects are attained and can be understood in detail, a more particular description of embodiments of the invention, briefly summarized above, may be had by reference to the appended drawings.

#It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

#FIG. 1 illustrates one embodiment of a shape-memory-alloy (SMA) computer-controlled locking and unlocking mechanism.

#FIG. 1 illustrates one embodiment of a computer-controlled locking mechanism 100. This embodiment 100 includes a frame 110, an actuator arm 120, a clockwise biasing wire connector 142a, and a counterclockwise wire connector 142b. The actuator arm 120, in turn, comprises a pivot pin 124, a locking pin 122 integrated into one end 127, an over-center mechanism 126 integrated into the opposite end 128, two guide posts 129a and 129b, and two stop blocks 190a-190b. The locking pin 122 and a center point 133 of the over-center mechanism 126 are axially aligned with the pivot pin 124 along a long axis 131 of the actuator arm 120. The guide posts 129a and 129b, in turn, are offset from the long axis 131 by lever arms 132a and 132b. The frame 110 in this embodiment includes two locking yokes 160a and 160b that hold the actuator arm 120 against the frame 110 and provide an opposing surface against which the stop blocks 190a-190b can be biased, a pivot guide hole 220 (FIG. 2), and two guide shoulders 180a and 180b. The locking yokes 160a and 160b and the guide posts 129a and 129b cooperate to allow the actuator arm 120 to pivot around the pivot pin 124 between a locked position and an unlocked position. Each guide shoulder 180a and 180b contains four guide slots 146a-146h, two on the upper surface of the shoulders 180a and 180b and two on the lower surface of the shoulders 180a and 180b.

#The embodiment 100 further includes two sets of two shape-memory-alloy (SMA) biasing wires 130a-130d, for a total of four wires. Each SMA wire 130a-130d is held inside one of the wire connectors 142a and 142b by the shoulders 180a and 180b, strung through the integrated wire guide slots 146a-146h, and looped around the guide posts 129a and 129b. One set of SMA wires 130a-130b will pivot the actuator arm 120 in a clockwise direction around the pivot pin 124 when heated, while the other set of SMA wires 130c-130d will pivot the actuator arm 120 in a counter-clockwise direction around the pivot pin 124 when heated.

#The wire connectors 142a and 142b in this embodiment slide into and along guide members 210-211 (FIG. 2) in the frame 110 and are held in place by an integrated flexible latch 141. Each wire connectors includes four vias 144 that individually and electrically connect one of four signal wires 150 to an end 430 (FIG. 4) of one of the SMA wires 130a-130d. A control connector 170, in turn, couples the signal wires 150 to DASD locking controller (not shown). The wire connectors 142a and 142b also securely fix the ends 430 of the SMA wires 130a-130d, thereby providing a point against which the SMA wires 130a-130d can pull when toggling the locking mechanism 100 between its locked and unlocked positions. In some embodiments, the guide members 210-211 and the flexible latches 141 may be further offset from the long axis 131 than are the guide posts 129a and 129b to provide additional actuation force.