1. Field
The disclosed and claimed concept relates generally to electrical interruption equipment and, more particularly, to a circuit interruption device that employs a shape memory alloy element.
2. Related Art
Circuit interruption devices of many types are well understood in the relevant art. Among such well-known circuit interruption devices are circuit breakers, vacuum interrupters, ON/OFF switches, and the like without limitation. While circuit interruption devices have been generally effective for their intended purposes, they have not been without limitation.
Some applications require a circuit interruption device that is capable of operating in a high current environment, such as where current on the order of 400-500 Amperes is continuously fed. A circuit interruption device suited to such a circuit may potentially be difficult to move between ON and OFF positions. For this reason and for other reasons, such circuit interruption devices have thus sometimes employed devices such as solenoids and other such devices to switch the circuit interruption device to its OFF position in certain predefined circumstances. It is furthermore noted, however, that a solenoid that is suited to open the contacts of a circuit interruption device rated for 400-50 Amperes continuous feed can be bulky and heavy. Such bulk and weight are undesirable in certain applications, such as aerospace applications. It thus would be desired to provide an improved circuit interruption device.
According to one aspect, a circuit interruption device includes a support, a set of separable contacts being movable between an OPEN condition and a CLOSED condition, and a first member situated on the support and being movable between an OFF position that corresponds with the OPEN condition and an ON position that corresponds with the CLOSED condition. The movable member is biased toward the first position and has a first surface and a second surface. The circuit interruption device also includes a second member situated on the support and that is movable between an extended position and a retracted position. The second member is biased toward the extended position and has another first surface and another second surface. The circuit interruption device also includes a transport mechanism which includes a shape memory alloy element that is transformable between a first shape and a different second shape responsive to an electrical pulse. In a first configuration of the circuit interruption device, the first member is in the OFF position, the second member is in the extended position, the shape memory alloy element is in its first shape, and the first surface and the another first surface are engaged with one another and are structured to resist movement of the first member away from the OFF position. Responsive to an electrical pulse, the shape memory alloy element is structured to transform into its second shape and to move the first member toward its ON position. In a second configuration of the circuit interruption device, the second member is in the extended position, and the another second surface is engageable with the second surface to resist movement of the first member away from the ON position.
A further understanding of the disclosed and claimed concept can be gained from the following Description when read in conjunction with the accompanying drawings in which:
Similar numerals refer to similar parts throughout the specification.
An improved circuit interruption device 4 is depicted generally in
The circuit interruption device 4 can be generally said to include a support 12 upon which are disposed an operation apparatus 16 and a latch apparatus 20. The operation apparatus 16 can be said to include an operating member 24 that is translatable along a first longitudinal direction 28 between an ON position that is depicted generally in
The operation apparatus 16 can further be said to include a return spring 32 that biases the operating member 24 toward the OFF position and to further include a transport mechanism 36. As will be set forth in greater detail below, the transport mechanism 36 is operable to move the operating member 24 from the OFF position to the ON position responsive to an electrical pulse.
The operating member 24 can itself be said to include an elongated rod 40 that is operatively connected with a movable contact of the set of separable contacts 6 as is depicted generally in
The transport mechanism 36 can be stated to include a shape memory alloy element 56 and a heat sink 60, with the shape memory alloy element 56 having a connection 64 with the operating member 24, and with the shape memory alloy element 56 having another connection 68 with the heat sink 60. In the depicted exemplary embodiment, the shape memory alloy element 56 extends about a portion of a perimeter of a pin 72 that is mounted on the support 12. The heat sink 60 is itself mounted on the support 12 in the depicted exemplary embodiment.
The shape memory alloy element 56 is formed of a Single Crystal Shape Memory Alloy (SCSMA) that can be formed from a metallic alloy whose constituents may largely include copper-aluminum-nickel (Cu—Al—Ni) or other appropriate alloy. An SCSMA has various advantages over a conventional Shape Memory Alloy (SMA), and thus the shape memory alloy element 56 is desirably formed of an SCSMA. Advantages of an SCSMA include significantly greater strain recovery, 9% versus 3% for an SMA. Further advantages of an SCSMA over an SMA include true constant three deflection, and very narrow loading hysteresis and recovery which are generally 100% repeatable and complete. An SCSMA additionally has a transition temperature range that may be, for instance, in the range of −200° C. to +250° C., which is a greater transition range than a conventional SMA. Other advantages are known in the general art. It is also noted, however, that the shape memory alloy element 56 may be formed from an SMA depending upon the needs of the particular application.
As is generally understood in the art, a shape memory alloy material such as a conventional SMA or an improved SCSMA is typically formed to have some type of an original shape. The SMA or the SCSMA can thereafter be deformed by bending, stretching, and the like into any of a variety of shapes while it remains at a temperature that is less than its transition temperature. Upon heating the SMA or the SCSMA to its transition temperature, however, the shape memory alloy transforms from its deformed shape back into to its original shape. Upon cooling of the shape memory alloy below its transition temperature, it may return to the deformed shape.
Accordingly, the shape memory alloy element 56 employed herein is movable between an original shape and a deformed shape. The shape memory alloy element 56 returns to its original shape in response to heating, which is provided by an electrical pulse applied to the shape memory alloy element 56. More particularly, the shape memory alloy element 56 is, in the depicted exemplary embodiment, an elongated structure whose length changes when it moves between the deformed shape and the original shape. The original shape is of an elongated configuration and is of a relatively shorter length whereas the deformed shape is likewise of an elongated configuration but of a relatively longer length. When an electrical pulse is applied to the shape memory alloy element 56 and heats it above its transition temperature, the shape memory alloy element 56 shortens from its relatively longer deformed shape to its relatively shorter original shape. As will be set forth in greater detail below, such shrinking or reduction in the length of the shape memory alloy element 56 that is occasioned by the electrical pulse applied thereto causes the operating member 24 to be moved from its OFF position to its ON position.
In the depicted exemplary embodiment, the shape memory alloy element 56 is an elongated fiber formed of an SCSMA. When the shape memory alloy element 56 is heated by the aforementioned electrical pulse applied thereto, the length of the shape memory alloy element 56 shrinks by approximately 9%, which is a change in length that is sufficient to move the operating member 24 from its OFF position to its ON position, which will be described in greater detail below.
The exemplary heat sink 60 is formed from aluminum or other appropriate thermally conductive material and is configured to rapidly cool the shape memory alloy element 56 to a temperature below its transition temperature subsequent to the application of the electrical pulse. The heat sink 60 does so in a generally understood fashion by shunting heat away from the shape memory alloy element 56. The heat sink 60 is desirably configured to have a heat shunting capacity that is great enough to provide sufficient heat shunting to cool the shape memory alloy element 56 to a temperature below its transition temperature despite repeated operation of the circuit interruption device 4. That is, the heat sink 60 has a sufficient heat shunting capacity that it will continue to cool the shape memory alloy element 56 below its transition temperature in an environment of repeated applications of electrical pulses to the shape memory alloy element 56 and dissipation of the heat generated therefrom to the heat sink 60.
The latch apparatus 20 can be generally said to include a solenoid 76 and a biasing element 80 that are both situated on the support 12. The solenoid 76 is a miniature solenoid and includes an electrical coil 84 such as a close coil and plunger 88. The plunger 88 is movable along a second longitudinal direction 90 between an extended position as is depicted generally in
The plunger 88 can be said to include a latching element 92 at an end thereof that interacts with the flange 44 of the operating member 24. The latching element 92 includes an angled surface 94 and an engagement surface 98 that face generally away from one another. In the depicted exemplary embodiment, the angled surface 94 is oriented oblique to both the second longitudinal direction 90 and the first longitudinal direction 28. Further in the depicted exemplary embodiment, the exemplary engagement surface 98 is oriented substantially perpendicular to the first longitudinal direction 28 and generally parallel with the second longitudinal direction 90. It can be seen that the abutment surface 52 is likewise oriented.
The circuit interruption device 4 in
More particularly, and as can be generally understood from
When it is desired to switch the circuit interruption device 4 from its OFF position to it ON position, an electrical pulse is applied to the shape memory alloy element 56 which, as set forth above, heats the shape memory alloy element 56 and causes it to transform from its relatively longer deformed shape to its relatively shorter original shape. Such shrinking or contraction or shape transformation by the shape memory alloy element 56, i.e., changing its length from the relatively longer length of the deformed shape to the relatively shorter length of the original shape, causes a tensile force to be applied to the operating member 24. Such tensile force is applied to the operating member 24 in the first longitudinal direction 28 and generally in the upward direction from the perspective of
As mentioned above, the length of the shape memory alloy element 56 shrinks by approximately 9% when the shape memory alloy element 56 is heated by the electrical pulse. In the depicted exemplary embodiment, the set of separable contacts 6 have a nominal arc gap of 0.038 inches in the OPEN condition. Moreover, the movable portion of the set of separable contacts 6 is additionally movable with respect to the operating member 24 along the first longitudinal direction 28 to provide for an over-travel and/or wear allowance. As such, the total exemplary movement of the operating member 24 along the first longitudinal direction 28 between the ON and OFF positions is 0.053 inches. Therefore, using wire that contacts 9% would require 0.589 inches of wire length to achieve the desired total movement. In the depicted exemplary embodiment, the wire that forms the shape memory alloy element 56 is of a diameter on the order of 0.020 inches. Multiple wires twined together can be used to increase force with the same total movement.
Once the tensile force applied by the shape memory alloy element 56 to the operating member 24 moves the plunger 88 sufficiently toward the retracted position that the ramped and angled surfaces 48 and 94 are no longer engaged with one another, i.e., they are disengaged, the contraction of the shape memory alloy element 56 and the resultant tensile force applied to the operating member 24 cause the operating member 24 to be translated along the first longitudinal direction 28 in the upward direction from the perspective of
It is particularly noted that
It thus can be understood that the electrical pulse which is applied to the shape memory alloy element 56 causes the shape memory alloy element 56 to transition from its deformed shape to its original shape and to thereby move the operating member 24 and the circuit interruption device 4 to the ON position. In such a position, the interaction between the flange 44 and the latching element 92 and, more particularly, the interaction between the abutment surface 52 and the engagement surface 98, assist in retaining the circuit interruption 4 in its ON position. This can be said to be a second configuration of the circuit interruption device 4. Advantageously, since the solenoid 76 is in its de-energized condition when the circuit interruption device 4 is in its ON position as is depicted generally in
When it is desired to move the circuit interruption device 4 from its ON position that is depicted generally in
It is understood that
It thus can be seen that the circuit interruption device 4 is movable from its OFF position to its ON position as a result of an electrical pulse applied to the shape memory alloy element 56. After application of such an electrical pulse to the shape memory alloy element 56, the latching element 92 and the flange 44 cooperate with one another to retain the operating member 24 and thus the circuit interruption device 4 in the ON position while the coil 84 of the solenoid 76 is in a no-load state. The circuit interruption device 4 in its ON position can then be returned to its OFF position by electrically pulsing or energizing the coil 84 of the solenoid 76, which causes the latching element 92 and the flange 44 to be removed from interaction with one another sufficiently that the return spring 32 can move the operating member 24 and thus the circuit interruption device 4 to the OFF position. Moreover, and as set forth above, when the coil 84 of the solenoid 76 is then de-energized, the biasing element 80 returns the latching element 92 into engagement with the flange 44 whereby such structures retain the circuit interruption device 4 in its OFF position, with the solenoid 76 again being in a no-load state. In such a position, the shape memory alloy element 56 is likewise in a no-load state.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the an that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
Number | Date | Country | |
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61944654 | Feb 2014 | US |