Electro-Expulsive De-Icing System for Aircraft and Other Applications
An apparatus for removing ice from an object (e.g., in-flight ice removal from the skin of an aircraft) includes an actuator assembly that forms an elongated electrically conductive loop. The actuator is mounted in a position enabling it to impact the object to be de-iced in response to movement of the loop that is produced by electric current pulses flowing in opposite directions in two mechanically independent loop subassemblies. The loop subassemblies include multiple electrically conductive elements interconnected at their ends using elongated flexible connectors in order to introduce a physically discontinuity that reduces any restriction of relative movement of the subassembly ends caused by the connectors, thereby achieving enhanced operation and less fatigue failure as compared to a rigid structure having encapsulated element
This application is a continuation application of U.S. patent application Ser. No. 13/790065 filed Mar. 8, 2013, which application is a continuation of U.S. patent application Ser. No. 12/658304 filed Feb. 5, 2010, now U.S. Pat. No. 9,108,735 issued Aug. 18, 2015, which application claimed the benefit of U.S. Provisional Patent Application Ser. No. 61/216,107 filed May 13, 2009.
BACKGROUND OF THE INVENTION1. Technical Field
This invention relates generally to the field of in-flight aircraft de-icing and the like, and more particularly to an electro-expulsive de-icing system and its component parts for aircraft and other applications.
2. Description of Related Art
An “electro-expulsive de-icing system” is also sometimes referred to as an “electro-mechanical expulsive de-icing system.” It uses electrically produced mechanical motion to knock accumulated ice off a flight surface or other object being de-iced. Recall in that regard that ice removal is an important undertaking because, in the case of aircraft, ice can alter aerodynamic characteristics significantly with catastrophic results. A de-icing system alleviates those concerns.
To accomplish aircraft de-icing, a typical electro-expulsive de-icing system includes electro-mechanical transducers called “actuators” that are installed beneath the skin of various aircraft structures (e.g., the leading edges of wings, horizontal and vertical stabilizers, and engine inlets). In response to in-flight ice formation, an onboard electronic control system passes large current pulses through such actuators (e.g., 8,000-ampere, millisecond duration pulses at 30 to 90-second intervals) in order to thereby produce mechanical motion that produces shock waves in the skin of the aircraft structure. The shock waves result in dislodgement of ice that has accumulated on the skin. The actuator impacts the inner surface of the skin, that action produces the shock waves in the skin, and the shock waves knock the accumulated ice off the outer surface of the skin.
Some such existing electro-expulsive de-icing actuators include strips or ribbons of copper or other electrically conductive material that are mounted beneath the aircraft skin in closely-spaced-apart parallel orientation. Electric current flowing as mentioned above causes the strips to accelerate apart from each other in a manner creating ice-removing shock waves. The electrically conductive strips for some actuators take the form of a copper ribbon wrapped in an elongated multi-turn loop (i.e., a multi-turn coil). A copper ribbon measuring, for example, 0.25 inches to 1.50 inches wide and 0.020 inches to 0.040 inches thick, is wrapped in a multilayer, elongated, loop measuring about one to eight feet in length, with the copper ribbon being wound back on itself at the ends of the loop. Molded blocks of polyurethane encapsulate the two opposite folded ends of the loop while a dielectric coating on the copper ribbon prevents shorting between adjacent turns.
Interconnection of the copper ribbon loop to the onboard electronic control system results in electric current pulses flowing in a first direction in a first half of the loop (from a first folded end of the loop to an opposite second folded end), and in an opposite second direction in a second half of the loop (from the second folded end of the loop to the first folded end). As an electric current pulse flows that way, it results in a large force that tends to mutually repel the first and second halves of the loop. That repulsion results in relative movement of the first and second halves away from each other (e.g., by about 0.08″ to 0.50″) in a pulse of mechanical motion that is coupled to the aircraft skin. That mechanical pulse results in the de-icing shock waves.
Although effective in many respects, some existing actuators of the type described above have certain drawbacks that need to be overcome. First, impact of the skin can be less than desired for adequate ice removal. Actuator operation is sometimes less robust than desired. In addition, the ends of the loop tend to experience fatigue failure. For those and other reasons that will become apparent from the following detailed descriptions, a need exists for a better actuator assembly that overcomes the drawbacks discussed above.
SUMMARY OF THE INVENTIONIn view of the foregoing, it is a primary object of the present invention to provide an electro-expulsive de-icing actuator that alleviates the foregoing concerns. Predicated on a realization that somewhat reduced performance and fatigue failure are a result of the encapsulated loop ends being fixed and unmoveable relative to each other (with essentially a near zero radius at the fold), the present invention achieves the above-stated objective by providing an actuator assembly that includes an electrically conductive loop formed by two mechanically independent loop subassemblies. A first loop subassembly of the two forms a first portion of the electrically conductive loop; current flows in it in a first direction. A second loop subassembly of the two forms a second portion of the electrically conductive loop; current flows in it in an opposite second direction.
The ends of the first and second subassemblies are electrically interconnected by flexible connectors. As a result, the first and second subassemblies (i.e., the first and second portions of the electrically conductive loop) can move apart without the restrictiveness of encapsulated ends. Displacement is less restricted. In addition, the fatigue failure previously experienced at encapsulated ends is avoided. In other words, the inventors of the present invention discovered that mechanical output energy of prior art actuators was being diverted to unproductive deformation and stress in the folded actuator ends and that as a consequence actuator operation was sometimes less robust than desired and the ends of the loop tended to experience the fatigue failure mention previously.
The invention, stated more broadly, provides an apparatus for removing ice from an object, with in-flight ice removal from the skin of an aircraft being one important application. To paraphrase some of the more precise language appearing in the claims and further introduce the nomenclature used, an apparatus constructed according to the invention for impacting an object as part of an electro-expulsive de-icing system includes an assembly referred to as the actuator. The actuator includes multiple electrically conductive elements connected in an electrically conductive loop, and the actuator is mounted on a support structure in a position enabling the loop to impact the object in response to movement of the loop produced by electric current pulses flowing in the loop.
A first subassembly portion of the actuator includes an electrically conductive first element of the loop having two opposite terminal ends referred to as the “first end” and the “second end.” The first element extends between the first end and the second end along a first path, with the first element functioning as means for conducting the electric current pulses in a first direction. A second subassembly portion of the actuator includes an electrically conductive second element of the loop having two opposite terminal ends that are referred to as the “third end” and the “fourth end.” The second element extends between the third end and the fourth end along a second path that is spaced apart from and generally parallel to the first path, with the second element functioning as means for conducting the electric current pulses in a second direction that is generally opposite the first direction.
According to a major aspect of the invention, means are provided for electrically interconnecting the various terminal ends of the first and second elements in order to thereby form the electrically conductive loop. The means for doing so includes at least a first connector that electrically interconnects the second end and the fourth end without preventing movement of the second end relative to the fourth end. The first connector includes an electrically conductive first conductor attached to the second end and the fourth end that is flexible (e.g., a jumper formed from a length of stranded aircraft wire).
Although the foregoing description focuses on just one pair of elements and one connector, an actuator constructed according to the invention preferably includes multiple element pairs and connectors for a multi-turn loop. In other words, the first subassembly preferably includes a first plurality of electrically conductive elements (e.g., three or four) extending in generally parallel relationship to each other. Similarly, the second subassembly includes a second plurality of electrically conductive elements extending in generally parallel relationship to each other. The ends of those elements are interconnected to form the elongated loop using the elongated flexible connectors mentioned above.
Thus, the invention provides an electro-expulsive de-icing actuator that alleviates performance and fatigue failure concerns of the prior art. The enhanced performance offers greater weight savings and design flexibility. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.
With the foregoing comments in mind, next consider
The multiple conductive elements 31A, 31B, 31C, 32A, 32B, and 32C are interconnected by flexible connectors 33, 34, 35, 36, and 37 as illustrated, with the connectors 33-37 in
Unlike the actuator 40 where the axes of elongation of the connectors 43-47 are parallel to the direction of elongation of the electrically conductive loop, the axes of elongation of the connectors 53-55 in
Turning now to
The first subassembly 101 (represented by a broken line at reference numeral 101) includes electrically conductive elements 101A, 101B, and 101C extending along a first path 101 D in the X-Y plane that is perpendicular to the Y axis. The broken line is intended to indicate that the elements 101A, 101B, and 101C are part of the first subassembly 101. Similarly, the second subassembly 102 includes electrically conductive elements 102A, 102B, and 102C extending along a second path 102D in the X-Y plane that is generally parallel to the first path 101D. A current pulse flows in the elements 101A, 101B, and 101C of the first subassembly 101 in a first direction indicated by an arrow 101E as the current pulse flows in the elements 102A, 102B, and 102C of the second subassembly 102 in an opposite second direction indicated by an arrow 102E. That current flow results in the first and second assemblies moving apart for ice-removal purposes as indicated by the arrow 106.
The multi-turn electrically conductive loop (i.e., multi-turn coil) includes the following electrical connector and actuator elements: three connectors 111, 112, and 113 connecting respective ends 116, 117, and 118 of the respective elements 101A, 101B, and 101C to respective ends 119, 120, and 121 of the respective elements 102C, 102B, and 102A; and two opposing connectors 114 and 115 connecting respective opposing ends 122 and 123 of respective elements 101B and 101C to respective opposing ends 124 and 125 of elements 102C and 102B. Wires 128 and 129 connect ends 126 and 127 of the elements 101A and 102A to the control system 105. The connectors provide a physical discontinuity in the multi-turn electrically conductive loop (i.e., a mechanical discontinuity as opposed to an electrical discontinuity) that enhances actuator operation by enabling a designer to specify connectors that are less restrictive to separation of loop subassemblies 101 and 102 than a physically continuous loop configuration and better suited to the precise configuration of the actuator. In other words, the mechanical discontinuity enables connector mechanical properties different than the mechanical properties of the rest of the electrically conductive loop; a designer chooses the connector mechanical properties to be less restrictive and thereby to enhance actuator operation. The connectors 111 through 115 are jumpers in the form of flexible loops as depicted by the connector 130 in
Preferably, the dimension 133 is at least twice the distance that the first and second subassemblies 101 and 102 to which the connector 130 is connected move apart in operation in order that the connector 130 is sufficiently flexible not to restrict such movement significantly. When the actuator to which the connector 130 is connected is in an un-energized state, the connector is in a relaxed state as shown in
Thus, the invention provides an electro-expulsive de-icing actuator that alleviates performance and fatigue failure concerns of the prior art. Although exemplary embodiments have been shown and described, one of ordinary skill in the art may make many changes, modifications, and substitutions without necessarily departing from the spirit and scope of the invention. The system and actuators may be used for ice-removal applications other than in-flight aircraft de-icing. The electro-expulsive de-icing structure (EEDS) can be fabricated in circular configuration for applications such as ship board communication antennas, bridge cabling, and so forth, and in a flat panel configuration for applications such as river way locks or ship board superstructure and so forth. As for the specific terminology used to describe the exemplary embodiments, it is not intended to limit the invention; each specific term is intended to include all technical equivalents that operate in a similar manner to accomplish a similar purpose or function.
Additionally, the connector stress can be reduced by lowering that component of magnetic actuator force generated within the connectors themselves. This deliberate reduction in connector-produced actuation force is accomplished by dispersing the force-generating ampere-turns density and by increasing the length of the distance “d” between mutually opposed current paths as described below (see
In line with the foregoing, it is further desirable for purposes of reducing connector stress that the connectors generate low mechanical actuation force per unit length of conductor than the respective actuator elements to which they are attached. Connectors comprise among other features of their construction, which may be optional or necessary features of their construction, depending on the particular connector, which render them potentially vulnerable to reliability problems if subjected to repetitive mechanical stresses of the type produced by the prior art in which mechanical coupling of actuator movement induces undesirable stress and fatigue into the connectors themselves. Although the invention provides relief from the effects of mechanical coupling between actuator members and connectors, that same electrical current and magnetic force which gives rise to mechanical displacement in the actuator members likewise produces a mechanical force and stress within the connectors themselves.
Typically, for a given number of ampere-turns of current in an actuator, the said mechanical force generated per unit length of connector would be roughly the same as that mechanical force per unit length generated within the actuator, were the connector of same geometry and dimensional displacement between opposing current paths as the actuator itself. In fact, the practical mechanical force generated within the connector may be in fact larger per unit length than that of the actuator, since the connector region constrains the displacement d during actuation through the restriction of conductor movement near the bends within the connector.
With regard to
Fm=I2×N2×μo/d, where:
-
- Fm is the force in Newtons per meter of actuator wire length
- I is the current in the wires in Amperes
- N is the number of paralleled conductors in each leg
- d is the separation distance in meters
- Po is the electromagnetic constant=1.26×10−7
Fm2=I2×1: 4N2×o/d=Fm/4
If two such actuators were widely separated, and driven in an electrically parallel circuit by the original current I evenly shared between the two, we would have one-half of the original current in each such actuator of force Fm/4. If we sum the forces of the two such actuators, we see a resulting force F:
F=2×Fm/4=Fm/2
A similar argument can be made for distributing the ampere-turns of actuator current into more than two separate, that is, N widely spaced conductors, with an even greater corresponding reduction in actuator force. One can thus extrapolate that the force in an actuator is lessened by distributing the current into more conductors, or, in an equivalent manner, constructing the actuator of wide, flat strip instead of in a small circular cross section. More generally, mutually opposed bundles of conductors, each bundle of given cross sectional geometry G and separated by an average displacement d and carrying equal and opposite current densities will exhibit lower actuation force in response to a given actuation current I when the geometry G is large in maximum or average dimension and/or the displacement d is large.
With further regard to the connectors, the invention applies to an electromagnetic actuator having two members mutually opposed and disposed along a path P (e.g., a path extending generally parallel to and midway between the two members shown in
One form of the invention has a type of connectors fabricated and installed in such a way as to extend in a direction substantially divergent from path P so that the connectors relieve the stress of actuator expansion in the direction of force F without drawing the connectors inward along path P. This looks like loops of wire, or like right angle wide flexible strips, per
Claims
1. A de-icing system comprising:
- an object having an outer skin disposed over at least one supporting structure;
- an electroexpulsive actuator comprising: a plurality of sub-assemblies each comprised of at least one electrically conductive element coupled to an electrical input at a first end thereof, at least one electrically conductive flexible connector interconnecting a second end of each of the plurality sub-assemblies, thereby creating a conductive loop from the electrical input of each conductive element to an electrical output thereof, wherein the flexible connectors are configured to allow relative movement along the entire length of each of the sub-assemblies, including the ends thereof, and wherein the sub-assemblies are disposed in an orientation relative to each other such that when electrical current flows through the conductive loop formed thereby a magnetic field is created in the plurality of sub-assemblies and the sub-assemblies are urged apart relative to one another under the influence said magnetic fields; and
- wherein the electroexpulsive actuator is positioned beneath the outer skin of the object such that the relative movement of the subassemblies causes the electroexpulsive actuator to deliver a force to the outer skin of the object that creates a de-icing shockwave therein.
2. The system of claim 1, wherein the electrically conductive elements are in a substantially parallel configuration, and wherein the relative movement is lateral to the longitudinal axis of the conductive elements.
3. The system of claim 1, wherein the connector is one of a plurality of connectors connecting second ends of pairs of electrically conductive elements, each pair comprising an electrically conductive element from the first sub-assembly element from the second sub-assembly and an electrically conductive element from the second sub-assembly.
4. The system of claim 1, wherein the connector is selected from the group consisting of one of either a stranded aircraft wire or a U-shaped loop.
5. The system of claim 1, wherein a longitudinal axis of the connector is one of either parallel to or perpendicular to a longitudinal axis of the conductive elements.
6. The system of claim 1, wherein each of the ends of the sub-assemblies are encapsulated.
7. The system of claim 1, further comprising an inner shell enclosed by the outer skin of the object.
8. The system of claim 7, wherein the actuator is mounted between the inner surface of the outer skin and the outer surface of the inner shell.
9. The system of claim 7, wherein the actuator is mounted to the outer surface of the inner shell.
10. The system of claim 7, wherein the actuator is mounted to the inner surface of the outer skin.
11. The system of claim 7, further comprising an actuator support structure attached to one or both of the inner shell or outer skin.
12. The system of claim 11, wherein the actuator is mounted adjacent to the actuator support structure.
13. The system of claim 12, wherein the actuator support structure comprises a first and second support structure, and the actuator is mounted between the first and second support structure.
14. The system of claim 12, wherein multiple actuators are mounted between the actuator support structure and the inside surface of the skin;
- wherein the first actuator is mounted between one end of the actuator support structure and the inner surface of the skin, the second actuator is mounted between the opposite end of the actuator support structure and the inner surface of the skin.
15. The system of claim 1, wherein multiple actuators are mounted at spatially separated points along the object.
16. A method comprising:
- disposing an electroexpulsive actuator beneath the outer skin of an object in actuating relation thereto, the actuator comprising: a plurality of sub-assemblies each comprised of at least one electrically conductive element coupled to an electrical input at a first end thereof, at least one electrically conductive flexible connector interconnecting a second end of each of the plurality sub-assemblies, thereby creating a conductive loop from the electrical input of each conductive element to an electrical output thereof, wherein the flexible connectors are configured to allow relative movement along the entire length of each of the sub-assemblies, including the ends thereof, and wherein the sub-assemblies are disposed in an orientation relative to each other such that when electrical current flows through the conductive loop formed thereby a magnetic field is created in the plurality of sub-assemblies and the sub-assemblies are urged apart relative to one another under the influence said magnetic fields; and
- inducing an electrical current in the actuator such that current flows through the sub-assemblies thereby creating a magnetic field in the plurality of sub-assemblies thereby creating a relative movement of the subassemblies, said relative movement being sufficient to deliver a force to the outer skin of the object thereby creating a de-icing shockwave therein.
17. The method of claim 16, wherein the actuator is mounted between the inner surface of the outer skin and the outer surface of the inner shell.
18. The method of claim 16, wherein the actuator is mounted to the outer surface of the inner shell.
19. The method of claim 16, wherein the actuator is mounted to the inner surface of the outer skin.
20. The method of claim 16, further comprising an actuator support structure attached to one or both of the inner shell or outer skin.
21. The method of claim 20, wherein the actuator is mounted adjacent to the actuator support structure.
22. The method of claim 21, wherein the actuator support structure comprises a first and second support structure, and the actuator is mounted between the first and second support structure.
23. The method of claim 21, wherein multiple actuators are mounted between the actuator support structure and the inside surface of the skin;
- wherein the first actuator is mounted between one end of the actuator support structure and the inner surface of the skin, the second actuator is mounted between the opposite end of the actuator support structure and the inner surface of the skin.
Type: Application
Filed: Mar 9, 2016
Publication Date: Jun 30, 2016
Inventors: Richard Alexander Olson (Fallbrook, CA), Mark Ronald Bridgeford (Alta Loma, CA)
Application Number: 15/064,957