|Publication number||US20070164015 A1|
|Application number||US 11/687,255|
|Publication date||Jul 19, 2007|
|Filing date||Mar 16, 2007|
|Priority date||Mar 14, 2005|
|Also published as||CA2572785A1, CA2572785C, EP1809073A1, EP1809073B1, US7211772, US20060201933|
|Publication number||11687255, 687255, US 2007/0164015 A1, US 2007/164015 A1, US 20070164015 A1, US 20070164015A1, US 2007164015 A1, US 2007164015A1, US-A1-20070164015, US-A1-2007164015, US2007/0164015A1, US2007/164015A1, US20070164015 A1, US20070164015A1, US2007164015 A1, US2007164015A1|
|Inventors||Richard Carpino, James Mullen|
|Original Assignee||Goodrich Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (4), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a Continuation of U.S. patent application Ser. No. 11/331,003 filed Jan. 13, 2006, now U.S. Pat. No. ______, which is a Continuation-in-part of U.S. patent application Ser. No. 11/078,707, filed Mar. 14, 2005, pending, whose contents are incorporated by reference in their entirety.
Heaters are used in many applications where heat is required to help warm an adjacent area. Electrothermal heating is a common way to warm surfaces and spaces on an aircraft by providing heaters bonded to or integrated within the structure. It may also be used in internal areas of an aircraft, examples in areas such as the cockpit cabin or floors for warning, pipes that may contain liquids that could freeze, and even for volumetric heating of a passenger or air cargo compartment. In electrothermal heating systems, heat energy is typically applied through a metallic heating element via electrical power supplied by aircraft or appropriate application generators. Typical heating elements are made from foil, wire and metallic-coated fabrics.
Generally, the heating element of an electrothermal heater should be highly flexible to conform to many types of surface areas and shapes to be protected. Such surface areas may be either two- or three-dimensional. In addition, such heating elements should also withstand fatigue and foreign object damage (FOD) requirements for each particular application. Further, such heating elements should be capable of being specifically designed to provide exact power levels (heat) and uniform heat distribution to the warmed surfaces or regions.
Most current heater elements are made from a single channel foil or wire element assembly 100, 200, respectively, as exemplified by the illustrations of
In one aspect, the present invention is directed to a foil heating element. The foil heating element in accordance with the present invention comprises a patterned foil sheet. The patterned foil sheet includes a first discrete region patterned with a first plurality of holes forming multiple conductive ribbons and having a first sheet resistivity, and it also includes a second discrete region patterned with a second plurality of holes forming multiple conductive ribbons and having a second sheet resistivity. At least some of the multiple conductive ribbons in the first discrete region are in electrical continuity with at least some of the multiple conductive ribbons in the second discrete region.
The differences in sheet resistivity may be the result of using different hole sizes, different hole shapes and varying the hole center spacings in each region, or combinations of these, in the patterned foil sheet. Also, the first discrete region, the second discrete region and a third discrete region, each having a different sheet resistivity may all adjoin a first junction strip of the foil heating element
In another aspect, the present invention is directed to an electrothermal heating assembly comprising such a foil heating element sandwiched between first and second layers of material. The electrothermal heating assembly may comprises two or more such heating elements, and these may lie in the same plane. Also, the first and second layers of material may be both thermally conductive and electrically insulative.
The foil sheet is patterned with a plurality of holes. The patterning can be realized in a number of ways, such as perforating, stamping, etching or by employing other techniques to form holes in such a foil sheet.
In one embodiment etching is employed to form the pattern of holes. Typically, the sheet is initially etched using a patterned mask to form a pattern of openings and then a surface etch of the entire surface is performed to uniformly reduce the sheet thickness. During this surface etch, the sheet's resistance is monitored until a desired value is reached. The resulting sheet is then placed in a laminate comprising electrically insulative, but thermally conductive layers. In one embodiment the etched sheets are sandwiched between a layers of KAPTON® polyimide film, preferably between 1-5 mils thick. In another embodiment the layers may be formed of fiberglass. In still other embodiments, epoxy or neoprene/urethane layers may be used. Other techniques and parameters for manufacturing and laminating such a heating element are known to those skilled in the art.
The heating element 300 seen in
The patterned region 306 comprises a plurality of holes 308 separated by ribbons 310. As best seen in
The patterned region 306 has a length L defined by opposite first and second ends 312, 314, respectively. A first direction, indicated by the arrow A, is defined from the first end 312 to the second end 314. The arrow A depicts the overall direction of current flow in the heating element 300. As seen in
In the embodiment of
The holes 308 in the first patterned region 104 results in the creation of multiple electrical paths between the first end 312 and the second end 314. Furthermore, the holes 308 are arranged in a direction transverse to the first direction A such that the first patterned region 306 is devoid of a continuous section of foil material between the first end 312 and the second end 314 along a line parallel to said first direction A. In other words, when viewed along the first direction A, there is no straight-line path of foil material in areas away from the lateral edges 316, 318. This is because the holes 308 are configured and dimensioned such that the multiple electrical paths in areas away from lateral edges of said first patterned region are all non-parallel to said first direction—the paths being forced to travel around the holes.
In the embodiment of
As seen in
In general, it is understood that varying hole sizes, hole shapes and hole center spacings all influence the sheet resistivity by affecting the ribbon widths (and thus the ribbon cross-sectional area), the path lengths of each ribbon element, and the number of such paths, respectively. Such actions can change the metal volume of a given cross section of the heating element, thereby changing sheet resistivity.
The metal/hole patterns of the heating element embodiments described thus far generate a robustness through their redundant circuitry. They have more ribbons (metal channels) than a typical current heaters seen in
In one embodiment, the junction strip is approximately 12.5 cm wide and has a maximum height of about 1.8 cm at is center, above the gap 730. The buses 706A, 706B are about 6.0 cm wide and the gap 730 has a width of about 0.5 cm. It is understood that these values are only exemplary and that other values for these parameters may be equally suitable.
The lower portions of the buses 706A, 706B are not shown in
The left bus 706A and the right bus 706B each comprise regions with diamond-shaped holes of the sort seen in the embodiment of
Ideally, during use, the heating element 700 has a certain output power or heating performance requirement. As a consequence, the heating element 700 generally must maintain a uniform target surface temperature within some tolerance. In the general case, this can be given by X±Y, where X is the target surface temperature and Y is a tolerance, both values being given in degrees. As an example, the target surface temperature may be 130° F.±5° F. When the heating element does not meet the target temperature, cold spots may form in first regions 722, 724 while hot spots may form in second regions 726 between the first regions. In the exemplary embodiment of
Importantly, in heating element 800, the first bus 806A comprises two patterned regions marked 850A, 860A. In the embodiment of
This difference in sheet resistances is the result of each patterned region 850A, 860A having a different ribbon-to-gap ratio, which is a ratio of the area of the ribbons that remain to the surface area of the holes formed. In particular, the ribbon-to-gap ratio in the first region 850A is larger than the ribbon-to-gap ratio in the second patterned region 860A. This difference in ribbon-to-gap ratios can be correlated to differences in average ribbon widths between the holes in the two patterned regions. It should be evident to one skilled in the art that a smaller average ribbon width translates into a smaller ribbon cross-sectional area, and thus, larger sheet resistance.
By way of example, in the embodiment of
In the embodiment exemplified by heating element 800, the centers of all the holes 855A, 865A, regardless of the region 850A, 860A to which they belong, are evenly spaced apart. The difference in ribbon-to-gap ratios results from forming holes 855A of one size in the first region 850A and holes 865A of a second, larger size in the second region 860A. It is understood that differences in sheet resistance in each region can be achieved by one or more of using different hole sizes, different hole shapes and varying the hole center spacings in each region 850A, 860A, and combinations thereof.
In the embodiment of
Also, in the embodiment of
The second bus 806B is similar in construction to the first bus 806A, having first lateral edge 816B and second lateral edge 818B. Second bus 806B also comprises first patterned region 850B separated from second patterned region 860B by boundary 870B. In the embodiment of
The heating element 800 is made by etching a foil sheet of the type described above using a specially designed mask having at least two different regions, each with different hole sizes. People skilled in the art know how to make such masks, once the pattern is understood.
Heating element 990 comprises first junction strip 902, second junction strip 904, third junction strip 906, first bus 930 and second bus 940. A first electrical contact 980 in communication with the first junction strip 902 provides a first terminal for connecting to a power supply.
The first bus 930 comprises a first patterned region 932 which adjoins both the first junction strip 902 and the second junction strip 904. The first bus 930 also comprises a second patterned region 934 that adjoins the first junction strip 902 and a third patterned region 936 that adjoins the second junction strip 904. As seen in
The sheet resistivities of the second and third patterned regions 934, 936 both differ from that of the first patterned region 932. However, the sheet resistivities of the second and third patterned regions 934, 936 do not have to be the same—they may differ from each other. It is understood that the difference in sheet resistivities between one patterned region and another is the result of differences in hole sizes, hole shapes and/or hole center spacings, all as discussed above. Furthermore, this holds for all the other buses 940, 950, 960 and 970.
The second bus 940 comprises a first patterned region 942 that adjoins both the second junction strip 904 and the third junction strip 906, a second patterned region 944 that adjoins the second junction strip 904, and a third patterned region 946 that adjoins the third junction strip 906.
It is noted here that the second junction strip 904 provides a region where the current turns, as indicated by arrow 905, from first bus 930 to second bus 940. The patterned regions 936 and 944, both of which adjoin the second junction strip 904, have higher sheet resistivity than the first patterned regions 932, 942, respectively, in their respective buses 930, 940. This helps reduce the formation of hot spots and cold spots in various portions of the second junction strip 904 and also in portions of the buses 930, 940 proximate the second junction strip 904.
The second heating element 992 includes third bus 950, fourth junction strip 908, fifth junction strip 910, fourth bus 960, sixth junction strip 912, fifth bus 970 and seventh junction strip 914.
The third bus 950 comprises a first patterned region 952 that adjoins both the fourth junction strip 908 and the fifth junction strip 910, a second patterned region 954 that adjoins the fourth junction strip 908, and a third patterned region 956 that adjoins the fifth junction strip 910.
The first heating element 990 and the second heating element 992 are electrically connected to one another via a thermal fuse 982, which typically is a fusible conductor bridging third junction strip 906 and fourth junction strip 908. The patterned regions 946 and 954 on either side of the thermal fuse 982 help ensure more uniform current flow in the adjacent junction strips 906, 908 belonging to buses 940, 950, respectively.
The fourth bus 960 comprises a first patterned region 962 that adjoins both the fifth junction strip 910 and the sixth junction strip 912, a second patterned region 964 that adjoins the fifth junction strip 910, and a third patterned region 966 that adjoins the sixth junction strip 912.
The fifth junction strip 910 provides a region where the current turns, as indicated by arrow 911, from third bus 950 to fourth bus 960. The patterned regions 956 and 964, both of which adjoin the fifth junction strip 910, have higher sheet resistivity than the first patterned regions 952, 962, respectively, in their respective buses 950, 960. This helps reduce the formation of hot spots and cold spots in various portions of the fifth junction strip 910 and also in portions of the buses 950, 960 that are close to the fifth junction strip 910.
The fifth bus 970 comprises a first patterned region 972 that adjoins both the sixth junction strip 912 and the seventh junction strip 914, a second patterned region 974 that adjoins the sixth junction strip 912, and a third patterned region 976 that adjoins the seventh junction strip 914.
The sixth junction strip 912 provides a region where the current turns, as indicated by arrow 913, from fourth bus 960 to fifth bus 970. The patterned regions 966 and 974, both of which adjoin the sixth junction strip 912, have higher sheet resistivity than the first patterned regions 962, 972, respectively, in their respective buses 960, 970. This helps reduce the formation of hot spots and cold spots in various portions of the sixth junction strip 912 and also in portions of the buses 960, 970 that are close to the sixth junction strip 912.
The seventh junction strip 914 provides a region where the current turns, as indicated by arrow 915, from fifth bus 970 as it travels down an elongated portion of the seventh bus towards second electrical contact 984. The third patterned region 976 of the fifth bus 970 which adjoins the seventh junction strip 914, has a higher sheet resistivity than the first patterned region 972 of the fifth bus. This helps reduce the formation of hot spots and cold spots in portions of the seventh junction strip 912 and also in portions of the fifth bus 970 that are close to the seventh junction strip 914.
The second electrical connector 984 is in communication with the seventh junction strip 914 and provides a second terminal for connecting to a power supply. The seventh junction strip 914 is provided with the elongated portion so that the second electrical contacts 984 is in close physical proximity to the first electrical contact 980. Thus, the first and second electrical contacts 980, 984 are sufficiently close to one another that they are connectable to corresponding contacts of a power cable having two or more wires.
As seen in the assembly of
People skilled in the art know how to make and use electric heaters for aircraft de-icing and other applications, as exemplified by U.S. Pat. Nos. 5,475,204, 5,590,854, 6,027,075, 6,237,874 and 6,832,742, all of whose contents are incorporated by reference to the extent necessary to understand the present invention.
The above description of various embodiments of the invention is intended to describe and illustrate various aspects of the invention, and is not intended to limit the invention thereto. Persons of ordinary skill in the art will understand that certain modifications may be made to the described embodiments without departing from the invention. All such modifications are intended to be within the scope of the appended claims.
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|US7763833 *||Mar 14, 2005||Jul 27, 2010||Goodrich Corp.||Foil heating element for an electrothermal deicer|
|US7923668||Apr 10, 2007||Apr 12, 2011||Rohr, Inc.||Acoustic nacelle inlet lip having composite construction and an integral electric ice protection heater disposed therein|
|US9067679 *||Dec 28, 2012||Jun 30, 2015||Aerospace Filtration Systems, Inc.||Heated screen for air intake of aircraft engines|
|US20140077039 *||Dec 28, 2012||Mar 20, 2014||Aerospace Filtration Systems, Inc.||Heated Screen For Air Intake Of Aircraft Engines|
|Cooperative Classification||H05B2203/003, H05B2203/011, H05B2203/026, H05B3/342, B64D13/08, H05B2203/017, B64D15/12, H05B3/34, H05B3/36|
|European Classification||B64D13/08, H05B3/34B, H05B3/34, H05B3/36, B64D15/12|