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RELATED PATENTS  
       [0001]    This patent application is related to my previously issued U.S. Pat. No. 5,813,184 for HEATED SERIALLY CONNECTABLE ROOFING SHINGLES, issued Sep. 29, 1998 which is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to electrically heated roofing shingles. More particularly, the invention provides an improved way for supplying electrical power to electrically heated roofing shingles which facilitate rapid installation and reliable operation of the shingles.  
           [0004]    2. Description of the Prior Art  
           [0005]    Buildings having pitched roofs and located in areas of high snowfall are susceptible to damage occurring from accumulated snow or other frozen precipitation on their roofs. Thermal expansion and contraction of ice caused by temperature changes may cause physical damage to the roof surface itself or to underlying structural elements. More importantly, however, is the damage caused by infiltration of water resulting from melting of snow and/or ice which backs up under the snow pack on the building roof behind ice dams near the eves of the building.  
           [0006]    It is common in northern regions to attempt to abate these problems by installing heating elements such as heating cables or tapes directly on top of the roof. These solutions have, by and large, been only moderately successful. Several heating devices specifically designed for combating the specific problems facing shingled roofs have also been proposed.  
           [0007]    One solution is described in U.S. Pat. No. 2,699,484 for DEICER FOR ROOFS, issued Jan. 11, 1955 to H. L. Michaels. MICHAELS teaches a heating devices intended for installation along the lowest edge of a roof. Unlike the roof heating system of the present invention, the MICHAELS system provides heat only along a narrow band near the edge of the roof. These types of solutions are generally considered ineffectual in preventing ice damage and water infiltration. The inventive system, using heated roofing shingles, provides heat for several courses of shingles up the roof which is very effective in preventing problems caused by ice dams near or at the edge of the roof.  
           [0008]    Two patents, U.S. Pat. No. 3,691,343 for MODULAR SYSTEM OF ROOF HEATER SHINGLES, issued Sep. 12, 1972 to Victor B. Norman and U.S. Pat. No. 3,129,316 for HEATING ELEMENT FOR ELIMINATING ICE FROM A ROOF, issued Apr. 14, 1964 to F. N. Glass, et al. teach shingle-like heating elements for installation along the lowest edge of a building roof. While these kinds of solutions typically are more effective than that of MICHAELS, in that they heat a larger surface of the roof, they still fall short of the effectiveness of the inventive system. The system of the present invention allows a varying number of courses of heated shingles to be applied, the number of courses being selected based on the environment, the roof pitch, etc.  
           [0009]    U.S. Pat. No. 2,546,743 for ELECTRICALLY HEATED DEICING SHINGLE, issued Mar. 27, 1952 to J. L. Harrison teaches a conventional style roofing shingle having an embedded resistance heating element. Each shingle must be individually connected to a power line running above and along the long axis of the course of singles. Installation requires that two electrical connections per shingle be made in situ thus requiring a competent, usually licensed electrician as well as a roofer to complete the installation. Because of the environment, each connection is subject to thermal stress which may result in electrical connection failure during the operating lifetime of the roof. The inventive heated roofing system, on the other hand, utilizes high-reliability, slip-on connectors on each shingle adapted to interact with mating connectors on a pre-assembled, flat power cord. The roofer may then both physically install the shingles and easily and competently make the electrical connections between the shingle and the power line.  
           [0010]    Finally, U.S. Pat. No. 5,813,184 for HEATED, SERIALLY CONNECTABLE ROOFING SHINGLES, issued Sep. 29, 1998 to the Applicant, teaches heated roofing shingles having electrical connectors disposed on extended tabs at each edge of the shingles. During installation, the connector on the abutted edges of adjacent shingles readily connect to one another thereby establishing a serial connection across the width of the roof. While the system is easy to install and the electrical connections provided have proven to be reliable, the performance of the roof heating varies as the number of shingles in the serial chain varies. The system of the instant invention overcomes this situation by providing a parallel electrical connection to each shingle. The ease of installation is maintained by providing a pre-assembled, flat power cord having slide-on connectors space periodically along its length offering a connection point for each shingle.  
           [0011]    None of the above inventions and patents, taken either singly or in combination, is, however, seen to anticipate or suggest the instant invention as claimed.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention relates to electrically heated roofing shingles having slide-on electrical connectors adapted to mate with compatible connectors spaced at regular intervals (e.g., 36 inches for standard shingles) along a flat, pre-assembled electrical power cable. Because the power cable is flat, it lies well under the courses of shingles. The system allows rapid installation of the roofing shingles without the assistance of an electrician. The flat cable may be folded over so as to reverse the direction of its run, thereby servicing multiple row (courses) of shingles. The power cable made by supplied in various lengths for use with different width roof installations. The connections made are reliable and the connector components used are typically approved by appropriate agencies such as the Underwrites Laboratory, etc.  
           [0013]    Accordingly, it is a principal object of the invention to provide electrically heated roofing shingles having pre-installed, slide-on electrical connectors.  
           [0014]    It is another object of the invention to provide an electrically heated roofing shingle system where each shingle plugs into a mating connector on a flat, pre-assemble power cable or cord.  
           [0015]    It is a further object of the invention to provide an electrically heated roofing shingle system where the flat, pre-assembled power cable may be folded to change its direction of travel.  
           [0016]    Still another object of the invention is to provide an electrically heated roofing shingle system where a single flat, pre-assemble power cable can provide power to multiple rows of shingles.  
           [0017]    An additional object of the invention is to provide an electrically heated roofing shingle system where the flat, pre-assemble power cord is readily connected to a source of electrical power.  
           [0018]    It is again an object of the invention to provide an electrically heated roofing shingle system which has a thermostat to control operation of the shingle heating system.  
           [0019]    These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:  
         [0021]    [0021]FIG. 1 is a top plan view of a roofing shingle of the prior art;  
         [0022]    [0022]FIG. 2 is a top plan view of the electrically powered resistance heating element of the invention;  
         [0023]    [0023]FIG. 3 is a rear plan view of a shingle showing the heating element of FIG. 2 attached to the shingle;  
         [0024]    [0024]FIG. 4 is a front plan view of the shingle shown in FIG. 3;  
         [0025]    [0025]FIG. 5; is an environmental view of a portion of a roof structure showing a first course of shingles installed;  
         [0026]    [0026]FIG. 6 is an environmental view of the roof portion of FIG. 4 but having a second course of shingles installed;  
         [0027]    [0027]FIG. 7 is a schematic view of a controller suitable for use with the inventive heated shingle system; and  
         [0028]    [0028]FIG. 8 is a cross-sectional, schematic view of a precipitation sensor for use with the controller of FIG. 7.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    The present invention relates to a heated roofing system constructed from roofing shingles having built-in electrically powered resistive heating elements. The shingles of the invention are installed in a similar manner to regular roofing shingles but are each connected to a special electrical supply cable.  
         [0030]    Referring first to FIG. 1, there is shown a top plan view of a typical asphalt roofing shingle  100  as is well known in the roofing art. Shingle  100  has a top edge  102 , a left edge  104 , a right edge  106  and a bottom edge  108 . A horizontal centerline  110  separates an upper, unexposed portion  112  of shingle  100  from a lower, exposed portion  114 . Typically, lower, exposed portion  114  carries a surface wear treatment (not shown). Optionally, slits  116  may also be provided in a wide variety of configurations also well know to those skilled in the roofing arts. Modern shingles typically omit slits  116 .  
         [0031]    While asphalt shingles have been chosen for purposes of disclosure, the invention is by no means considered limited to this type of shingle. It will be obvious that the inventive system could be applied to shingles made from wood, metal, tile, slate, or any other material suitable for forming roofing elements. The inventive system could also be applied to roofing elements in form factors other than shingles.  
         [0032]    Referring now also to FIG. 2, there is shown a top, plan view of a planar heating element  120 . A thin substrate  122  has a resistive element  124  disposed on its top surface. Resistive element  124  consists of a continuous electrical conductor having a specific resistance per unit length. Resistance element  124  could be formed by depositing a continuous filament of a small diameter (i.e., high AWG number) conductor made from nickel-chromium or a similar material well known to those skilled in the art. In a preferred embodiment, resistance element  124  is formed using printed circuit fabrication techniques. While a simple serpentine pattern has been shown for purposes of disclosure, it will be obvious that any pattern which provides an appropriate conductor length on substrate  122  could be chosen. The material used for substrate  122  is typically a flexible, heat resistant, polymer. Each end of resistive element  124  terminates in an electrical lead  126 . The routing and termination of electrical leads  126  will be described in detail hereinbelow.  
         [0033]    Heating element  120  is sized to approximately match the size of lower, exposed region  114  of shingle  100 . If shingle  100  carries optional slits  116 , resistance heating element  124  could be disposed in a pattern to avoid slits  116 .  
         [0034]    Referring now also to FIG. 3, there is shown a rear plan view of shingle  100  and heating element  120 . Heating element  120  is adapted for attachment to the rear surface of shingle  100  directly behind lower, exposed region  114 . Heating element  120  may be attached to shingle  100  in a variety of ways. Typically either a thin adhesive or double back tape could be used. A variety of other ways well known to those skilled in the art could also be used to join heating element  120  to shingle  100 . Leads  126  connected to resistance element  124  are routed through holes  128  in shingle  120  where they are terminated in slide-on connectors  142  (FIG. 4), typically female. While female connectors on the shingles and male connectors on the power cable have been chosen for purposes of disclosure, it should be obvious that the genders could readily be reversed to meet a particular operating requirement or circumstance. Leads  126  may be restrained against the rear surface of shingle  100  as required. It should be obvious that heating element  124  could easily be made integral with shingle  140 . Typically, the heating unit  124  would be sandwiched between a front and a back layer of asphalt or similar shingle base material or imbedded within a layer in the manufacture of the layer. While custom manufacturing would be required, heating unit  124  would probably be better protected during the handling of shingles  140  prior to their installation.  
         [0035]    Referring now to FIG. 4, there is shown a top, plan view of the shingle  140  of the instant invention. Female slide-on connectors  142  are shown disposed in upper, unexposed region  112  of shingle  140 . One connector system found suitable for use in this application is the Pan-Term® series from Panduit®. The male slide-on connector chosen for purposes of disclosure is a Panduit® non-insulated, butted seam male disconnect. Other similar connector systems could, of course, be substituted to meet a particular operating circumstance or environment. Male slide-on connector  142  is adapted to mate with a compatible female connector (not shown) as will be described in detail hereinbelow.  
         [0036]    Referring now to FIG. 5 there is shown an environmental view showing an array of shingles  140  on a portion of a roof of a building. The inventive heated shingles  140  are designed to work in a system with a uniquely configured power cable  150  as shown in FIG. 5. Shingles  140  are adapted for placement on the roof of a structure in much the same manner as normal roof shingles. Care must, of course, be taken to avoid inadvertently severing resistance element  124  (FIG. 3) or leads  126  (FIG. 3) with a nail, staple or other fastener. Power cable  150  is shown running along and above the course of shingles  140 . A distal end  158  of cable  150  is adapted for connection to a source of AC power, usually through a suitable controller  200  (FIG. 7). A suitable plug or interconnection means (not shown) would typically be provided. The plug or interconnection means form no part of the instant invention and suitable plugs or other interconnection means are well know to those skilled in the electrical arts. Electrical drop-down leads or pigtails  152  descend from cable  150  at regular intervals. The interval is chosen to match the width of the shingles being powered, typically 36 inches. It will be obvious that other length shingles could be used and the spacing of pigtails  152  along cable  150  could be adjusted accordingly. Each pigtail  152  terminates in an insulated slide-on connector  154 , typically male and adapted to slidably connect to female connectors  142  (FIG. 4) on each shingle  140 . Cable  150  is a flat, ribbon-type cable which allows it to be laid along and below courses of shingle without causing an excessive bulge or ridge. This helps not only protect cable  150  but minimizes potential damage to the shingles themself on roofs where people occasionally must walk. The flat construction of cable  150  also allows it to be folded so as to change its direction of travel at a corner  156 . This allows a single cable  150  to service more than one course of shingles. When the cable reaches the end of a first course, it is folded, run up (or down) to the next course, folded again and continued in a reversed direction along the next shingle course. Cable  150  is preassembled and typically supplied in a roll. As a course of shingle is fastened to the roof, the cable  150  is unrolled enough to connect each subsequent shingle. This process is continued until the end of the course is reached.  
         [0037]    Referring now to FIG. 6, there is shown the roof segment of FIG. 5 but with a second course of shingles  140  in place. Cable  150  is shown twice folded and connected to shingles  140  of the second course. As is common practice, the second course of shingles overlap the first course of shingles top-to-bottom along a horizontal dividing line  110  (FIG. 1) and are also offset left-to-right approximately one half a shingle width. Cable  150  is folded again at a second corner  160  and, by using pigtails  152  and connectors  154 , electrically connecting the shingles  140  of the second course. Additional shingle courses (not shown) could be added, the number required depending upon the typical weather (i.e., temperature, precipitation, etc) and the architectural features of the roof. As many shingle courses as required to prevent ice dams, etc. may be used, two courses being shown only for purposes of disclosure.  
         [0038]    It is preferable that the novel roof heating system include a controller. Referring now to FIG. 7, there is shown a schematic diagram of a possible controller  200  suitable for use with the inventive system. AC line power is supplied to controller  200  at terminals labeled L 1  and L 2 . A temperature sensor  202  is located so as to sense outside temperature. When the sensed temperature falls below a predetermined, usually sub-freezing design value, the contacts of temperature sensor  202  close and power is applied to the coil of first relay  204  and first relay  204  is activated. The activation of first relay  204  closes a first normally open contact  206  thereby applying electrical power to a small heating element  208  disposed in a precipitation sensor  210 . Referring now also to FIG. 8, there is shown a detailed, cross-sectional view of precipitation sensor  210 . Precipitation sensor  210  includes a sampling receptacle  218  open to the atmosphere and fixed to the protected building (not shown) in a position to collect precipitation (not shown). The floor  220  of receptacle  218  contains two electrical terminals  222 ,  224  and a heating element  208 . When precipitation (not shown) is collected within receptacle  218 , it is melted by heating element  208 . In liquid form, the precipitation spans and connects terminals  222  and  224 , thereby completing an electrical circuit. A second relay  214  is connected is series with contacts  222 ,  224  of precipitation sensor  210  and a second contact of first relay  204  such that if relay  204  has been actuated because the outside temperature is below the predetermined value, precipitation in receptacle  218  is melted by heating element  208 . Any significant build-up of liquid from the melted precipitation completes a circuit across contacts  222 ,  224  and actuated second relay  214 . It should be obvious that either second relay  214  must be highly sensitive in order to react to a potentially small current flow or that precipitation sensor  210  must itself be designed to facilitate current flow when melted precipitation is present. Temperature sensors, such as thermal switches, and precipitation sensors are well known to those skilled in the electrical arts and suitable units may readily be selected for use in controller  200 . For example, precipitation sensor  210  may operate on principles other than connection of two terminals by melted precipitation. Sensor  210  could, for example, use a capacitance based switch responsive to accumulation of melted precipitation within receptacle  218 . Finally, a contact  216  of second relay  214  is closed which allows power to be supplied to cable  150  and, in turn, to heated shingles  140  as has been described in detail hereinabove. In operation, only the combination of both sub-freezing temperatures and the sensing of precipitation causes controller  200  to provide power to the heated shingles  140  via cable  150 .  
         [0039]    It will be obvious to those skilled in the electrical design arts that numerous other possibilities exist for implementing a control circuit to perform identical or similar functions as controller  200  described for purposes of disclosure. For example, a proportional controller using a thermistor or similar temperature sensing element could be used to provide a varying amount of power to shingles  140  depending on the sensed temperature. A micro-processor based controller could also be used. In a micro-processor based controller, sophisticated algorithms could be embedded in a memory device to allow the controller to be respond to sensed environmental conditions. Additional environmental sensors could also be added in addition to the temperature and precipitation sensors disclosed.  
         [0040]    Various connectors may be used to connect controller  200  to the AC power lines and/or to connect flat cable  150  to controller  200 . Suitable connectors are also well known to those skilled in the electrical design arts and form no part of the instant invention.  
         [0041]    A main power switch (not shown) may be provided to break one or both legs of the AC supply circuit. Breaking both legs is preferable because it provide greater safety. Breaking both legs would, for example, be desirable in electrical supply circuits wherein the voltage of each leg differs in potential with neutral or ground, as commonly occurs in 240 volt, single phase residential circuits. Also, a ground-fault interrupter (GFI) could be included in the power circuit to protect the system from even small leakage current which could potentially pose a threat.  
         [0042]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Summary:
The present invention features a heated roofing system using standard-size roofing shingles each having a resistive heating element. Each shingle is designed to easily connect to a preassembled, flat electrical power cable having slide-on electrical connectors spaced periodically along its length. The power cable is typically supplied rolled so that as each shingle in a course is attached to a roof, the power cable can be unrolled and each subsequent shingle electrically connected to the cable. A power controller having a temperature sensor and a precipitation sensor controls the flow of electrical energy to the shingles. Because the power cable is flat, it lies well beneath layers of shingles and may be folded at the end of a course so that a single cable may supply power to multiple rows of shingles.