A de-icer formed of a solid block of a pressed, granulated salt has at least a top portion water-proofed to prevent rapid deterioration due to precipitation. An exposed bottom surface is in contact with the upper surface of a flat, sloped roof to provide wicking absorption of water flowing down the roof into the salt. Absorption of water by the salt leads to release of the resulting saline solution to the surface of the roof, preventing formation of ice on the roof downstream of the de-icer and in the roof drain. The de-icer may be maintained in place on the surface of the roof by an adhesive tape, or by its own weight.

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 09/318,896, filed May 26, 1999 now U.S. Pat. No. 6,282,846. 
    
    
     SUMMARY 
     The present invention relates to a method and apparatus for preventing ice from forming at a roof drain and for preventing the build-up of ice and/or snow in the region of a roof drain which, in turn, assures flow of water accumulating on the roof, down the drain. This is accomplished by affixing a partially perforated waterproof container within which salt is packed, on the surface of the roof such that water flowing down the roof is drawn into the salt and subsequently gravity discharged onto the roof, flowing toward the roof drain and downspout system, mixing with water, snow and/or ice in the region of the roof drain to melt the snow and ice and thereby prevent the build up of ice at or over the roof drain which would, in turn, result in blockage of the roof drain. 
     BACKGROUND 
     The Roof Drain De-icer Apparatus is a gravity-fed, ice melting system designed to prevent the formation of ice dams at the lower part of flat and/or inclined roofs and ice build-up and water accumulation in the roof drainage system. Ice dams are a cumulative build-up of ice at the gutter and roof drain areas of roofs, which form as a result of the daily thawing and re-freezing of the snow and ice on the roof surface. Accumulation of ice in the region of the roof drain blocks the runoff of melted water off the roof, which makes the ice dam situation more problematic. When the roof drain is blocked with ice or frozen water, the down spouts, gutters and drain box fill up with water which expands when the water freezes causing damage to the roof and the drainage system and the components thereof. Installation of a Roof Drain De-icer system of the present invention prevents this damage. The Roof Drain De-icer apparatus becomes non-operational when the water or snow on the surface of the roof upstream of the De-icer Apparatus freezes. 
     Means for de-icing or for preventing the formation of ice on the surface of a flat, sloped roof and in the roof drainage system through which water flows, is described in the prior art. However, such teachings are clearly distinguishable from the present invention. 
     The Park U.S. Pat. No. 133,247 utilizes alum and salt to saturate the roof sheeting and to also saturate the felt roofing paper. Several layers of felt roofing paper saturated with alum and salt, as well as a layer of dry salt and resin and tallow are installed prior to the installation of the roof tiles. In Park, the layer of dry salt as well as the felt roofing paper and the sheeting saturated with alum and salt do not draw water from the surface of the roof and is distinguishable from the present invention. Also, replacement of the alum and salt requires removal of the roof tiles, which is highly impractical. 
     The Anderson U.S. Pat. No. 4,041,656 discloses a device for draining melting snow. Noting FIGS. 1 through 5, Anderson provides a collection tube  12  open at each end and provided with an inner-tubular portion  24  telescopingly received within tubular portion  14  to change the overall length. A screen  40  is provided within the collection tube  12  and is filled with salt. Screen  50  has an end portion  49  which maintains the salt within the screen. Gutter members  7  and  80  are arranged to form a V shape for directing water to the upper open end of the device. The water passes into and through the device beneath the screen but remains in a liquid state. The water runs outwardly from the lower end of the device. Anderson describes that when the water freezes to ice it reaches screen  50 , causing the salt to melt the ice during the following day when melting again occurs and water runs over the ice formed in the tube causing the ice to melt. There is no teaching of water or melting snow flowing down a roof surface to a salt reservoir, which draws water into the salt to produce a saline solution within the reservoir and gravity flow of the saline solution from the reservoir onto the surface of the roof to mix with and melt snow and/or ice, preventing blockage of the drainage system as disclosed in the present invention. 
     The Guth U.S. Pat. No. 3,771,188 discloses a portable device having electric heating tiles  4  and  18  as well as a device for dispensing “a melting aid”. The Guth device is held above a region where ice is formed and cord  8  is pulled in a direction shown by an arrow in FIG. 2 to open gate  14  and dispense the material. Although Guth describes the invention as being usable on a roof of a building, the structure is intended to be manually operated, the material is dispensed to melt ice and there is no teaching of drawing snow, ice or water into a salt-filled enclosure and subsequent production and release of a saline solution from within the enclosure onto the roof. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a novel method and apparatus for de-icing a roof drain. The invention, in one preferred embodiment, comprises a container fabricated of a sleeve of waterproof material defining a hollow interior space. Portions of the upper and lower surfaces of the container are perforated with small holes. Rock salt, common salt or other stable, solid material capable of melting snow and ice, is packed in the annular space of the container. The free ends of the container are affixed to the surface of the roof adjacent to the roof drain with the perforated surface portions of the container being arranged in contact with the roof surface in the upstream direction relative to the flow of water toward the roof drain. The lower surface of the container engages the surface of the roof. 
     Water, snow or ice in the region of the upper and/or lower perforated regions are drawn into the container by the salt, forming a saline solution. Salt within the container dissolves into the water, which subsequently drains out from the perforations as a saline solution which flows along the roof toward the roof drain preventing formation of ice downstream of the de-icing apparatus and in the region of the roof drain. The saline solution combines and mixes with water in the region between the De-icer and roof drain to facilitate melting and/or prevent freezing. 
     OBJECTS OF THE INVENTION 
     Ice build up in roof drainage systems and especially roof drains causes ice and melting snow on the roof to block the flow of water, causing the roof drain to overflow, resulting in possible deterioration and structural damage to the roof and the building structure therebeneath. Also, accumulated water in the roof drain freezes, causing damage to the gutter, downspout and roof drainage system. 
     It is therefore one object of the invention to provide a novel method and apparatus for maintaining the roof drain free of ice and prevent ice and water build-up in the roof drain system and on the roof. 
     Another object of the present invention is to maintain the surface of the roof, downstream of the de-icing apparatus, free of ice. 
     Still another object of the present invention is to provide a novel roof de-icer apparatus in broken-down, compact kit form and which is easy to assemble and put into use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a side view of the waterproof container of the present invention, when empty, showing a portion of the lower perforated surface of the container when filled with salt, showing the dotted lines at which the container is tied off near the ends thereof by suitable ties and further showing a portion of the upper surface of the container when filled with salt. 
     FIGS. 1 b  and  1   c  are top and bottom views of the waterproof container of FIG. 1 when filled with salt. 
     FIG. 2 is a cross-sectional view of the container of FIG. 1 a  resting on a roof surface and looking in the direction of arrows  2 - 2 ′ of FIG. 3, the container being packed with salt, each end of the container being tied with a cable tie along the dotted lines shown in FIG. 1 a  after salt is filled in the container between the dotted lines. 
     FIG. 3 is an elevational view of the container of FIG. 2 packed with salt and positioned on a roof surface and looking in the upstream direction at the downstream side of the container. 
     FIG. 4 shows one of the ties utilized to close off the ends of the container of FIG. 1 a.    
     FIG. 5 is an elevational view of the container of FIG. 1 a  shown arranged on a roof surface and looking downstream in the direction of the upstream side of the container. 
     FIG. 6 is a perspective view showing another preferred embodiment of the present invention. 
     FIG. 6A shows the embodiment of FIG. 6 arranged along a sloping roof adjacent a roof drain. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 a  shows an elevational view of container  10  substantially comprised of upper surface  11  and lower surface  12 , formed of a waterproof plastic material of a suitable gauge to withstand the elements throughout a winter season, for example. Dotted line L represents the imaginary dividing line between the upper half  11  and the lower half  12  of the container  10 . The container is preferably formed of a substantially transparent plastic but may be translucent or opaque, if desired. In use, the container  10  is positioned so that the surfaces  11  and  12  are arranged one above the other, with surface  12  resting upon the roof (see FIGS. 2,  3 , and  5 ). Surfaces  11  and  12  may be formed of sheets which are bonded along their longitudinal side edges to create a sleeve defining a hollow interior space. Alternatively, the sleeve may be produced so as to be seamless, or may be folded over and joined along one longitudinal seam. The lower surface  12  is perforated at regular intervals with small holes  12   a  (FIGS. 1 a - 1   c ). 
     FIGS. 1 b  and  1   c  are plan views of the upper and lower surfaces. The two surfaces (sheets), in one embodiment, are integrally joined at opposite sides along their length and their ends are left open to permit the annular space created therein to be packed with salt. One of the ties  14  (see FIG. 4) is employed to close off the container near one end thereof. The container is then filled with salt. Subsequent to filling the hollow interior space with salt, the opposite end of the container is closed employing the remaining ones of the ties  14 . The ties  14 ,  14  are positioned along the dotted guide lines  15  and  16  (shown in FIG. 1 a ). Procedurally, one end of sleeve  10  is closed using one of the ties  14 . The ties  14  (see FIG. 4) are knurled along surface  14   a  forming a saw-tooth-like surface. One end  14   b  of the tie is provided with an opening  14   c , through which the end  14   d  is inserted. The tie is pulled tight, closing one end of the container  10 . The opening  14   c  is designed to prevent the end  14   d  from being pulled out of the opening, as is conventional. However, any other suitable ties may be utilized, if desired. The dotted lines  15 ,  16  printed on the container, serve as guides to identify where the ties should be located and the level to which the salt should be filled. With one end of the container being closed, the container is filled with rock salt or other suitable granular material suitable for melting snow and ice and/or significantly lowering the temperature at which water freezes. The still-open end of container  10  is then sealed using the remaining tie, placed at guide line  16 . 
     FIG. 3 shows a sectional view of the waterproof container packed with salt S. The ends of the flexible container are tied with cable ties  14 ,  14  to retain the salt within the container (see FIGS. 1 b ,  1   c , and  3 ). 
     FIG. 2 shows a sectional view of the waterproof container packed with salt  3 , the container with salt positioned on a somewhat inclined portion of a roof R adjacent to a roof drain  19  with the lower surface  12  resting on the roof and perforated surface portion  12   a  of the container being arranged so that as many of the openings  12   a  as is practicable are on the bottom and facing the surface of the roof. 
     The invention comprises an apparatus for use on a roof comprising a water-proof container which may be of any shape. The lower surface  12  of the container (which is placed in contact with the surface of the roof R), is perforated at regular intervals with a plurality of relatively small holes  12   a  as shown in FIGS. 1 b ,  1   c , and  3 . The container is filled, preferably with common salt or rock salt  3  (or other granular material suitable for melting ice) and the ends of the container are tied with cable ties  14  or other securing means to retain the salt within the container as shown in FIG.  3 . 
     The container may be generally cylindrical, spherical or rectangular in shape. The container may be fabricated of a flexible material such as a sheet of plastic or from a rigid material such as rigid plastic or polyfoam. Since the material is quite flexible, it is quite simple to substantially “flatten” the upper and lower surfaces. The ends E 1 , E 2  of the container are held against the roof by a suitable adhesive tape epoxy or glue  21 ,  22 , (preferably water-proof) able to withstand the elements normally encountered during the winter months. 
     As the water or melting snow flows along the roof, generally in the direction of flow F, it comes into contact with the perforated surface  12  and is drawn through the perforations  12   a  and into the interior of the container by the absorbing action of the salt packed in the interior space of the container. Some of the salt dissolves in the water, producing a saline solution which subsequently flows out through the perforations  12   a  and onto the surface of the roof R, and eventually towards the roof drain  19 . The dissolved salt in the saline solution reduces the freezing point of water to below 30 degrees Fahrenheit and prevents melting snow or fresh snow from freezing in the gutter and roof drain  19 . The water carrying the dissolved salt flows beneath and/or around the container  10 . The small openings in the lower surface  12  of the container substantially retains the salt within the container while allowing the water to be initially drawn into the container and thereafter the saline solution to freely flow into and out of the container. In the preferred embodiment, the openings  12   a  have a diameter of the order of {fraction (3/16)} inch. Limiting the perforations  12   a  to the downstream portions of surfaces, as opposed to providing spaced openings of substantially the entire area of surfaces  11 ,  12  increases the useful operating life of the de-icer without reducing operating efficiency. 
     A similar action takes place on upstream surface  11  wherein water, snow or ice enters perforations  12   a , being drawn by the salt S into the interior of the container. The container filled with salt S is held on the surface of the roof R by an adhesive tape or removable adhesive epoxy or glue applied in the regions  20 ,  21  (see FIG.  5 ). Alternatively, heavy objects, such as bricks B may be placed upon regions  20 ,  21  to hold the container in place. 
     The roof de-icer apparatus  10  thus prevents the formation of ice dams in the region of the roof and gutter adjacent to the roof drain whereby melting snow and ice would otherwise tend to accumulate and prevent the drainage of water through the roof drain  19 , and thereby preventing melting ice and water form accumulating and re-freezing in the drainage system, as well as the gutter and downspout. 
     In a preferred embodiment of the invention, a de-icer kit, adapted for sale in stores, comprises plastic sleeve  10  having perforations  12   a  along bottom surface  12 . Dotted guide lines  15  and  16  (printed in red in the preferred embodiment), arranged perpendicular to the length of sleeve  10 , and located approximately 6 inches inward from each end of the sleeve, as shown in FIG. 1 a , are provided as guides to indicate the location at which the sleeve should be closed off by the ties  14 . In addition, a line  18  (made of a contrasting color, such as blue, in the preferred embodiment) is printed along the upper side  11  of the sleeve and mid-way between the imaginary dividing lines (see line L in FIG. 1) which lie between the upper and lower sides  11  and  12  of the container  10 , the blue line  18  identifying to the installer, the top side of the container  10 . 
     The kit preferably includes a simple set of instructions which sets forth the following: 
     Place cable tie across one (red) dotted line ( 15 ) and fasten securely. 
     Fill sleeve ( 10 ) with rock salt to a level slightly below the other (red) dotted line ( 16 ). 
     Close the other end of the sleeve ( 10 ) at the second (red) dotted line ( 16 ) with the other cable tie ( 14 ). 
     Position sleeve ( 10 ) containing the rock salt with the perforations of the sleeve on surface  12  placed down and on the surface of the roof approximately one to two feet from the roof drain opening, in path of water and melting snow and positioned downstream relative to the normal flow toward the roof drain. The “blue” line  18  should be located facing upwardly (to the sky) and lie mid-way between the sides of the container (shown as imaginary line L). The container is thus placed so that the blue line is substantially equidistant from the sides of container  10 . 
     Retain both ends of sleeve ( 10 ) upon the surface of the roof with adhesive tape, enclosed. Or place a weight such as a brick B on top of each end portion of the sleeve ( 10 ) extending between the dotted lines and the ends thereof to hold container  10  in place on the surface of roof (nails brads or other piercing objects should not be used to prevent damage to the roof and to prevent the unwanted flow of water through such openings). 
     Another preferred embodiment of the present invention is shown in FIGS. 6 and 6 a  which comprises a solid block of pressed salt  30  which is coated with a water-proof material, such as wax, forming a water-proof layer along top surface  30   a  and at least partially along the upper portions of the side surfaces, such as for example, the side surfaces  30   b  and  30   c  as shown in FIG.  6 . The other side surfaces are coated in a like manner. The block of pressed salt, which is preferably in the shape of a rectangular parallelepiped, is typically of a weight which is sufficient to retain its position along a sloping roof, as shown in FIG. 6 a . The water-proof coatings reduce the loss from rain and air moisture, but does not effect the efficiency of the unit. The use of the embodiment  30 , shown in FIG. 6, greatly simplifies the portability and installation of the device as it is so to speak, fully assembled and self-ballasted, i.e., is of a weight which is sufficient to retain the member  30  on a sloping roof without the need for additional hold-down devices, adhesives, or the like. Block  30  is preferably dipped in melted wax to provide the water-proof coating, shown in FIG.  6 . However, any other suitable water-proof material capable of withstanding outdoor weather conditions may be used. The block  30  need not be a rectangular parallelepiped so long as at least one surface thereof is substantially flat. 
     It can thus be seen that the present invention provides a unique and yet simple and inexpensive apparatus and method for preventing the icing up of roofs and the blockage of gutters, downspouts, roof drains and the like. 
     A latitude of modification, change and substitution is intended in the foregoing disclosure, and in some instances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention described herein.