Abstract:
An apparatus for imparting an electric field to water travelling within a pipe. The apparatus includes a plurality of rectangularly-shaped coils of electric wire connected in an electrically parallel arrangement. Each coil is sandwiched between flexible cover sheets. The resulting assembly is applied to the outer circumference of the pipe, with the lengthwise dimension of the coil extending perpendicularly to the flow inside the pipe. A time-varying electric current is applied to the coil to produce a corresponding electric field. This, in turn, produces controlled precipitation of mineral ions from the water.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an apparatus that reduces the formation of “scale” inside pipes or vessels which carry water or other fluids and, more particularly, the invention relates to the induction coils that are wrapped around such pipes as part of the apparatus. 
     BACKGROUND OF THE INVENTION 
     The formation of scale inside of pipes that transport water and other fluids is both a common and serious problem. This holds true for industrial as well as residential applications. The reason is that most fresh water in the United States can be regarded as “hard.” Hard water contains mineral ions, such as calcium and magnesium, which are dissolved in the water but precipitate out over time onto the interior surfaces of pipes and other conduits through which the water travels. 
     More particularly, in scale formation, supersaturated mineral ions (such as calcium) in the water combine with counter-ions (such as bicarbonate) and then precipitate out of solution and deposit on scale-susceptible surfaces. 
     As scale deposits on the inside surface of the pipe accumulate, the effective diameter of the pipe is reduced, thereby restricting the flow of water. (In a vessel for holding water, scale reduces the vessel&#39;s capacity.) This is an especially acute problem when the water is used in a heat transfer situation such as a boiler. Since the scale deposits act as a heat insulator, it contributes to the further deleterious effect of reducing the efficiency of the heat transfer. This reduction can be very expensive, causing as much as 70% of the overall cost of the heating fuel to be wasted. 
     One way of dealing with scale deposits is to physically remove the deposits by such procedures as sand blasting, acid cleaning, mechanical scraping or brush punching. However, these procedures generally require at least some disassembly of the equipment in which the scale deposits have formed, with consequent interruption in the operation of that equipment, in addition to the cost of the procedures themselves. Moreover, these physical methods of removing the scale may damage the pipe or other pieces of equipment. Furthermore, certain sections of pipe may be inaccessible to a scraper or brush, making it impossible to remove the scale with a physical procedure. 
     Procedures using physically non-invasive steps are known in the art. For example, it is known to wrap a wire in an elongated, spiral configuration around a segment of the pipe, upstream from the location where the scale deposits would normally form. The spirally-wrapped wire forms an induction coil. A time-varying electric current is passed through the coil, thereby creating a time-varying magnetic field inside the segment of pipe around which the wire is wrapped. That magnetic field produces induction and this induction in turn causes the mineral ions to precipitate out of the water. This effect by an electronic descaling apparatus is called “controlled precipitation”. 
     Calcium carbonate precipitates are capable of assuming two predominant crystal structures. One of these crystal structures floats in solution and can be carried away by the water flow; the other crystal structure tends to cling to the lateral pipe surfaces and/or to sink to the bottom and hence accumulates to form the undesired deposits. 
     It is a goal in controlled precipitation to promote the first crystal structure which floats in the water. This is achieved by forming, upstream of the region of the potential scale deposits, seed crystals of the above-described structure which float in solution. These seed crystals cause subsequent mineral carbonate precipitates of the same structure to grow around them. These precipitates then pass through the (downstream) region of potential scale deposits without causing the (undesired) formation of such deposits. 
     As previously noted, a known technique for effecting controlled precipitation involves spirally wrapping an induction coil around the above-mentioned upstream portion of the pipe and energizing this coil with a time-varying electric current. This current in the induction coil creates a time-varying magnetic field inside the pipe and that field, in turn, causes induction which then in turn produces the desired controlled precipitation. 
     This known technique is relatively effective in dealing with undesired scale formation, but there are situations in which its implementation is problematic. For example, there are installations in which the diameter of the piping around which the induction coil would need to be wound is so large (as much as 84 inches in some electric power generating plants) that it would be impractical to wrap the required induction coil around the perimeter of the pipe due to its physical size and the large impedance created by the long length of wire needed to form a large diameter coil. 
     As another example, there are installations in which the piping is in such tight quarters, or so close to other equipment, that it would again be impractical to wrap the induction coil around the outer perimeter. Also, the larger the diameter of the pipe, the greater the electric current that is needed to effect the precipitation of the calcium carbonate. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a plurality of individual induction coils that are connected together in an electrical parallel connection. Each coil is comprised of a length of flat wire attached to a correspondingly flat support surface, such as a flexible sheet of plastic or nonferrous metal. To protect the flat wire from damage, it is preferably overlaid with another such flexible sheet. 
     The flat wire is formed in a substantially planar, spiral-like configuration. The turns of the spiral-like configuration are preferably not round, but are elongated in the same general direction, so as to form a coil of a generally rectangular shape, with a wire-free central portion extending lengthwise of the rectangle. 
     Thus, there is created a rectangular sandwich-like assembly of spiral-like, flat wire, flanked by cover sheets. This assembly is relatively thin (preferably only fractions of an inch in thickness). It is also flexible, since both the wires and their cover sheets are chosen so as to be inherently flexible. 
     Each individual coil is arranged so that the short side of one rectangularly-shaped coil overlays the short side of its immediately adjacent rectangularly-shaped coil. This forms a flat, elongated rectangular coil assembly which is rolled around the perimeter of the pipe segment in which the desired controlled precipitation is to be achieved. The longitudinal direction of each wrapped rectangular coil is substantially concentric with the wall of the pipe. An axis through the center of each rectangularly-shaped coil would intersect and be substantially perpendicular to the longitudinal axis of the pipe. 
     In so doing, the coil assembly is positioned so that its lengthwise dimension extends circumferentially with respect to the pipe. 
     When the coil assembly is energized by a time-varying electric current, an oscillating electric field is created through which the water flows. The oscillating electric field causes the desired controlled precipitation of calcium carbonate out of the water that flows through the pipe section around which the coil assembly is wrapped. The oscillating electric field also tends to promote the formation of the calcium crystal structure that floats in water rather than the crystal structure that accumulates. 
     Although the preferred embodiment utilizes three coils, additional flat, rectangularly-shaped coils in accordance with this invention can be added to work as intended with large-diameter pipes. By virtue of its thinness and inherent flexibility, it can readily be applied to pipes in restricted locations. When so applied, it can be held in place either by adhesive on the exposed surface of one of the plastic sheets, or by ordinary cable ties or other clamps surrounding the sandwich-like structure and any portions of the pipe circumference not covered by the sandwich-like structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description may be better understood when read in conjunction with the accompanying drawings, which are incorporated in and form a part of the specification. The drawings serve to explain the principles of the invention and illustrate embodiments of the present invention that are preferred at the time the application was filed. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
     In the accompanying drawings: 
     FIG. 1 is a perspective view of a plurality of pre-wrapped, rectangularly-shaped coils in accordance with the present invention wrapped around a pipe section; 
     FIG. 2 is a top view of one of the rectangularly-shaped coils shown in FIG. 1 laid flat and illustrating its sandwich-like structure; 
     FIG. 3A is a block diagram of the pre-wrapped, rectangularly-shaped coils shown in FIG. 1 connected in parallel to an electronic descaling unit; 
     FIG. 3B is a schematic diagram of the pre-wrapped, rectangularly-shaped coils shown in parallel in FIG. 3A connected to an electronic descaling unit; 
     FIG. 4A is a top view of one embodiment of the rectangularly-shaped coils shown in FIG. 1 laid flat; and 
     FIG. 4B is a top view of an alternate embodiment of the rectangularly-shaped coils shown in FIG. 1 laid flat, but with overlapping ends. 
    
    
     The same reference numerals are used in the several figures to designate corresponding elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In describing a preferred embodiment of the invention, specific terminology will be selected for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. Unless otherwise specified, the words “inwardly” and “outwardly” refer to radial directions toward and away from, respectively, the geometric center of a continuous pipe section to which the present invention is applied. The term “spiral-like” refers to a flat, two-dimensional configuration (in its initial shape since the two-dimensional configuration may be bent or wrapped around the exterior of the pipe). 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings in which a plurality of pre-wrapped coils connected in parallel, in accordance with the present invention, is generally indicated at  10 . 
     Referring now to FIG. 1, a preferred embodiment of a pre-wrapped coil assembly  10  is comprised of three, individual rectangularly-shaped coils  30 ,  31  and  32  that are connected together and wrapped around a pipe segment  20 . Electrical connections between the three coils  30 ,  31  and  32  are made with electrical wires and brought to terminations  14  and  15 . These terminations provide a means for connecting the coil assembly  10  to a current source  21 . The current source provides electrical current to each of the individual coils  30 ,  31  and  32  for producing an electric field in the pipe segment around which the coil assembly  10  is wrapped. As the water travels through pipe segment  20 , it is subjected to the electrical field. 
     As shown in FIG. 2, an individual coil  30  comprises a sandwich-like assembly of a support sheet  11 , flat wire  12  formed into a spiral-like shape, and cover sheet  13 . Coils  31  and  32  are substantially identical to coil  30 . However, as discussed below, each coil  30 ,  31  and  32  may have different dimensions depending on the specific application. 
     In FIG. 2, the cover sheet  13  has been shown partially peeled back in order to provide a clearer picture of the sandwich-like construction of a single coil  30 . In an actual finished assembly, this cover sheet  13  overlies flat wire  12  and support sheet  11 . 
     A sandwich-like assembly of flat wire  12  flanked by support sheet  11  and cover sheet  13  is formed by gluing the sheets together. The face of the support sheet  11  is coated with epoxy glue; the flat wire  12  is pre-shaped into its spiral-like configuration and placed on the top face of the support sheet  11 . Epoxy glue is spread on the bottom face  13   a  of the cover sheet  13 . Finally, the cover sheet  13  is placed over the flat wire  12  and support sheet  11 . 
     Flat wire  12  is preferably attached to support sheet  11  by an epoxy glue. Flat wire  12  is attached to cover sheet  13  by having the latter&#39;s face  13   a  coated with adhesive. Alternatively, a double-sided tape  12   a  underlying the coil may be used to secure the wire  12  to support sheet  11 . Adhesive tape  12   a  should have surface dimensions slightly greater than those of the spiral-like, flat wire  12 , but smaller than the surface dimensions of the respective support and cover sheets  11  and  13 . 
     The two ends of flat wire  12  are brought out to terminals  14  and  15  for connection to the electrical circuitry  21  which provides electric current and is used to energize each coil  30 ,  31  and  32 . 
     Wire  12  is made from an electrically conducting metal (preferably copper or aluminum) that has been flattened on diametrically opposite sides to reduce the overall thickness of the coil  30 . In addition to being flat, wire  12  is preferably insulated to prevent shorting between adjacent turns of the coil, and also to enable the innermost end of the flat wire to be brought out to terminal  15  across the other turns of the spiral-like flat wire  12 . 
     The wire  12  of which coil  30  is made preferably of the stranded variety, rather than solid core. This is so that the wire  12  will be relatively flexible, both in order to form the desired bends at the four corners of the rectangular coil, and to facilitate flexing of the entire assembly  10  when being applied to a pipe in accordance with the invention. 
     As can be seen from FIG. 2, the coil  30  has a generally rectangular configuration, with a long dimension (or length)  16  and a short dimension (or width)  17 . The corners of the flat wire  12  are somewhat rounded, consistent with the bending characteristics of the electrical wire  12 . As can be seen in FIG. 2, a wire-free space  12   b  preferably extends lengthwise of flat wire  12  between the legs of the innermost turn of the flat wire  12 . 
     It will be understood that the number of turns and the specific geometry of spiral-like flat wire  12 , shown in FIG. 2, are purely illustrative. In a practical embodiment, there may be many more turns, and they may be much closer to each other than shown in FIG.  2 . Indeed, adjacent turns may touch each other, the wire being insulated as noted above. Also, alternate configurations including circles, ovals and other shapes (geometric or otherwise) may be utilized depending on the specific application or environment. 
     Successful embodiments of the sandwich-like coils  30 ,  31  and  32  embodying the present invention have been constructed with the following preferred parameters for the flat wire  12  (See FIG.  2 ): 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Length 16 
                 19 inches 
               
               
                   
                 Width 17 
                 12 inches 
               
               
                   
                 Number of turns 
                 25 
               
               
                   
                 Wire size 
                 14 gauge 
               
               
                   
                 Width of tape 12a 
                  4 inches 
               
               
                   
                   
               
             
          
         
       
     
     It will be understood that still other variations will occur to those skilled in the art, without departing from the inventive concept. 
     Turning now to FIG. 3A, this shows, in a simplified diagrammatic form, the electrical connections of coils  30 ,  31  and  32  in accordance with the invention. (Note that the coils  30 ,  31 , and  32  together form the pre-wrapped coil assembly  10 .) Specifically, broken-line rectangles  30   a ,  31   a  and  32   a  respectively represent the flat rectangular outlines of coils  30 ,  31  and  32 . 
     The sandwich-like coils  30 ,  31  and  32  are oriented in the same direction (i.e., in the same longitudinal alignment) and the corresponding terminations  33   a ,  33   b  from each coil are connected in an electrically parallel connection. The terminations  33   a ,  33   b  are eventually connected to a single pair of terminals  14 ,  15  which provide an input to the pre-wrapped coil assembly  10  from the current source  21 . If additional coils are added, they will be aligned in the same longitudinal direction as the preceding coils  30 ,  31  and  32 . This ensures that the electric field generated by each coil is concentrated in the same direction. 
     Wires  30   b ,  31   b  and  32   b  are schematic diagrams of the flat coils  30 ,  31  and  32 , respectively. In FIG. 3A, only two turns are shown for each coil, but it will be understood that this is for explanation only. As indicated previously, twenty-five (25) turns are used in a preferred embodiment. 
     FIG. 3B is a block diagram of the coils illustrated in FIG.  3 A. As shown, each coil is represented by its respective impedance, Z 30 , Z 31 , and Z 32 . Since the coils are connected in parallel, the overall impedance decreases, thus producing a strong electric field in the water when the coils are wrapped around the perimeter of the pipe (i.e., 1/Z T =1/Z 30 +1/Z 31 +1/Z 32) . In the preferred embodiment, when the coils are standardized (i.e., the same length and width, number of turns, same gauge of wire, etc.,) the impedance of one coil substantially equals the impedance of the other coils (Z 30 =Z 31 =Z 32 ). 
     Referring now to FIG. 4 a , one embodiment of the physical structure of the coil assembly  10  is illustrated. Coils  30 ,  31  and  32  are manufactured as individual units. A short side of coil  30  is abutted against the opposite short side of coil  31 ; the remaining short side of coil  31  is abutted against the opposite short side of coil  32 . As illustrated, each coil is aligned in the same longitudinal direction, i.e., the wires of all coils are wound in the same direction (and preferably with the same number of turns) so that their output terminations  33   a ,  33   b  are all on the same side. 
     FIG. 4 b  shows an alternate embodiment wherein a portion of each coil overlaps each adjacent coil. In the example shown, and in keeping with the proper alignment, the left portion of coil  31  overlaps the right portion of coil  30 ; similarly, the left portion of coil  32  overlaps the right portion of coil  31 . Although, the order of overlap is not important, the alignment of each coil is important. 
     The coils of FIG. 4 b  may also be individually pre-manufactured. However, due to manufacturing costs or other reasons, it is possible to manufacture the coil assemblies  10   a ,  10   b  of FIGS. 4A and 4B, respectively, as a single unit. Specifically, turning to FIG. 4A, all three flat wires  30   b ,  31   b , and  32   b  may be placed on a single support sheet  71 . Support sheet  71  will have the same width as support sheet  11  that is used to manufacture a single coil  30 , but will be approximately three times longer. Similarly, a single cover sheet  73  may be substituted for three individual cover sheets  13 . 
     Referring again to FIG. 1, the coil assembly  10  is placed around the outside of pipe segment  20 . This pipe segment  20  contains and directs the water whose scale forming effect is to be treated in accordance with the present invention. Since each coil has the same general construction, and each is attached to the circumference of pipe  20  in the same manner, the coils should have the same orientation as shown in FIG. 3A, namely with their lengthwise dimension is perpendicular to the flow of water in pipe segment  20 . 
     As shown in FIG. 1, the coil assembly  10  preferably surrounds most of the circumference of pipe segment  20 . Indeed, the opposite ends of coil assembly  10  may actually touch, or even overlap. In fact, it is preferred that the flat wires of coil  30  overlap the flat wire of coil  32 . This would increase the over-all effectiveness of the induction created by the electric field in producing controlled precipitation within pipe segment  20 . 
     In FIG. 1, terminals  14  and  15  are shown connected to electric current source  21 . This source  21  represents the circuitry which energizes the coil  12  to produce controlled precipitation inside pipe  20 . The characteristics and operation of circuitry suitable for this purpose are known and are, therefore, not further discussed herein. For example, reference is made in this regard to co-pending U.S. patent application Ser. No. 08/544,156, filed Oct. 17, 1995, which issued into U.S. Pat. No. 5,725,778, on Mar. 10, 1998; U.S. patent application Ser. No. 08/544,026, filed Oct. 17, 1995 which issued into U.S. Pat. No. 5,670,041 on Sep. 23, 1997; and U.S. patent application No. 08/736,230, which issued into U.S. Pat. No. 5,776,334 on Jul. 7, 1998. All of the aforementioned applications are assigned to the assignee of the present invention. Each of the aforementioned three applications disclose details of circuitry suitable for use as current source  21  in FIGS. 1 and 3; their contents are incorporated in the present specification by reference, as if fully set forth at length herein. 
     As previously noted, the assembly  10  may be secured to pipe  20  by adhesive (not visible in FIG. 1) on the surface of support sheet  71  which faces away from coil  12  and toward the pipe segment  20 . It is this adhesive surface on the support sheet  71  by means of which assembly  10  is then retained against pipe  20 . 
     As previously mentioned, if adhesive attachment of the assembly to the pipe is not appropriate, mechanical attachment can be used, as by wrapping so-called cable ties around the outside of the one or more assemblies. This would be especially appropriate if there is very little space between the pipe to be equipped with an assembly embodying the invention and adjacent equipment. In that case, the assembly may have to be slid into position through a narrow gap, and adhesive on the side facing the pipe could interfere with that sliding movement. 
     Coils  30 ,  31  and  32  are preferably so dimensioned that, when applied to pipe segment  20 , they combine to encircle most of the circumference of the pipe. Preferably, the three separate coils  30 ,  31  and  32  have the same external and internal constructions and dimensions and are positioned symmetrically around the circumference of pipe  20 . 
     Referring again to FIGS. 1 and 3A, the opposite ends of coil assembly  10  are shown separated by an appreciable distance. However, this showing is only to enable clear illustration of the external connections to coil assembly  10 , including terminals  14  and  15 . In actuality, these opposite ends of assembly  10  are preferably brought as close as practical to each other. There may even be a slight overlap of each coil end, as discussed previously. 
     In the preferred embodiment of the invention, the length of each coil is substantially equal (i.e., approximately ⅓ the perimeter of the pipe  20 ). However, for a specific application, one individual coil may have a length different than that of the other two coils. In fact, all three coils may have different lengths. 
     Since pipes come in standardized diameters, it may be desirable to standardize the length of each coil in order to reduce manufacturing costs. For example, a standard length of nineteen inches for each individual coil may be used. When affixed to a sixteen-inch diameter pipe, three nineteen-inch long coils can be utilized (taking into account the overlap portion), while four coils can be used for a twenty inch pipe. 
     Referring again to FIG. 3A, the time-varying electric current provided by source  21  to terminals  14 ,  15  circulates simultaneously in one direction (e.g., clockwise then counter-clockwise, clockwise, etc.) in each coil  30   b ,  31   b  and  32   b  (as noted previously the flat wire in each coil is wrapped in the same direction). As a result, when coils  30 ,  31  and  32  are attached to pipe segment  20  as shown in FIG. 1, the electric fields created inside pipe  20  by the three coils will have the same orientation with respect to the interior of the pipe and their effects will therefore reinforce each other. 
     More than three separate coils like those in FIG. 2 can be placed around the pipe circumference. All coils should then be interconnected so that the current in all of them circulates in the same direction, and therefore produces electric fields of the same orientation with respect to the interior of the pipe. 
     Although this invention has been described and illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made which clearly fall within the scope of this invention. The present invention is intended to be protected broadly within the spirit and scope of the appended claims.