Abstract:
A heat application apparatus includes a longitudinally split cylinder that may be disposed about a section of a suspension bridge cable or similar tubular article. The cylinder is split into two essentially identical semi-cylindrical halves which are pivotally connected by an elongate hinge. A plurality of toggle clamps are arranged transversely across the opens ends of the halves and may be engaged to positively connect and lock the edges together. On each of the inner faces of the halves is secured a semi-cylindrical air bladder. The bladders are covered by a flexible heat blanket having a uniformly distributed electrical resistance heating element. Independent air pressure regulators which are supplied with compressed air provide air at low pressure to the bladders and a suitable electrical connector all reside on the exterior of the apparatus. Optionally, an air compressor may be mounted on each half to supply each regulator and bladder independently, thereby configuring the apparatus so that it requires only electrical power to operate.

Description:
FIELD 
       [0001]    The present disclosure relates to a cylindrical heat applying device and more particularly to a cylindrical heat applying device for applying pressure and heating protective coverings on suspension bridge cables and the like. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    The cables of suspension bridges and cable stayed bridges as well as similar lengthy tubular metal articles utilized outdoors are frequently subjected to severe environmental and climatic conditions. Even if conditions are relatively mild, the initial investment and the expected, extended service life demand that all practical efforts be undertaken to maintain the structure. Typically, therefore, such cables and articles are painted or otherwise coated to minimize rusting or other deterioration from such exposure. Although protected with suitable weather resistant paint or other coatings, periodic repainting or recoating of such cables and articles is invariably necessary. Such activity is costly and time consuming because of the relative inaccessibility of such cables. The cost and time involved are further increased because proper maintenance practice generally dictates removal of the previous paint or coating. Such removal typically raises environmental issues. 
         [0004]    An alternative to such repeated repainting or recoating involves permanent application of a spiral or helical wrap of a Neoprene or similar polychloroprene band or strip about the cable or article. This approach to cable protection was not without drawbacks, however. First of all, the Neoprene could not be colored and thus, after application, if it was desired that the cable covering match the rest of the structure, it would still require painting. Second of all, it was necessary to seal adjacent layers of the wrap to one another with a solvent. This again was a labor intensive undertaking. 
         [0005]    An improvement to this approach comprehends the application of a spiral wrap of Hypalon® to the cable or article. Hypalon is a registered trademark of the E. I. DuPont de Nemours Company for its brand of chlorosulfonated polyethylene. This material can be sealed to itself with the application of sufficient heat and thus eliminates the above-noted solvent sealing step. The use of a heat sealed spiral wrap of a band or strip of Hypalon® is described in detail in co-owned U.S. Pat. No. 5,390,386. Study of the subject patent reveals that proper sealing of the adjacent wraps or layers of Hypalon® is dependent upon sufficient and uniform application of heat to the exterior of the wrapped cable. 
         [0006]    Because the various strands and cables that constitute the suspension cable do not assemble and nest uniformly, the outer surface of the suspension cable is irregular. Such an irregular surface, of course, is generally duplicated by the spiral wrapped band or strip, rendering uniform heat application difficult: protruding regions are in intimate contact with a heating device and may receive excessive heat while recessed regions may not contact the heating device and thus receive little heat. The present invention is directed to ensuring the sufficient and uniform application of heat to the exterior of the wrapped cable to provide the optimum protection to the cable and therefore its longest life with reduced maintenance expense. 
       SUMMARY 
       [0007]    The present invention provides a heat application apparatus in the form of a split cylinder or clamshell that may be disposed about a section of a suspension bridge cable or similar tubular article. The cylinder is split lengthwise into two essentially identical semi-cylindrical halves which are pivotally connected by an elongate hinge. A plurality of toggle clamps are arranged transversely across the opens ends of the halves and may be engaged to positively connect and lock the edges together. On each of the inner faces of the halves is secured a semi-cylindrical air bladder. The bladders are covered by a flexible heat blanket having an electrical resistance heating element uniformly distributed over its area. Independent air pressure regulators which provide compressed air at low pressure to the bladders and a suitable electrical connector all reside on the exterior of the apparatus. Optionally, an air compressor may be mounted on each half to supply each air bladder independently, thereby configuring the apparatus so that it requires only electrical power to operate. 
         [0008]    In operation, the apparatus is connected to suitable sources of electricity and compressed air, or only electrical power if the optional air compressors are utilized. The toggles are unlatched and released and the halves are opened, placed about a cable or other article, closed and the toggles relatched. The air bladders are then filled with compressed air to a pressure of between about 1 p.s.i. and 10 p.s.i. and the heater is activated for a prescribed time to heat and seal the wrapped layers of the cable or other article. 
         [0009]    Thus it is an aspect of the present invention to provide a heat application apparatus for suspension bridge cables and similar tubular articles. 
         [0010]    It is a further aspect of the present invention to provide a heat application apparatus having a cylindrical body that is split into two semi-cylindrical halves. 
         [0011]    It is a still further aspect of the present invention to provide a heat application apparatus having a cylindrical body that is split into two semi-cylindrical halves which are pivotally joined by an elongate hinge. 
         [0012]    It is a still further aspect of the present invention to provide a heat application apparatus having a cylindrical body that is split into two semi-cylindrical halves which may be releasably closed by toggle clamps. 
         [0013]    It is a still further aspect of the present invention to provide a heat application apparatus having two semi-cylindrical halves each including an air bladder. 
         [0014]    It is a still further aspect of the present invention to provide a heat application apparatus having two semi-cylindrical halves each including a electrical heating blanket. 
         [0015]    It is a still further aspect of the present invention to provide a heat application apparatus having two-semi-cylindrical halves each having an independent air supply. 
         [0016]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, invention or claims. 
     
    
     
       DRAWINGS 
         [0017]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure, invention or claims in any way. 
           [0018]      FIG. 1  is perspective view of a cylindrical heat application apparatus according to the present invention in place on a suspension bridge cable shown in phantom lines; 
           [0019]      FIG. 2  is an end elevational view of a cylindrical heat application apparatus according to the present invention in an open position; 
           [0020]      FIG. 3  is an enlarged, fragmentary end view of a cylindrical heat application apparatus according to the present invention showing the mounting of the air bladder and heat blanket with the toggles in the locked position; 
           [0021]      FIG. 4  is an enlarged, fragmentary end view of the hinge of a cylindrical heat application apparatus according to the present invention showing the mounting of the air bladder and heating blanket; 
           [0022]      FIG. 4A  is a greatly enlarged, fragmentary, sectional view of a first embodiment of a heating blanket utilized in the present invention; 
           [0023]      FIG. 5  is an enlarged, fragmentary end view of an alternate embodiment of the heating blanket of the apparatus according to the present invention showing the mounting of the air bladder and heating blanket; 
           [0024]      FIG. 5A  is a greatly enlarged, fragmentary, sectional view of a second embodiment of a heating blanket utilized in the present invention; 
           [0025]      FIG. 6  is a fragmentary perspective view of a cylindrical heat application apparatus according to the present invention showing the air supply components; and 
           [0026]      FIG. 7  is a fragmentary perspective view of a cylindrical heat application apparatus according to the present invention showing the electrical input connector. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, invention, claims, or use. 
         [0028]    With reference to  FIGS. 1 and 2 , a cylindrical heat application apparatus for use with cables on conventional suspension bridges, cable stayed bridges and other tubular or cylindrical articles or components of indefinite length is illustrated and designated by the reference number  10 . The heat application apparatus  10  is shown in place in a suspension bridge cable  12  having a core  14  of a plurality of wound strands, ropes and cables that is spirally or helically wrapped by a strip or band  16  of a heat sealable, thermoplastic material such as Hypalon®, as described in U.S. Pat. No. 5,390,386. 
         [0029]    The heat application apparatus  10  is essentially a longitudinally split hollow cylinder or tube of a convenient length, typically between two and four feet (0.617 to 1.23 meters). The diameter, in turn, is dependent upon the outside diameter of the cable  12  or other article upon which the heat application apparatus  10  will be utilized. Typically, the nominal inside diameter of the apparatus  10  will be approximately one to three inches (25 to 76 millimeters) larger than the cable  12  or other article with which it will be utilized. Thus, it should be appreciated that the nominal diameter of the apparatus  10  may be as small as one foot (0.308 meters) or less to as large as four feet (1.23 meters) or more. 
         [0030]    The heat application apparatus  10  comprises a first or left semi-cylindrical half or portion  20 A and a second or right semi-cylindrical half or portion  20 B pivotally secured together along adjacent longitudinal edges by a preferably full length, piano style hinge  30  having a first flange  32 A attached to the first or left semi-cylindrical half or portion  20 A and a second flange  32 B attached to the second or right semi-cylindrical half or portion  20 B as will be more fully described below. Alternatively, a plurality of separate, longitudinally spaced-apart hinges may be employed to pivotally connect the first and second halves or portions  20 A and  20 B. In most respects, the first cylindrical portion  20 A and the second cylindrical portion  20 B are symmetrical, mirror images of one another. Thus, only the first or left semi-cylindrical half or portion  20 A will be fully described, it being understood that such full description applies equally to the second or right semi-cylindrical half or portion  20 B and that any differences between them are also described. 
         [0031]    The first semi-cylindrical half  20 A includes a first rigid semi-cylindrical body panel  22 A which is attached to the first flange  32 A of the hinge  30  by suitable fasteners  24  such as rivets, machine bolts and nuts, self-threading screws and the like. Depending upon the materials from which the first body panel  22 A and the first hinge flange  32 A are constructed and other design and construction considerations, more permanent attachment means such as welding may also be utilized. 
         [0032]    The first rigid semi-cylindrical body panel  22 A includes a curved outside surface  26 A and a curved inside surface  28 A. Disposed on the outside surface  26 A of the first body panel  22 A are a pair of spaced apart semi-circular braces or reinforcements  34 A. The braces  34 A each include a flat, lower portion  36 A adjacent the hinge  30  which serve as feet to maintain the apparatus  10  in an upright and non-rolling disposition for transport and when not in use. The braces  34 A are preferably secured by welding to the outside surface  26 A of the first body panel  22 A. The braces or reinforcements  34 A are intended to maintain the integrity and the circularity of the apparatus  10  against the hoop stress generated when it is in use. Accordingly, although the apparatus  10  illustrated in  FIG. 1  utilizes two of the braces  34 A, as the diameter of the apparatus  10  increases, additional braces  34 A may be both desirable and utilized. In addition to preventing longitudinal warpage of the apparatus  10 , the braces or reinforcements  34 A also function as handles which an operator can grip to maneuver the apparatus  10 . Extending longitudinally between the braces or reinforcements  34 A are a plurality of stabilizing beams or rods  38 A. Once again, while three of the stabilizing beams or rods  38 A are illustrated, more may be utilized as the size of the apparatus  10  increases. 
         [0033]    Referring now to  FIGS. 1 ,  2  and  3 , at the top of the apparatus  10 , opposite the hinge  30  are a plurality of toggle clamp assemblies  40 . On one side, for example, on the first or left semi-cylindrical half or portion  20 A are a plurality of hooks  42  arranged in a line parallel to the adjacent edge of the first semi-cylindrical body panel  22 A. On the other side, for example, the second or right semi-cylindrical half or portion  20 B are a like plurality of complementary toggle clamps  44  also arranged in a line along the adjacent edge of the second semi-cylindrical body panel  22 B. Each of the toggle clamps  44  includes a U-shaped strap  46  secured to an over-center pivoted handle  48 . To close and secure the two halves or portions  20 A and  20 B together, they are moved into the position illustrated in  FIG. 3 , the straps  46  are placed over the hooks  42  and the handles  48  are moved from the position illustrated in  FIG. 2  to the position illustrated in  FIG. 3 . 
         [0034]    Referring now to  FIGS. 3 ,  4  and  4 A, on the inside surface  28 A of the first body panel  22 A is a flexible air bladder panel  50 A. The air bladder panel  50 A is sealingly secured along the edges of the inside surface  28 A of the first body panel  22 A by a silicone adhesive  52  or similar material that provides an air-tight seal and defines a first air chamber  54 A with the first body panel  22 A. Alternatively, aluminum strips over the edges of the air bladder panel  50 A with fasteners may be utilized as a holddown. Extending over the surface of the air bladder panel  50 A is a first flexible heating blanket  60 A. The first heating blanket  60 A is preferably fabricated of a heat resistant flexible material such as silicone rubber and includes an embedded electrical resistance heating element  62 A. The heating element  62 A is preferably arranged in a zig-zag pattern in parallel strips or bands having a width of from two to three inches (51 to 76 millimeters). The first heating element  62 A is preferably designed to generate and dissipate between about 2 and 7 watts per square inch. 
         [0035]    The first heating blanket  60 A also includes a peripheral region  64 A which lacks the heating element  62 A and which is wrapped around three edges of the first body panel  22 A and secured there by elongate retaining plates or strips  66 A and a plurality of suitable fasteners  68 A or other attachment means which extend through suitable openings in the strips  66 A, the first body panel  22 A and two layers of the first heating blanket  60 A. The inner retaining plate or strip  66 A may either include threaded openings complementary to the fasteners  68 A or may be unthreaded and thus require nuts (not illustrated). 
         [0036]    It will be appreciated that the hinge  30  including the first flange  32 A and the second flange  32 B pivotally connects the first body panel  22 A to the second body panel  22 B. The edges of the air bladder panels  50 A and  50 B are secured to the inside surfaces  28 A and  28 B of the body panels  22 A and  22 B by the silicone adhesive  52  or similar material adjacent the hinge  30 . The longitudinal edges of the heating blankets  60 A and  60 B, including the regions  64 A and  64 B without the heating elements  62 A and  62 B are secured to the respective edges of the first body panel  22 A and the second body panel  22 B with additional elongate plates or strips  66 A and  66 B and the plurality of suitable fasteners  24 . 
         [0037]    Referring now to  FIGS. 5 and 5A , an alternate embodiment of the heating blanket which improves uniformity of heat application is illustrated. The embodiment is the same with regard to the body panels  22 A and  22 B, the hinge  30 , the toggle assemblies  40 , the bladder panels  50 A and  50 B and the elongate plates or strips  66 A and  66 B along the hinge  30 . Each of the heating blankets  72 A and  72 B includes a pair of flexible, spaced-apart panels or electrodes  74  which are co-extensive with and are in intimate electrical contact with an inner resistive layer or element  76 . A thin, preferably electrically insulating outer protective layer or skin  78  may be formed on or disposed over the outside surfaces of the panels or electrodes  74 . The heating blankets  72 A and  72 B provide exceedingly uniform heat and heat application. More importantly, the heating blankets  72 A and  72 B provide heat along their edges or extremities and holes or perforations may be cut or formed in the blankets  72 A and  72 B at any location so long as the panels or electrodes  74  remain separated, i.e., not in electrical contact. 
         [0038]    To ensure this, the fasteners  24 ′ are fabricated of nylon or other rugged, electrically insulating material. It will thus be appreciated that, as illustrated in  FIG. 5 , the edges of the heating blankets  72 A and  72 B may be overlapped slightly to ensure more uniform and improved heat application. It should be understood, however, that the heating blankets  72 A and  72 B are not wrapped around the edges of the first and second semi-cylindrical halves or portions  20 A and  20 B. Rather, they are attached along the edges of the hinge  30  and the rest of the heating blankets  72 A and  72 B float and the remaining edges hang free as this type of heating element cannot be wrapped around an edge as the panels or electrodes  74  are thin but relatively rigid structures. 
         [0039]    Referring now to  FIG. 6 , each of the first and second semi-cylindrical halves or portions  20 A and  20 B of the apparatus  10  also includes an independent air supply assembly  80 A and  80 B. The first air supply assembly  80 A includes a first manifold  82 A having a quick release connector  84 A at one end. The quick release connector  84 A may be coupled to a hose having a complementary connector which is in communication with a source of compressed air (all not illustrated). Additionally and optionally, if it is desired that the apparatus  10  require only electrical power in order to operate, a first small electrically powered air compressor  86 A may be mounted to the exterior surface  26 A of the first body panel  22 A with its output provided to the first manifold  82 A. The first manifold  82 A communicates with the first air chamber  54 A through a suitable fitting  88 A. Also in fluid communication with the first manifold  82 A is a first pressure gauge  90 A. The first pressure gauge  90 A preferably has a range of approximately zero to fifteen or twenty p.s.i. Also in fluid communication with the manifold  82 A is a manually activated pressure release valve  92 A. The pressure release valve  92 A is activated to reduce air pressure or release air within the first air chamber  54 A at the end of a heating cycle or at other times. 
         [0040]    Referring to  FIGS. 1 ,  2 ,  3  and  4 , the second or right semi-cylindrical half or portion  20 B is, as noted above, essentially a mirror image of the first or left semi-cylindrical half or portion  20 A. Thus, it includes an outside surface  26 B having a plurality of braces  34 B including the flat lower portions  36 B, a plurality of stabilizing rods  38 B, an inside surface  28 B, a portion of the toggle clamp assemblies  40 , an air bladder panel  50 B defining a second air chamber  54 B, a heating blanket  60 B having an electrical resistance heating element  62 B as well as retaining plates  66 B and suitable fasteners  68 B. It also includes the second air supply assembly  80 B having a second manifold  82 B, a second quick release connector  84 B, an optional second air compressor  86 B, a second fitting  88 B, a second pressure gauge  90 B and a second pressure relief valve  92 B. 
         [0041]    Referring now to  FIG. 7 , the apparatus  10  includes a single electrical connector assembly  100  which may be secured to the outside surface  26 B of the second body panel  22 B at any convenient location. The electrical connector assembly  100  includes a housing  102  having a pivoting and locking cover  104  which protects a plurality of electrical terminals  106  which are connected to various conductors in a cable  110 . The cable  110  terminates at one or more junctions or feed-throughs  112  where the conductors are connected to the wires of the heating elements  62 A and  62 B or to the electrodes  74 . The conductors in the cable  110  provide electrical energy to the heating blankets  60 A and  60 B (or  72 A and  72 B) and the compressors  86 A and  86 B, if the heat application apparatus  10  is so equipped. 
         [0042]    In operation, the heat application apparatus  10  is opened wider than the position illustrated in  FIG. 2  and placed about a portion of a suspension bridge cable  12  or other cylindrical article. The halves  20 A and  20 B are then closed about the cable  12  or other article and the toggle clamp assemblies  40  engaged and locked. Next, the individual air bladders  54 A and  54 B are filled to an appropriate pressure, preferably between approximately one and five p.s.i. Finally, electrical energy is applied to the heating elements  62 A and  62 B (or  72 A and  72 B) and sufficient heat is applied to the strip or band  16  of cable wrap to cure and/or seal the layers together. The air is then released from the air bladders  54 A and  54 B through the pressure relief valves  92 A and  92 B, the toggle clamp assemblies  40  are released, the apparatus  10  opened and repositioned on the cable  12  or other article. These steps are repeated until the heating and curing or sealing is completed along the length of the cable  12  or other article. 
         [0043]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.