Patent Publication Number: US-2022214297-A1

Title: Insulating element, in particular strip, method of inspection of welds and melting of insulating elements and control system of welds and melting of insulating elements

Description:
TECHNICAL FIELD 
     The invention relates to an insulating element, in particular a waterproofing strip or other insulating parts, by which the control of their connection carried out by melting (melting-down) or welding is important, a method of inspection of welds and melting-down of insulating elements and a control system of welds and melting-down of insulating elements. 
     BACKGROUND ART 
     At present, insulating elements, in particular waterproofing strips, are joined by melting or welding. The quality of these joints is often the basic quality parameter of the insulation to be carried out, since their imperfect execution is often the cause of technical difficulties that cause leakage or even total malfunction of the insulation. Therefore, there is currently a growing demand for an effective and demonstrable inspection of perfect joining of individual insulating elements or perfect adhesion of insulating elements to a substrate. 
     However, such a control system is currently not available. Leakages are more often prevented by organizational measures that lead to more detailed technological procedures and the use of a more qualified operator, but this does not lead to the demonstration of the joint tightness or the adhesion to the entire surface of the substrate. The tightness of welds is checked visually, by an electric spark, by an electric arc, by an ultrasound, by a vacuum bell or by an overpressure exerted in the double-track weld channel. Due to the tensile strength, the overpressure method used in synthetic films cannot be used in some waterproofing systems, for example in asphalt strips. 
     The current inspection methods focus on the tightness evaluation and are usually not able to give information exactly where the faulty connection or adhesion of the insulating element occurred. The existing control possibilities are limited mainly in hard-to-reach places such as corners and passages, where failures of perfect connection or adhesion are most common. 
     The actual tightness of the welds is currently performed visually, by an electric spark, by an electric arc, by an ultrasonic, a vacuum applied bell or by the overpressure exerted in the double-track weld channel. Due to the tensile strength, the overpressure method used in the case of synthetic films cannot be used in some waterproofing systems, for example asphalt strips. 
     Moreover, all the aforementioned methods evaluate only the tightness, not the width of the joint, and are limited by unevenness in the case of vacuum bells, or inaccessibility of corners, or infeasibility for joints of materials with lower tensile strength of the joined material, as in the case of asphalt sheets and overpressure testing. 
     The ultrasonic method is practically impracticable, especially in winter, due to the use of water gels. 
     All methods used so far are laborious, costly and above all inaccurate and unreliable. 
     SUMMARY OF THE INVENTION 
     The invention is based on an insulating element, in particular a strip or other insulating element, joined in particular by melting-down or welding, which is provided on at least one side with a combustible or thermally destructible and electrically conductive element. 
     The electrically conductive element may be a metal foil or a metal fiber. The combustible and electrically conductive element may be attached to the insulating element or the support layer electrostatically, by gluing or by means of a self-adhesive layer. 
     The combustible and electrically conductive element may be a foil having a thickness of 2 to 15 microns, comprising a support layer and a metal continuous or discontinuous layer having a thickness of 1 to 5 microns, or electrically conductive fibers. The metal discontinuous layer may be a system of at least two strips of metal foil having a thickness of 1 to 5 microns, which is applied to the support layer of the combustible and electrically conductive element. 
     The combustible and electrically conductive element may be a film having an inner layer of polyethylene and a metal layer of aluminum or having an inner layer of molded polyester fibers with an admixture of long conductive fibers or having an inner layer of softened polyvinyl chloride with molded electrically conductive fibers or the combustible foil consists of a support layer of polyethylene terephthalate with a conductive metal layer. 
     The combustible and electrically conductive element extends over the entire surface of the insulating element or in a continuous or discontinuous strip at the very edge of the insulating element or is located up to 10 cm from the edge of the insulating element, or anywhere within the entire width of the joint overlap. 
     The present invention also relates to a method of inspecting of welds and melting-down of insulating elements, in particular strips, which is characterized in that the measurement of electrical impedance or electrical capacity detects the presence of a combustible electrically conductive film after thermally bonding the insulating elements, wherein the presence of the electrically conductive film after thermally joining the insulating elements indicates an unburned or insufficiently burnt electrically conductive film and thus poor quality connection of insulating elements. Advantageously, the presence of the electrically conductive layer after the thermal bonding of the insulating elements is converted into an audible signal for an easy indication of imperfect or poorly formed welds or connections of the insulating elements. 
     Another object of the invention is to provide a control system for welding and melting-down of insulating elements, characterized in that it is formed by an insulating element which is provided on one side with a combustible synthetic electrically conductive film for determining the quality of the welds and melting to the substrate and a device for measuring electrical variables for detecting the presence of a combustible synthetic electrically conductive film after thermally joining the insulating elements. The device for detecting the presence of combustible synthetic electrically conductive film after thermally joining the insulating elements is an electrical impedance measuring device or an electrical capacity measuring device. 
     The electrically conductive combustion element is burned down upon melting or welding, in the case of a film including its conductive, for example metallized layer. Due to its conductive layer, the presence or absence of this film is easily identified by its electrical impedance or induction measurement. The presence of an electrically conductive, for example metallized layer, indicates clearly and precisely the points of unburned or insufficiently burnt film, which is a unequivocal and demonstrably evidence of the poor joining of the insulating elements or the adhesion of the insulating element to the substrate. Performing such a proper connection inspection is extremely fast, inexpensive, and provides information on where the incomplete or imperfect connection occurred. At the same time, the operator is usually informed about these imperfections by an audible signal. 
     The invention also makes it possible to detect the residual amount of possibly un-welded film and if the film has not been destroyed at the weld location, this means that a poor-quality weld or melting is carried out at that location, which then needs to be repaired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is shown schematically in the accompanying drawings, wherein 
         FIG. 1  shows the connection of two asphalt strips, wherein the lower asphalt strip is in the mutual overlap provided with the combustible and electrically conductive local film, 
         FIG. 2  shows the connection of two asphalt strips, wherein the upper asphalt strip is provided with a combustible and electrically conductive local film, and 
         FIG. 3  illustrates the joining of the asphalt strips to the substrate where a full-area inspection is required and at least one of the asphalt strips is provided with a fully combustible and electrically conductive film. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The object of the present invention is to provide an insulating element, most commonly a waterproofing strip, at the points where the strips should be joined or where they are to adhere to the substrate, and it is assumed that these are points where the inspection of their joining or adhering by means of the electrically conductive element should be carried out. However, the insulating element can also be a differently shaped insulating element as well as a variety of additional insulating elements, such as roof outlets, passages, grommets and moldings. 
     The combustible and electrically conductive element may be attached to the insulating element or support layer, for example, electrostatically, by gluing or by means of a self-adhesive layer. It can be implemented in an insulating element, in particular a waterproofing strip, directly in the production of the strip, either over the entire surface of the strip or only in a part thereof, at locations in the welded areas. It can also be implemented in the form of a thin self-adhesive foil at the locations of the specified welds directly at the welding site, usually on site. 
     The combustibility of the combustible and electrically conductive element is understood so that as combustible is considered to be the element which is destroyed for example by a flame. For destruction is also understood the destruction of this layer, for example, by hot air or a so-called hot wedge, which utilizes the electrical resistance heating of the steel wedges, followed by an integrated pressure roller. 
     For example, after application of an asphalt strip to the surface, i.e. after laying it and welding by flame or hot air, where the applied temperature must be capable of complete destruction of the combustible film layer including the conductive layer, the quality of welds and local or full-area melting and thus the adhesion to the substrate, are subsequently tested by means of electrical impedance or induction measuring devices which are commonly available. 
     In the case of high-quality welds or melting-down to the base, the film will be destroyed or liquidated, which film will be technologically replaced by a homogeneous joint. The method according to the invention also detects even the residual amount of the un-welded film and if the film has not been destroyed at the weld site, this means that a poor-quality weld or melting has been carried out at that point and needs to be repaired. The most preferred device is a device for measuring the electrical impedance. 
     Example 1 
     In the field of engineering constructions, in particular waterproofing of traffic constructions, bridge decks, tunnels, ditches, reservoirs, dams, dams, leaching areas and reservoirs in mining industry, landfills, water channels, waterproofing of substructures, protection of building structures against ground moisture and water, a bitumen geomembrane or a large-size loose-laid asphalt strip with welded overlaps are advantageously used, where the inspection of welds is generally required. 
     The waterproofing strip is provided with a combustible and electrically conductive film  4 , which consists of an inner layer of polyethylene or polyethylene terephthalate having the thickness 10 microns and a metallic, electrically conductive film, in this case aluminum foil having the thickness 2 microns. In this case, the implementation of the metal foil is carried out directly in the asphalt strip manufacturing plant, but it is also possible to provide this strip with a combustible and electrically conductive element at the construction site, for example by gluing it to the site of the assumed joint design. Locally, it is possible to use a self-adhesive variant of the combustible and electrically conductive film which is applied in details and transversal overlaps either within the production, preparation or on site. The metal foil may also be replaced by another electrically conductive layer, for example by a layer of electrically conductive plastics or an electrically conductive fabric. The combustible metal film can be made discontinuous, that is, it can be made not over the entire surface, but for example in differently spaced strips. 
     As shown in  FIG. 1 , it is necessary to join the lower asphalt strip  1  with the upper asphalt strip  2  by overlapping the two asphalt strips by welding. As a rule, the manufacturer himself specifies the minimum weld width  3  for correct and safe welding. At the edge of the lower asphalt strip  1 , a combustible and electrically conductive foil  4  is placed. 
     The location of the combustible and electrically conductive foil  4  relative to the edge of the lower asphalt strip  1  may vary, in particular according to the quality control requirements of the weld performance. The combustible and electrically conductive film  4  may be positioned on the upper face of the lower asphalt strip  1  overlapping across the inner side of the asphalt strip at a distance from its end edge, preferably about 4 cm from the end edge, and includes only a portion of the required minimum weld width  3  as shown in  FIG. 1   
     Another possibility is to place the combustible and electrically conductive film  4  on the upper face of the lower asphalt strip  1  overlapping across the entire width of the required minimum weld width  3 , usually also at a distance of about 4 cm from the end edge of the lower asphalt strip  1 , taking into account the manufacturer&#39;s requirements for a minimum weld joint width. 
     It is possible to place the combustible and electrically conductive film  4  on the upper face of the lower asphalt strip  1  overlapping over the entire width of the overlap, that is to the end of the edge of the lower asphalt strip  1 . 
     After application of the asphalt strip to the surface and after its welding by flame, where the applied temperature or welding energy is such that the combustion foil including the possible metallized coating is burnt, the quality of welds and full-area melting-down to the substrate including the join homogeneity is subsequently tested by means of the electrical impedance measuring device. 
     Example 2 
     A second specific embodiment is based on the previous example number  1 , but the location of the combustible and electrically conductive film  4  is provided on the lower face of the upper strip in their mutual overlap, as shown in  FIG. 2 . 
     The location of the combustible and electrically conductive film  4  relative to the edge of the upper asphalt strip  2  may vary, in particular according to the quality control requirements of the weld performance. The combustible and electrically conductive film  4  may be disposed on the lower face of the upper asphalt strip  2  overlapping across the inner side of the asphalt strip at a distance from its end edge, preferably about 4 cm from the end edge, and comprises only a portion of the required minimum weld width  3  as shown in  FIG. 2 . 
     Another possibility is to place the combustible and electrically conductive foil  4  on the lower face of the upper asphalt strip  2  overlapping across the entire width of the required minimum weld width  3 , usually also at a distance of about 4 cm from the end edge of the upper asphalt strip  2 . 
     It is possible to place the combustible and electrically conductive film  4  on the lower face of the upper asphalt strip  2  overlapping across the entire width of the overlap, i.e. to the end of the edge of the upper asphalt strip  2 , taking into account the manufacturer&#39;s requirements for a minimum width of the welded joint. 
     Example 3 
     The third specific embodiment of the present invention is based on the requirement that the subject matter of the inspection be a full-surface melting of the insulating element and a full-surface proper adhesion of the insulating element to the substrate. 
     This is particularly advantageous for use in civil engineering, especially waterproofing of traffic constructions, i.e. bridge decks and tunnels, locally reservoirs, barrages, dams, landfills, water channels, where melting to the substructure is required, fully-sealable asphalt strips for waterproofing substructures, for protection of building structures against ground moisture and water, fully-fusible asphalt sheets for roof waterproofing, both single-layer and multi-layer systems and the like. This example of the technical solution is schematically illustrated in  FIG. 3 . 
     This example differs from the previous examples of the particular embodiment of the invention in that at least one of the insulating elements is provided with a combustible and electrically conductive film over the entire surface of the insulating element. 
     In the particular case, it is again the lower asphalt strip  1  and the upper asphalt strip  2 , which in both cases are provided with a combustible and electrically conductive foil  4  over their entire surface, either on the upper or lower surface.  FIG. 3  describes the embodiment, wherein the insulating element, i.e. the lower asphalt strip  2  and the upper asphalt strip  1  are provided with a combustible and electrically conductive film on their lower surface. 
     INDUSTRIAL APPLICABILITY 
     The invention can be used for all kinds of insulating elements, in particular for waterproofing asphalt strips, where the essential aspect for carrying out the insulating works is the need to demonstrably detect the perfect connection of the individual strips of insulation or the perfect adhesion of the insulating element to the substrate. 
     LIST OF REFERENCE NUMERALS 
     
         
           1 —lower asphalt strip 
           2 —upper asphalt strip 
           3 —minimum weld width 
           4 —combustible and electrically conductive film