PROTECTIVE ARTICLE

Abstract: An article for protecting a substrate includes a preshaped member having a shape similar to that of the substrate being protected, the article having a thin layer of gel disposed in inti­ mate contact with an inner surface of the member such that the gel is disposed in intimate contact with the substrate when the member is disposed therearound. Preferably, the gel comprises an open looped three-dimensional network, the gel being rela­ tively soft, elastic, and having an ultimate elongation in excess of 100%.

Description: The present invention relates to an article for protecting a substrate from environmental effects such as corrosion, electrical currents etc. Various ways have been proposed in the prior art for protecting a substrate from adverse environmental effects. For example, in the case of nuts and bolts, in very severe environments such as those encountered on ocean-traversing vessels, multiple layers of paint are often disposed on exposed portions of the nuts and bolts for protecting them from corrosion. As an alternative to paint, various types of greases have also been utilized in many circumstances for protecting substrates from adverse contaminants, such as water, and for electrical insulation protection, and also for insulating metal substrates. These methods are disadvantageous in that insufficient corrosion protection is afforded, reentry is difficult, the protection lasts for a relatively short period of time, they are labour intensive, and relatively expensive. European Patent Publications A-0108518 and A-0174165 disclose various containers which are substantially filled with gel material, the containers subsequently being disposed in contact with a substrate subsequent to curing the gel. Though these gel filled containers are quite effective in protecting substrates, they are disadvantageous in that they are relatively inefficient since a relatively large amount of gel is required per substrate to be protected. EP-A-0108518 discloses an apparatus and method for protection of a substrate, e.g. an electrical contact. The apparatus comprises a support member and an encapsulant which has a cone penetration value of 100 to 350 (10⁻¹m) and an ultimate elongation of at least 200%, and preferably an elastic modulus of less than 10⁷ dynes/cm². The encapsulant and the substrate are pressed together so that the encapsulant is deformed into close and conforming contact with the substrate. Preferably at least a part of the deformation is elastic deformation. The encapsulant, which may be a gel, may be supported by and distributed in a flexible matrix which comprises a plurality of open interstices, the encapsulant comprising a plurality of interconnected segments which lie within the interstices of the matrix. The matrix is preferably in the form of a sheet. Accordingly, it is an object of the invention to eliminate the above-noted drawbacks and to provide an article for protecting a substrate which is relatively inexpensive to produce, is easy to install over the substrate, lasts a relatively long period of time, and can be made easily reenterable, if desired. These and other objects are achieved by articles, and methods of producing such articles, the articles including a preshaped member which has an internal surface shape which is similar to an outer surface shape of the substrate to be protected. In one embodiment, an open surface defined by the preshaped member has a flexible gel disposed thereover, the flexible gel comprising a relatively thin layer of gel, such that when the member is disposed over the substrate, the gel is deformed over and around an outer surface of the substrate and is in intimate contact therewith. A very small amount of gel can be used per substrate to be protected. The gel preferably comprises a three-dimentional open cell network, is elastic, and has finite elongation. Preferably the gel has an ultimate elongation in excess of 200%, more preferably in excess of 400%. Preferably the gel has a cone penetration between 200 and 300 (x 10⁻¹mm). Preferably the layer of gel is less than 10mm thick, more preferably less than 1 mm thick. A gel may be disposed onto a backing, the gel and backing being subsequently deformed using a vacuum thermoforming process whereby the backing and gel are heated, and deformed such that the gel is stretched upon deformation of the backing, the backing being chosen from a material which has sufficient structural strength upon being cooled to keep the gel in its expanded deformed state and in intimate contact with the backing. Suitable materials for the backing include high density polyethylene, kynar and polycarbonate. Subsequent to deforming the backing, a die station is used to separate the deformed backing having gel thereon, which then comprises an article of the invention. According to one preferred embodiment, the gel is disposed onto the backing in a non-cured state, a thickness of the gel is controlled using a doctor blade, the gel is then cured using either chemical means or radiation, the gel is secured to the backing, again using either radiation or chemical means such as adhesive, and subsequently the cured gel and backing are deformed. According to another preferred embodiment of a method of the invention, a pre-cured gel is disposed on the backing, and the pre-cured gel is secured to the backing using either radiation or chemical means prior to deforming the cured gel and backing. Where radiation is used it is preferably beta particle or ultra-violet radiation. The cured gel may have a tacky outer surface. In these cases the method preferably also comprises covering an open side of the deformed backing with a release sheet. Such an article provides an excellent means for protecting irregularly shaped articles using a minimum amount of gel in an efficient manner. Figure 1 is a cross-sectional view of a preferred embodiment of the invention; Figure 2 is a full perspective view of the article of Figure 1 disposed in close proximity to a substrate to be protected, and a partial view of an installed article; Figures 3 - 6 illustrate further embodiments of the invention; Figure 1 illustrates a cross-sectional view of an article 1 constructed according to a preferred embodiment of the invention with Figure 2 illustrating, on the left, a perspective view of the article of Figure 1 in close proximity to a substrate 2 to be protected, and on the right, the article as installed on the substrate. In the embodiment illustrated, the substrate 2 is a bolt 3 having a nut 5 therearound, and the article 1 is generically termed a bolt cover. However, it should be appreciated that the substrate 2 can comprise any kind of element which requires some sort of protection from the environment, such as protection from corrosion, protection from electrical discharge, etc., and that the article 1 comprises any member suitable for protecting such a substrate. The invention is most suitable for use with substrates having irregular shapes, though the invention is also suitable for protecting substrates having uniform shapes as well. Though the invention is described with reference to a few exemplary embodiments, in particular a few specific shaped substrates, it should be understood that the invention is applicable to protecting numerous other types and shapes of substrates as well even though the vast majority of substrates in existence which require some kind of protection are not illustrated in the drawings. The article 1 includes a preshaped member 4 which has an internal surface 6 which has a shape similar to an external surface of the substrate 2 which is to be protected. In particular, the shapes of the surfaces 6, 8 are substantially the same, e.g., most preferably mirror images of one another. The member 4 can be shaped so as to form a tight fit about the substrate 2 when installed, and it is even possible to form the member 4 so as to be slightly smaller in size than the substrate 2 which causes the member 4 to elastically stretch about the substrate when installed providing excellent adhesion. A protective flexible gel 10 is disposed across an open side 12 defined by the shape of the preshaped member 4, and is secured to the preshaped member 4 at a periphery 13 by any appropriate means such as, for example, by an adhesive or by a mechanical clamp. The gel is preferably one of the types described in European Patent Publications A-0108518 and A-0174165. In particular, the gel can comprise a urethane, a silicone, or a nonsilicone liquid rubber with low or no unsaturation which has been crosslinked, with silicone being a preferred embodiment. The gel is a material having an open loop three-dimensional network such that it is elastic and has a finite amount of elongation, and is relatively soft. A preferred embodiment is to use a gel having a cone penetration between 150 and 350 (10⁻¹ mm), and an ultimate elongation of at least 100%, as measured in accordance with American National Standard Designation ASTM-D217 and ASTM-D638, respectively. Preferably, the cone penetration is between 200 and 300 (10⁻¹ mm), and more preferably between 260 and 280 (10⁻¹ mm). A release sheet 9 is disposed over the gel 10, the sheet keeping the gel 10 clean and being releasable therefrom prior to installing the article on the substrate. The ultimate elongation is most preferably in excess of 200%, and most preferably is at least 400%. In addition, as noted, the gel is also elastic such that it tends to resist deformation and generates a restoration force upon being deformed. Furthermore, another preferred embodiment is to contain the gel 10 in a three-dimensional foam network, such as that disclosed in European Patent Publication A-0108518. Specifically, the foam network is characterized by a flexible matrix having a plurality of open interstices having an average volume of less than 0.01 inch³ 0,164 cm³, the gel including a plurality of interconnected segments which lie within the interstices of the matrix, the matrix and the gel being such that when they are stretched, the matrix reaches its ultimate elongation before the gel reaches it ultimate elongation. The thickness of the gel and the matrix need not be large, e.g. it can be less than 10 mm, preferbly less than 5 mm, and more preferably less than 1 mm. One important function of the matrix is to provide tensile and shear strength for the gel. Accordingly, the matrix, though desirable, is not necessary so long as care is taken in sizing the article such that the ultimate elongation of the gel is not exceeded when the article is placed over the substrate. In the case where the gel is made of a polysiloxane material, a suitable adhesive for securing the gel to the member is a silicone pressure sensitive adhesive. In operation, the article 1 as described is disposed over the substrate 2 and placed thereon such that the protective gel 10 is deformed so as to take on a shape roughly illustrated by the dotted line 14 in Figure 1. One embodiment is to provide a small air escape hole to provide a mean for air release from cavity 23 between the number 4 and gel 10 as the cavity 23 contracts in volume upon installation of the article 1. It should be understood that hole 21 is not required. Without the hole 21, air confined within the cavity 23 which contracts upon installation of the article 1 can escape between the periphery 13 of the member 4 and the gel 10 after which the gel, due to its tackiness, re-adheres and seals to the periphery 13. With this construction, atmospheric pressure contributes to maintaining the member 4 in its installed position since removal of the member 4 subsequent to installation requires that the volumne of the cavity 23 be enlarged which results in a pressure decrease in the cavity 23 whereas pressure outside the member 4 and cavity 23 remains constant thereby creating a pressure differential therebetween. Even though the elastic deformation of the gel produces a small force tending to push the article off the substrate, several means are available for preventing this from occurring even if the article is subjected to other external, possibly larger forces, e.g., vibrations. First, if the hole 21 is not provided, as already explained, atmospheric pressure forces would keep the article installed and in place. In addition, the tackiness of the gel also produces a retention force since it is in contact with the substrate and adheres and seals thereto. If the hole 21 is provided, the tackiness of the gel can be made so as to produce sufficient retention forces. In addition, grooves and recesses 16 for engaging threads 17 can be formed on an inner surface of the member 4. If a substrate not having threads is to be protected, it will be apparent to those skilled in the art chat the member 4 may be able to be shaped so as to closely conform in shape to the substrate so as to produce a retention force like that obtained with grooves and recesses which mate with threads, e.g. such as for example grooves and recesses formed on the member 4 which closely conform in shape to similar grooves and recesses on the substrate. Also, the member 4 can be sized so as to form a close fit around at least selected portions of the substrate when installed, and if the material of the member 4 is slightly elastic, it is even possible to size the fit such that the member is caused to stretch around the substrate upon installation which creates relatively large frictional engagement forces therebetween. Any combination of the above is possible when external forces, which may otherwise tend to dislodge the article 1 from the substrate, are anticipated. Accordingly, it can be appreciated that the article 1 can be made to remain in place and to provide good environmental protection means for the substrate 2 such that it is protected from adverse environmental contaminants, such as water or other corrosion-producing substances. In addition if desired, the article 1 is suitable for protecting substrates 2 from electrical currents, eg, the article 1 can have a gel 10 which is electrically insulating. Figures 3-6 illustrate further embodiments of the invention. In Figure 3, the substrate 32 comprises pipes or hoses 32 interconnected by a fitting 33, and the article 34 comprises first and second parts 31, each comprising a pre-formed member 4 and gel 10. The parts 31 are assembled as shown in Figure 4. The tackiness of the gel can be used to keep the parts 31 interconnected, and/or mechanical clamps 36, either integrally formed with the parts 31 or separately attached, can also be used. In Figures 5 and 6, the parts 1 are interconnected on one side by a hinge 35, this embodiment further illustrating the mechanical clamp 36. For more complicated structured substrates, it can be appreciated that any number of the parts 31 in excess of two can be formed so as to be mutually engageable and provide a complete environmental seal for the complicated structured substrate. Though the invention has been described with reference to particular preferred embodiments thereof, it should be appreciated that numerous modifications thereto can be made within the level of skill of the ordinary skilled artisan. For example, the invention is suitable for protecting a wide variety of types of substrates as well as shapes thereof, and is not specifically limited only to bolts, nuts, and pipe fittings, these substrates being described only for illustrative purposes. In addition, by utilizing plural parts 31 as described, it can readily be appreciated that a large degree of freedom is possible in utilizing the invention for protecting a vast array of different types of substrates having various shapes, and the number of preformed members having gel disposed thereon can vary and exceed one or two per substrate when the irregular or unique shape of the substrate makes the use of multiple members in excess of two more practicable. In addition, though several preferred means are described for producing the unique articles of the invention in a continuous manner, it should be appreciated that many variations to the methods described are possible. Accordingly, the invention is not to be limited by the various specific embodiments described, and is to be limited only by the appended claims.

Claims: An article for protecting a substrate, comprising: a first preshaped member having an internal surface shape shaped similar to an outer surface shape of at least part of the substrate to be protected, the member having an open side; and a gel secured to the member for protecting the substrate when the member is disposed over the substrate, the gel being elastic and having a cone penetration between 150 and 350 (10⁻¹mm) and an ultimate elongation in excess of 100%, a volume of the gel being substantially less than a volume enclosed by the internal surface shape and the open side of the member, the gel being cured prior to coming into contact with any part of the substrate, characterized in that the gel is in the form of a thin layer which is secured to the member so as to be disposed across the open side of the member so as to form an open cavity between the gel and the internal surface shape of the member. The article as claimed in Claim 1, an internal surface shape of the preshaped member being substantially a mirror image of at least part of the outer surface shape of the substrate. The article as claimed in Claim 1, the volume enclosed by the internal surface shape and the open side of the preshaped member being slightly smaller than a volume defined by the at least part of the outer surface shape of the substrate. The article as claimed in Claim 1, the volume enclosed by the internal surface shape and the open side of the preshaped member being substantially the same as a volume defined by at least part of the outer surface shape of the substrate. The article as claimed in Claim 1, further comprising means for securing the gel about a perimeter of the pre-shaped member, the securing means being an adhesive or a mechanical clamp, the adhesive being a silicone pressure sensitive adhesive. The article as claimed in claim 1, in combination with a substrate to which it is applied, the preshaped member being disposed around the substrate and being of such a size that it urges the gel into intimate contact with the substrate thereby protecting the substrate. The article as claimed in Claim 1, the gel having a cone penetration between 200 and 300 (10⁻¹mm), having an ultimate elongation in excess of 200%, and being less than 10 mm thick. The article as claimed in Claim 1, the gel being disposed in a flexible matrix, which comprises a material having a plurality of open interstices having an average volume of less than 0.01 inch³ (0,164cm³), the gel including a plurality of interconnected segments which lie within the interstices of the matrix. The article as claimed in Claim 7 or 8, an outer surface of the gel being tacky, and further comprising a release sheet disposed either across the open side of the member and/or in contact with a substantial portion of an upper surface of the gel. The article as claimed in claim 1, further comprising means for keeping the member around the substrate. The article as claimed in Claim 1, further comprising a second preshaped member having an internal surface shape shaped similar to another part of the external surface shape of the substrate and having an open side; a second thin layer of gel, the second layer of gel being disposed either across the open side of the second member or in intimate contact with at least a substantial portion of the internal surface shape of the second member, a volume of the second thin layer of gel being substantially less than a volume enclosed by the internal surface shape and the open side of the second member: and means for securing the first and second members together. The article as claimed in Claim 1, the internal surface shape of the member corresponding to a shape of either an outer surface of a bolt and nut or part of a shape of tube-like members interconnected by a fitting. The article as claimed in Claim 1, the member having a hole through an otherwise closed surface thereof for allowing communication between the cavity and an atmosphere. The article as claimed in Claim 1, the member and thin layer of gel together forming a completely closed surface.

Inventors: DUBROW, ROBERT D., UKEN, WILLIAM DAVID
Applicants: RAYCHEM CORPORATION (A DELAWARE CORPORATION)
Application year: 1986
Main classification: C23F11
IPC codes: H02G15, F16L58, H01R4, B29C63, B29C61, B65D59, B32B1, H01R13, B65D75, H01R43, B32B27, B32B7, G02B6, B29C51