Patent Application
20120227902
The present disclosure generally relates to elastic and resilient films which are applied to a surface of an endless handrail of an escalator or moving walkway, which can be used to display decorative, informational or other visual material, typically in the form of print applied to one of the layers of the film, that may be used to provide advertising. More particularly, the present disclosure relates to elastic and resilient films for application to a surface of an endless moving handrail, which substantially retard the transmission of materials blooming from the endless moving handrail and affect the appearance of the visual material in the film.
The following paragraphs are intended to introduce the reader to the more detailed description that follows and not to define or limit the claimed subject matter.
According to an aspect of the present disclosure, a method of manufacturing an elastic and resilient film, to be applied to a surface of an endless moving handrail, may include: providing a first layer having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, the first layer including an adhesive on a bottom surface of the first layer, and a barrier coating on a top surface of the first layer, the barrier coating including nano-clay dispersed in an elastomeric material, the elastomeric material being selected from one of neoprene, nitrile rubber, and butyl rubber; providing a second layer having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, the second layer including an adhesive on a bottom surface of the second layer; providing a substantially transparent layer having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, the substantially transparent layer including an adhesive on a bottom surface of the substantially transparent layer; and laminating the first layer, the second layer, and the substantially transparent layer together, wherein the barrier coating substantially retards the transmission of staining chemicals blooming from the surface of the endless moving handrail.
According to an aspect of the present disclosure, a method of manufacturing an elastic and resilient film, to be applied to a surface of an endless moving handrail, may include: providing a first layer having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, the first layer including an adhesive underlying a bottom surface of the first layer, and a barrier coating on at least one of a top surface and the bottom surface of the first layer, the barrier coating including nano-clay dispersed in an elastomeric material, the elastomeric material being selected from one of neoprene, nitrile rubber, and butyl rubber; providing a substantially transparent layer having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, the substantially transparent layer including an adhesive on a bottom surface of the substantially transparent layer; and laminating the first layer and the substantially transparent layer together, wherein the barrier coating substantially retards the transmission of staining chemicals blooming from the surface of the endless moving handrail.
According to an aspect of the present disclosure, a method of manufacturing an elastic and resilient film, to be applied to a surface of an endless moving handrail, may include: providing a first layer including a top surface, a bottom surface, and a barrier coating arranged on at least one of the top and bottom surfaces, the barrier coating including nano-clay dispersed in an elastomeric material, the elastomeric material being selected from one of neoprene, nitrile rubber, and butyl rubber; providing a substantially transparent film layer; and laminating the first layer and the substantially transparent layer together, wherein the first layer, the barrier coating and the substantially transparent layer each have sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail, and wherein the barrier coating substantially retards the transmission of staining chemicals blooming from the surface of the endless moving handrail.
Other aspects and features of the teachings disclosed herein will become apparent, to those ordinarily skilled in the art, upon review of the following description of the specific examples of the present disclosure.
The drawings included herewith are for illustrating various examples of apparatuses and methods of the present disclosure and are not intended to limit the scope of what is taught in any way. In the drawings:
a, 3b, 3c, 3d, 3e, 3f, and 3g show embodiments relating to a flexible and resilient film including three layers;
a, 4b, 4c 4d, 4e, and 4f show embodiments relating to a flexible and resilient film including two layers;
a and 6b are further schematic drawings of the knife-over-roll technique.
Various apparatuses or methods will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover apparatuses and methods that differ from those described below. The claimed inventions are not limited to apparatuses and methods having all of the features of any one apparatus or method described below or to features common to multiple or all of the apparatuses or methods described below. It is possible that an apparatus or method described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or method described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicant(s), inventor(s) and/or owner(s) do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document.
The present disclosure generally relates to elastic and resilient films which are applied to a surface of an endless handrail of an escalator or moving walkway, and can be used to display decorative, informational or other material, typically in the form of print applied to one of the layers of the film. More particularly, the present disclosure relates to elastic and resilient films for application to a surface of an endless moving handrail, which substantially retard the transmission of materials blooming from the endless moving handrail to the film applied to the endless moving handrail. To retard the transmission of these materials blooming from the handrails the present disclosure utilizes one or more barrier coatings.
In the context of the present disclosure, the assignee has developed films which are applied to handrails of escalator or moving walkways. Examples of uses of such films are described in earlier patents, such as for example, U.S. Pat. Nos. 6,450,228, 6,682,806, 7,041,195 7,108,905, and 7,278,528, the contents of each of which are hereby incorporated by reference. The purpose of such films may be either to enhance the appearance of the handrail or to display advertising and other information. Such a film, it is believed, has potential use in a number of applications. For example, it is believed that it may be desirable in high traffic areas such as airports, shopping malls, subway stations etc. Such films may be used to rent advertising space on the surface of the endless moving handrail.
The handrail 1 has a body 300, that may be formed of a variety of materials, as detailed below. The body 300 of handrail 1 defines a T-shaped slot 302. The wires or stretch inhibitors 4 are embedded in the body 300 and may be bonded to the material of the body. The handrail 1 may have shoulders 304 that are generally semi-circular and extend from the top of the handrail around to the underside of the handrail. The shoulders 304 include an upper portion 306 extending through about 90 degrees, starting at a substantially flat portion 3, and an lower portion 308 also extending through about 90 degrees. The upper portion 306 and the lower portion 308 may be separated by a plane that extends through the widest portion of the handrail 1.
At the end of the lower portion 308 there may be a short lip 6. The lips 6, together, have upper surfaces defining the underside of the top section of the T-shaped slot 302. The lips 6 may also have end surfaces facing one another and bottom surfaces, that are, in effect continuations of the outer surfaces of the lower portion 308 of the shoulder 304.
As indicated at 8, film 5 may wrap just a part way around the handrail 1. Alternatively, as indicated at 9, the film may wrap around to a point short of the end surfaces of the lips 6 of the handrail 1 and just before reaching a fabric slider 7, which may extend past the end surfaces of the lips 6.
One of skill in the art will appreciate that in practice the slider is generally embedded into the material of the handrail 1 in the vicinity of the lips 6, and particularly on bottom surface of the lips 6, which are part of the lower portion 308 of the shoulder 304. In
Extension of the film on to the fabric slider 7 is not desirable because the film will only poorly bond to the fabric slider 7 which can result in poor performance of the film. If the film 5 overlies portions of fabric slider 7, the edges of the film 5 in contact with the fabric slider may prematurely separate from the handrail 1, promoting failure of the film 5.
Depending upon a number of factors including the desired appearance, the intended life cycle of the film, and the construction of the film 5 and handrail 1, the extent to which the film 5 wraps around the handrail 1 can be varied. For example, the film 5 can extend to just to cover the substantially flat portion 3 of the handrail 1. Alternatively, the film 5 can extend to wrap completely around the upper portion 306 of the shoulder 304, that is to the widest part of the handrail 1; extend over the upper portion 306 of the shoulder 304 to the neutral axis 310; extend over the upper portion 306, past the neutral axis 310, to a point on the lower portion 308 equidistant from the neutral axis 310 as the substantially flat portion 3 is from the neutral axis 310; extend to cover at least part of the lower portion 308 of the shoulder 304, shown in
It will be appreciated that the further the film 5 wraps around the handrail towards the lips 6, the greater the strain imposed on the film 5 when the handrail flexes. When the film 5 extends around pulleys or rollers while running as part of an escalator or moving walkway, the handrail 1 and portion of the film 5 beneath the neutral axis 310 tend to be put into compression. Such compressive strains tend to promote separation of the edges of the film 5 from the handrail 1, which can lead to puckering of those edges of the film 5.
In some embodiments, the various layers of the film 5 may wrap around the handrail 1 to different extents. Thus, by way of example, one layer may only extend across the substantially flat portion 3, while a second layer may extend to a point 8 or even to 9 just short of the slider 7 and lips 6. As will be described in greater detail below, in some embodiments of the present disclosure, a substantially transparent layer 10 (see, e.g.,
Handrails on escalators and moving walkways are typically made of a variety of materials, including Styrene Butadiene Rubber (SBR), a combination of Styrene Butadiene and Natural Rubber (SBR/NR), Chloro Sulfonated Polyethlene (CSM) or Thermoplastic Polyurethane (TPU), to name a few. A problem associated with the use of advertising films on handrails made from SBR, for example, is that there are various chemicals that bloom onto the handrail's surface which can quickly discolor a decorative film applied thereto. Specifically, many types of rubbers, particularly SBR, incorporate protective materials that over the lifetime of the rubber migrate (bloom) to the surface. These materials act as a protectant for the underlying rubber and help to minimize the deleterious effects of, for example, UV light, ozone, etc. While in many applications these materials are beneficial to rubber, in the context of applying films with a decorative display, these materials blooming out of the handrail can ruin the decorative effect of the film and produce unsightly discoloration.
Some embodiments of the present disclosure utilize a barrier coating (or coatings), as described in greater detail below, applied to one or more layers of the handrail film. This barrier coating retards the progress of materials blooming out of the handrail by creating a tortuous path through which these materials have to pass in order to reach a subsequent layer of the film. This tortuous path effectively increases the amount of time required for these materials to bloom out of the handrail and reach another layer, adhesive, or the print and then affect the visual impact of the film applied to the handrail. At the same time, the layer, upon which the barrier coatings reside should maintain the overall elasticity of the handrail film.
Some embodiments of the present disclosure are particularly directed to preventing the diffusion of materials that will react with either the materials of the films, the adhesives, or the print to visually affect the appearance of the film. Thus, complete prevention of diffusion of material through the barrier coating is not necessary, but rather the barrier coating can be optimized to prevent the diffusion of particular materials that adversely affect the visual impact of the film for a sufficient period of time to allow, for example, an advertisement to be placed for a desired time period.
In another aspect of the present disclosure, the barrier coating is optimized to prevent this diffusion of staining chemicals for a particular period of time. For example, an advertisement applied to a handrail may only be needed for a particular period of time, such as, for example, a one or two days, or a 1-week period for a convention, or alternatively it may be needed for a longer period such as a one, two or three month period during which a particular ad campaign is to be run. The barrier coating can be optimized to retard the diffusion of staining chemicals for a specific period of time.
One of the aspects of the present disclosure is the use of these films as advertising platforms. It is believed that by optimizing the barrier coatings, a business or other owner of a moving handrail can generate recurring and scheduled revenue streams by permitting advertisement on such handrails and also control costs associated with providing that advertising. By tailoring the effectiveness of the barrier coating to the contracted time period, that is ensuring that the barrier coating will be effective for the entire advertising contract period, the business owner can save costs associated with having to remove and reapply an advertisement. Similarly, by tailoring the barrier coating to be effective for no more than the contract period, with proper safety margins, the costs associated with the manufacture of the advertisement itself can be minimized because an advertisement that will only be displayed for a week, does not necessarily require as thick a barrier coating material as one that is to run for a longer period of time such as one or two months. Thus by optimizing the barrier coating material application, the advertising revenue stream can be maximized.
In accordance with some embodiments of the present disclosure, a barrier coating may be formed by dissolving nano-clay in an elastomeric material. Such a nano-clay is available from InMat, Inc., and described in U.S. Pat. Nos. 6,087,016, 6,232,389 and 7,078,453, for example, the contents of which are incorporated by reference. This material is supplied as a liquid form and is applied as a coating.
It has been found that nano-clays, dispersed in an elastomeric material, work well as a barrier. Examples of elastomeric materials include Neoprene, Nitrile rubber, and Butyl rubber. A good dispersion of the nano-clay in the matrix is desired, and the nano-clay should not become clumped together; to the largest extent possible the laminar nano-clay particles should be oriented to be coplanar and in the plane of a film or layer, to enhance their collective barrier effect. It has been found that this product can give a considerably enhanced barrier property, even for a thin layer (e.g., 20 to 25 micrometers (μm) thick after coating/drying). The exact thickness for a particular application will depend on the properties of the materials blooming from the underlying handrail and the duration of time one wishes to retard the migration of these materials. Thus, one of ordinary skill in the art will appreciate that a greater of smaller thickness could be employed without departing from the scope of the present disclosure.
Using these particles, one can enhance the barrier properties of the polymer. At the same time, since the material is based on a number of individual platelets that are not bonded to one another, the polymer retains its elastomeric characteristics.
In some embodiments of the present disclosure (see
a shows a layer 30 upon which the barrier coating is applied. Layer 30 is an elastomeric film having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail. Layer 30 may be comprised of Thermoplastic Polyurethane (TPU). Other materials including Thermoplastic Olefin (TPO), Thermoplastic Elastomers (TPE) such as those sold under the trade name Versaflex® Alloys, Thermoplastic lonomer resins such as that sold under the trade name Surlyn®, metalized TPU, Thermoplastic Vulcanizate (TPV) such as that sold under the trade name Santoprene™, Polyvinylidene Fluoride (PVDF), and Thermoplastic Polyurethane/Polyolefin blends could also be used for layer 30. Among the Thermoplastic Polyurethane/Polyolefin blends are those disclosed in U.S. patent application Ser. No. 11/972,864.
Layer 30 has a top surface and a bottom surface. Adhesive 32 may be applied to the bottom surface of layer 30. Adhesive 32 may be a pressure sensitive adhesive (PSA), or other adhesives as known and used in the art. Examples of appropriate adhesives include acrylic based PSAs, rubber based PSAs, and others. A removable release liner 34 may be applied to adhesive 32 to prevent the adhesive 32 and layer 30 from adhering to themselves or other objects when stored, such as in a rolled condition. Liner 34 may be comprised of paper, linen, polyester or other materials treated for use as a release liner as known in the art. The layer 30 may be between 1.0 and 5.0 mils in thickness and preferably between 1.0 and 3.0 mils. Further, the layer 30 may have a width of between 60 and 170 mm and preferably between 80 and 156 mm.
A barrier coating 36 is applied on at least one of the surfaces of layer 30. In some embodiments of the present disclosure, the barrier coating 36 maybe applied as a single pass of, for example, between 6.0 and 12.0 mils when wet. However, the barrier coating could alternatively be applied in two or more passes, wherein each pass lays down a partial thickness of the barrier coating but resulting in a final barrier layer having the same or a similar thickness as a barrier coating applied in a single pass. It has been found that applying the barrier coating 36 using multiples passes (e.g., between 2 and 4 mils. each when wet), provides a film with improved barrier properties compared to a film with the barrier coating 36 applied in a single pass. In some embodiments, the barrier coating may be, for example, between 3.0 and 16.0 mils when wet, resulting in a dry barrier coating of between 0.3 and 2.1 mils, and preferably between 0.8 and 1.0 mils when dry depending upon the barrier properties needed for the application. The barrier coating can also be applied to both top and bottom surfaces of the layer 30, as shown in
c shows a layer 20, having a top surface and a bottom surface. Layer 20 is preferably white, or another opaque color upon which print can be applied. Layer 20 may be comprised of TPU or other suitably elastomeric materials. Print 26 may be applied to the top surface of layer 20. Print may include words, images or other information that is desired to be displayed. Adhesive 22 may be applied to the bottom surface of layer 20. Examples of appropriate adhesives include PSAs and other adhesives as discussed above. The layer 20 may be between 1.0 and 5.0 mils in thickness and preferably between 1.0 and 3.0 mils. Further, the layer 20 may have a width of between 60 and 170 mm and preferably between 80 and 156 mm. A removable liner 24 may be applied to the bottom surface of the adhesive 22 to prevent the adhesive 22 from causing the layer 20 to adhere to itself or other objects when stored, such as in a rolled condition. Liner 24 may be comprised of the materials discussed above with respect to liner 34.
As used herein the term “print” is used to convey the application of an image, visual material and/or language, possibly repeated at regular intervals along the handrail, to convey a visual or written statement to a viewer. While it is contemplated that this print could indeed be ink such as commonly understood with the term print, the language should not be interpreted so narrowly and should include other methods of conveying such visual statement including, for example, photolithography, and others that might be used in advertising.
The print can be formatted in the film 5 so that in a central portion of the film, the portion that would cover the substantially flat portion 3 of the handrail 1 in
As shown in
In some embodiments, where heat lamination is employed in the method of manufacture, the substantially transparent layer 10 does not include an adhesive 12. In such embodiments, bonding of the substantially transparent layer 10 may be enabled through the heat lamination process itself which is well known in the art.
As used herein the term “lamination” refers to the process whereby multiple layers of film are joined to produce a multi-layer film. This term may include heat lamination, pressure lamination, and other means of joining layers to form the multi-layer film either with or without adhesives.
To form the elastic and resilient film of the present disclosure, these three layers 10, 20, and 30, described above, are laminated together to form a multi-layer film. Liners 14 and 24 applied to layers 10 and 20 are removed, and adhesive layers 12, 22 are bonded to layers 20 and 30, respectively, laminating all three layers together resulting in a three-layer film as shown in
In some embodiments, one or more of the layers 10, 20 and 30 may be laminated to the other layers in the field as the film is being applied to the handrail. Thus for example, the layer 30 could be applied individually to the handrail, and thereafter substantially transparent layer 10 and layer 20 (either individually or commonly if they have been previously laminated together) can be applied to the top surface of layer 30. One of skill in the art will readily appreciate that other orders of lamination of two or more of the layers and the application of the print could be performed without departing from the scope of the present disclosure.
A further aspect of the present disclosure utilizes a reverse print 27, as shown in
In some embodiments of the present disclosure, the adhesive 16 is prepared with a removable liner 14 already applied thereto. The adhesive 16 may be clear, tinted or opaque. The adhesive 16 and the substantially transparent layer 10 are then laminated together after the reverse print 27 is applied to the underside of the substantially transparent layer. The adhesive may be clear, opaque or tinted. Those of skill in the art will appreciate that other adhesives including adhesives not formed on a liner or requiring lamination to the substantially transparent layer may alternatively be used with these embodiments.
Such embodiments lend themselves to laminating with the other layers 20 and 30 in the field, that is at the handrail itself, because, the other layers 20 and 30 are not needed to protect the reverse print 27. Rather, the reverse print 27 is protected by the adhesive 16 and/or a liner 114. Thus, each of layers 10, 20 and 30 could be individually applied to the handrail. Alternatively, layers 20 and 30 can be laminated together prior to application to the handrail, and substantially transparent layer 10 with the reverse print can be applied to these layers after they have been applied to the handrail. Further, all three layers can be laminated together to form a complete film ready to be applied to a handrail in a single application step. Finally, rather than using an adhesive 16, the substantially transparent layer 10 with reverse print applied thereto, may be heat laminated to layer 20, either prior to or after joining layers 20 and 30 to each other.
In some embodiments, the substantially transparent layer 10 may be comprised of a suitable coating, for example a UV-curable clear coating. For example, urethane acrylate formulations and other coatings known to those of skill in the art. In these embodiments, the UV-curable coating, once cured forms a substantially transparent layer 10, but does not necessarily require an adhesive 12 in
Some embodiments may be completely or partially assembled prior to application of the film to a handrail. For example, in some embodiments, layers 20 and 30 may be combined after the print 26 and the UV-cured coating are applied to layer 20. Alternatively, layer 20 and 30 may be joined and thereafter print 26 and the UV-cured coating may be applied. In either event, the result is a film ready to be applied to a handrail. In addition, the joining of the layers may occur in the field as described above. In this alternative, layers 20 and 30 are either individually or jointly applied to the handrail. Where layer 20 already includes print 26 and the UV-cured coating forming substantially transparent layer 10, the layers 20 and 30 are simply joined on the handrail to form a complete film. Alternatively, if layer 20 only has the print 26 applied, and the UV-curable coating is to be applied in the field, the liner covering the print 26 on layer 20 is removed, and the UV curable coating may be applied over the print and the top surface of layer 20. Thereafter a UV-light source may be used to cure the coating. The end result, whether formed as a complete film in a controlled environment or formed in the field appears in cross section as shown in
In some embodiments of the present disclosure (see
a shows a layer 120. Layer 120 is an elastomeric film having sufficient resilience to accommodate strains occurring on the surface of the endless moving handrail. Layer 120 may be comprised of thermoplastic polyurethane or another suitably elastomeric material and have the same width and thickness dimensions as discussed above with respect to layer 20.
A barrier coating 136 may be applied on a bottom surface of layer 120, as shown in
An adhesive 122 may be applied to the bottom surface of the barrier coating 136. Examples of appropriate adhesives include PSAs and other adhesives discussed above. Print 126 may be applied to the top surface of layer 120. A removable liner 124, such as described above, may be applied to the adhesive 122 to prevent the adhesive 122 from causing the layer 120 from adhering to itself or other objects when stored, such as in a rolled condition.
The surface treatments, described above, may enhance the bond of the barrier coating 136 to layer 120, so that when the complete film is removed from a handrail, after its service life, the barrier coating 136 remains adhered to layer 120 and an adhesive 122 remains adhered to the barrier coating 136. Thus a clean removal of the complete film from the handrail surface may be accomplished, which may help to minimize labor costs associated with the film's removal. If the bond of the barrier coating 136 to layer 120 is weak, the barrier coating 136 can separate from layer 120 during removal, and remain adhered to the handrail together with the adhesive 122. This may result in significant additional cost and labor to remove. Though not always necessary, depending upon the formulation of the adhesives and the layers used in the three-layer embodiments described previously, such surface treatments may be employed in those embodiments.
Surface treatments may also be applied to the upper surface of layer 120 to enhance the bonding of the print to layer 120. Such surface treatments may include the use of print-receptive coatings, and/or corona discharge, flame treatment, chemical treatment processes. Again, surface treatments can also be employed in the three-layer embodiments discussed above.
b shows a substantially transparent layer 110. The substantially transparent layer 110 may be used as a protective layer applied over layer 120 and used particularly to protect the print 126 from being damaged. The substantially transparent layer 110, such as described above, is sufficiently resilient to accommodate strains occurring on the surface of the endless moving handrail. Adhesive 112, such as PSAs described above, may be applied to the bottom surface of the substantially transparent film. A removable liner 114, such as described above, may be applied to the bottom surface of the substantially transparent layer 110 to prevent the adhesive 112 from causing the substantially transparent layer 110 from adhering to itself or other objects when stored, such as in a rolled condition. The substantially transparent layer 110 may also be tinted.
In some embodiments, to form an elastic and resilient film suitable for application to an endless moving handrail, these two separate layers, described above, are laminated together. Liner 114 applied to the substantially transparent layer 110 may be removed, and the adhesive 112 along with substantially transparent layer 110 may be applied to layer 120 covering the print 126, thereby laminating the two layers 110 and 120 together resulting in a two-layer film as shown in
In some embodiments, the barrier coating 136 may be provided on the top surface of the layer 120. The top surface of the layer 120 may receive a surface treatment, as described above, to promote adhesion of the barrier coating 136. Further, the barrier coating 136 may also receive a surface treatment to promote adhesion of print thereto. In embodiments where print 126 is to be provided, the print 126 may be applied on a top surface of the barrier coating 136. Alternatively, reverse print 127 may be provided on the bottom surface of the substantially transparent layer 110. The print 126 and the reverse print 127 may include a background color. An adhesive layer 122 may then be provided on the bottom surface of the layer 120. In further embodiments, the barrier coatings may be provided on both top and bottom surfaces of layer 120. An adhesive may be provided on a bottom surface of the barrier coating on the bottom surface of layer 120.
Alternatively, the two layers 110 and 120 can be individually applied directly to a handrail, layer 120 first, followed by the substantially transparent layer 110. This alternative may be particularly useful in embodiments generally as shown in
At a desired time this reverse printed upon substantially transparent layer 110 can be joined to a layer 120 to produce a film as shown in
Further, as described with respect to the three-layer embodiments above, the substantially transparent layer can be a UV-cured coating, as shown in
Another aspect of the present disclosure is that the film may be prestreched prior to lamination and/or prior to application to a handrail, this aspect is also detailed in U.S. Pat. No. 7,278,528. Prestretching of the film can be performed, generally in one direction, and typically of the order of five to twelve percent, e.g., a strain would be applied in the longitudinal direction of the film of the order of five to twelve percent. The exact degree of strain will vary depending upon the film, application, handrail configuration, etc. Nonetheless, such a strain must, necessarily, correspondingly elongate print applied to the film. For many images or patterns, this small percentage of elongation in one direction may not have any significant effect and can possibly be overlooked. For other images, to ensure that the image has desired proportions on the film after application, the image would be, correspondingly, shrunk or reduced in the axial direction, then, when extended, it will be returned to its original, intended length. The axial stretching should have little or no effect on the transverse dimension of an image, although it is known that elongation in one direction can cause a reduction in the corresponding perpendicular dimension, and this can be compensated for where it occurs.
Another aspect of the prestrech is that the degree of prestretch, measured as a strain or percentage elongation of the film, is preferably at least greater than the maximum degree of compressive reduction in length of the film, i.e. negative elongation, that could occur in use, as the moving handrail travels along its path during use. This will then ensure that, all portions of the film, even when the handrail is flexed, will always be maintained in tension. The handrail itself, particularly towards the lips may be subjected to significant compressive strains, but the net strain in the film will always be a tensile strain. Consequently, there should be no tendency for the film to lift from the handrail.
While such prestretching of the film will increase the total tensile load applied to the top portion of the film on top of the handrail, as this is only the relatively short distance from the neutral axis, the total tensile strain applied to the film should still be acceptable. For certain handrail designs, configurations and selection of materials for film, this may result in excessive tensile loads being applied to the film. In such cases, it may be possible to reduce the prestretch applied to the film, so that, for the edges of the film, small, compressive strains may be applied. These should be selected to be so small that they can be readily borne by the adhesive used to adhere the film to handrail without causing any significant wrinkling or puckering to occur.
A variety of techniques can be used to apply the barrier coating to the individual films. One technique is to use roll coating to apply the coating, which are in a liquid form and then a doctor knife or the like to remove excess material.
Such a scheme is shown schematically in
It should be noted that the use of this technique, has the effect of ensuring that the overall thickness of the film and the coating is uniform. This is sometimes referred to as a “post-metered” technique. A post-metered technique can also be effected by using a wire rod or an air knife, or the like.
a through 6d also show schematically the progressive application of a coating using a knife over role technique. This is similar to the technique shown in
a shows this process at the commencement of the coating process. As shown in
Other coating techniques have the effect of ensuring that the thickness of the coating itself is uniform, if there are any irregularities in the thickness of the underlying substrate. Such a technique is referred to as “pre-metered”. In the present case, the underlying substrate is the film layer itself, which is expected to be of substantially constant and uniform thickness. Practically, therefore, it is expected that differences between a post-metered and a pre-metered technique may be slight, but will depend upon the material and quality of the individual film layer.
Pre-metered techniques that provide a uniform coating thickness include among others direct gravure, reverse gravure, offset gravure, reverse roll and slot die. All of these and other techniques such as spray coating, use of slot die coaters to name a few may be applicable for the present disclosure.
While the above description provides examples of one or more processes or apparatuses, it will be appreciated that other processes or apparatuses may be within the scope of the accompanying claims.
This application is a continuation of U.S. application Ser. No. 12/267,158 filed Nov. 7, 2008, which claims the benefit of U.S. Application No. 60/986,868 filed Nov. 9, 2007, each of which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60986868 | Nov 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12267158 | Nov 2008 | US |
| Child | 13478806 | US |
