Patent Description:
The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art.

International Publication No. <CIT> describes a moving handrail construction, for escalators, moving walkways and other transportation apparatus with a handrail having a generally C-shaped cross section and defining an internal generally T-shaped slot. The handrail is formed by extrusion and comprises a first layer of thermoplastic material extending around the T-shaped slot. A second layer of thermoplastic material extends around the outside of the first layer and defines the exterior profile of the handrail. A slider layer lines the T-shaped slot and is bonded to the first layer. A stretch inhibitor extends within the first layer. The first layer is formed from a harder thermoplastic than the second layer, and this has been found to give improved properties to the lip and improved drive characteristics on linear drives.

International Publication No. <CIT> describes a method and apparatus for extrusion of an article. A die assembly can apply flows of thermoplastic material to an array of reinforcing cables to form a composite extrusion. A slider fabric can be bonded to one side of the composite extrusion. After exiting the die assembly, the slider fabric can act to support the extrudate as it passes along an elongate mandrel, which can cause the base of the slider fabric to change shape from a flat profile to the final internal profile of the article. The extruded article can then be cooled to solidify the material. The die can include cooling for the slider fabric and means for promoting penetration of the thermoplastic into reinforcing cables.

International Publication No. <CIT> describes modified handrails for use in escalators, moving walkways and other transportation apparatus. Handrail can include a configuration for a cable array as a stretch inhibitor that reduces cable buckling under severe flexing conditions. Handrail can also include a configuration for first and second thermoplastic layers in the lip portions that reduces strain and bending stresses and increases fatigue failure life under cyclic loading conditions. Handrail can also include, for the stretch inhibitor, the use of cables comprising large outer strands and small inner strands that enable penetration and adhesion within the first layer and can reduce incidence of fretting or corrosion.

International Publication No. <CIT> describes a method and apparatus for pretreatment of slider layer for extruded handrails having a slider layer source, a means of conveying the slider layer to a heating module which subjects the slider layer to an elevated temperature for a residence time, and a means of conveying the slider layer to an extrusion die head. One or more control feeders may be implemented for maintaining portions of the slider layer in a substantially tension-free loop as the slider layer is conveyed from the slider layer source to the extrusion die head. A cooling zone may be included to ensure adequate cooling between the heating module and the extrusion die head. Means for reducing heat transfer between the extrusion die head and the slider layer is also provided.

International Publication No. <CIT> describes a handrail that includes a carcass, a stretch inhibitor arranged within the carcass, a cover bonded to the carcass, and a sliding layer secured to the carcass. At a central width axis of the handrail, a face height between an upper exterior surface of the cover and a bottom surface of the sliding layer may be less than about <NUM>. The carcass may be formed of a first thermoplastic material, the cover may be formed of a second thermoplastic material, and the first thermoplastic material may be harder than the second thermoplastic material. The first thermoplastic material may have a modulus at <NUM>% elongation of between <NUM> and <NUM> MPa, and may have a hardness of between <NUM> and <NUM> Shore A.

International Publication No. <CIT> describes a method of and apparatus for extruding an article of uniform cross-section, the article including a thermoplastic material and at least one cable for inhibiting stretch of the article. The cable is supplied to a respective tube and is conveyed between upstream and downstream ends. The thermoplastic material may be supplied to the downstream end of the tube. The thermoplastic material is brought together with the cable to embed the cable within the thermoplastic material, thereby forming a composite extrudate. The tube is configured to at least hinder movement of loose windings of the cable from the downstream end towards the upstream end, which may prevent or at least reduce incidence of "birdcaging". Patent document <CIT> proposes a WPC (wood plastic composite) extrusion profile and a method for its production. An object of the present invention is to provide an improved handrail for use with an escalator, a moving walkway and/or other transportation apparatus.

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 invention, a handrail according to claim <NUM> is provided.

The vapor substance can reduce a density of the at least a portion of the carcass by at least <NUM>% as compared to a density of the polymer matrix. The vapor substance can reduce the density of the at least a portion of the carcass by at least <NUM>% as compared to the density of the polymer matrix. The vapor substance can reduce the density of the at least a portion of the carcass by about <NUM>% as compared to the density of the polymer matrix.

The carcass can have a generally uniform distribution of gas bubbles in the polymer matrix. The gas bubbles can define a generally closed cell structure in the polymer matrix. The gas phase can be formed of particles of a syntactic foam dispersed in the polymer matrix. The particles can include Expancel™ expanded microspheres. The carcass can have approximately <NUM>% (by weight) of the Expancel™ expanded microspheres.

The polymer matrix is formed of a first thermoplastic material. The first thermoplastic material can consist of a polyester-based thermoplastic polyurethane. The first thermoplastic material has a hardness of between about <NUM> and <NUM> Shore A, or can be about <NUM> Shore A.

The carcass can include a first side carcass portion, a second side carcass portion spaced apart from the first side carcass portion, and a central carcass portion of generally uniform thickness extending between the first and second side carcass portions. The central carcass portion can define an upper interior surface, and the first and second side carcass portions can define first and second concave interior surfaces, respectively, adjoining the upper interior surface on either side thereof. The stretch inhibitor can be within the central carcass portion. The sliding layer can be bonded at least to the upper interior surface and the first and second concave interior surfaces.

The handrail can include a cover bonded to the carcass. The cover can include a first side cover portion covering the first side carcass portion, a second side cover portion covering the second side carcass portion, and a central cover portion of generally uniform thickness extending between the first and second side cover portions adjacent to the central carcass portion. The central cover portion can define an upper exterior surface, and the first and second side cover portions can define first and second convex exterior surfaces, respectively, adjoining the upper exterior surface on either side thereof. The first and second side cover portions can further define first and second lower interior surfaces, respectively, adjoined between the first and second concave interior surfaces and generally opposed first and second side interior surfaces, respectively. The cover can be formed of a second thermoplastic material.

The carcass can taper in thickness around the first and second side carcass portions, and the cover can have a corresponding increase in thickness around the first and second side cover portions. The first and second side cover portions can further define the first and second side interior surfaces, respectively.

The cover can taper in thickness around the first and second side cover portions, and the carcass can have a corresponding increase in thickness around the first and second side carcass portions. The first and second side carcass portions can further define the first and second side interior surfaces, respectively. A cover lip height at the first and second side interior surfaces can be between about <NUM> and about <NUM>. Each of the first and second side cover portions can terminate at a position that is offset outwardly in relation to the first and second side interior surfaces, respectively. A cover height at a central width axis can be between about <NUM> and about <NUM>. A cover side width at a central height axis can be between about <NUM> and about <NUM>. The cover can be sized to require between about <NUM> and about <NUM>% of the thermoplastic material of the handrail.

The second thermoplastic material can consist of a polyester-based thermoplastic polyurethane. The second thermoplastic material can have a hardness of between about <NUM> and <NUM> Shore A, or about <NUM> Shore A.

The following is not part of the present invention as defined by the appended claims.

A handrail can include: a carcass; a cover bonded to the carcass; a stretch inhibitor within the carcass; and a sliding layer bonded to the carcass. At least a portion of the carcass can include a gas phase dispersed in a first thermoplastic material.

The carcass can include a first side carcass portion, a second side carcass portion spaced apart from the first side carcass portion, and a central carcass portion of generally uniform thickness extending between the first and second side carcass portions. The central carcass portion can define an upper interior surface, and the first and second side carcass portions can define first and second concave interior surfaces, respectively, adjoining the upper interior surface on either side thereof.

The cover can include a first side cover portion covering the first side carcass portion, a second side cover portion covering the second side carcass portion, and a central cover portion of generally uniform thickness extending between the first and second side cover portions adjacent to the central carcass portion. The central cover portion can define an upper exterior surface, and the first and second side cover portions can define first and second convex exterior surfaces, respectively, adjoining the upper exterior surface on either side thereof. The first and second side cover portions can further define first and second lower interior surfaces, respectively, adjoined between the first and second concave interior surfaces and generally opposed first and second side interior surfaces, respectively. The cover can be formed of a second thermoplastic material.

The stretch inhibitor can be within the central carcass portion. The sliding layer can be bonded at least to the upper interior surface and the first and second concave interior surfaces.

The cover can taper in thickness around the first and second side cover portions, and the carcass can have a corresponding increase in thickness around the first and second side carcass portions. The first and second side carcass portions can further define the first and second side interior surfaces, respectively. A cover lip height at the first and second side interior surfaces can be between about <NUM> and about <NUM>. Each of the first and second side cover portions can terminate at a position that is offset outwardly in relation to the first and second side interior surfaces, respectively. A cover height at a central width axis can between about <NUM> and about <NUM>. A cover side width at a central height axis can be between about <NUM> and about <NUM>. The cover can be sized to require between about <NUM> and about <NUM>% of the thermoplastic material of the handrail.

The gas phase can reduce a density of the at least a portion of the carcass by at least <NUM>% as compared to a density of the first thermoplastic material. The gas phase can reduce the density of the at least a portion of the carcass by at least <NUM>% as compared to the density of the first thermoplastic material. The gas phase can reduce the density of the at least a portion of the carcass by about <NUM>% as compared to the density of the first thermoplastic material.

The carcass can have a generally uniform distribution of gas bubbles in the first thermoplastic material. The gas bubbles can define a generally closed cell structure in the first thermoplastic material. The gas phase can be formed by particles of a syntactic foam dispersed in the first thermoplastic material. The particles can include Expancel™ expanded microspheres. The carcass can have approximately <NUM>% (by weight) of the Expancel™ expanded microspheres.

The first thermoplastic material can consist of a polyester-based thermoplastic polyurethane. The first thermoplastic material can have a hardness of between about <NUM> and <NUM> Shore A, or about <NUM> Shore A.

A method of manufacturing the handrail can include: supplying the stretch inhibitor and the sliding layer to a die assembly; supplying the first thermoplastic material to the die assembly in a molten state; dispersing the gas phase in the first thermoplastic material to form the carcass; bringing the first thermoplastic material together with the stretch inhibitor, thereby to embed the stretch inhibitor within the first thermoplastic material; bringing the sliding layer up against the first thermoplastic material; supplying the second thermoplastic material to the die assembly in a molten state as a separate flow, and bringing the flow of second thermoplastic material up against the first thermoplastic material on an opposing side relative to the sliding layer to form the cover, the first and second thermoplastic materials, the stretch inhibitor and the sliding layer thereby forming a composite extrudate; and extruding the composite extrudate from the die assembly.

The step of dispersing can include introducing a chemical or physical blowing agent to the first thermoplastic material. The step of introducing can include adding particles to the polymer matrix to form a syntactic foam. The particles can include Expancel™ unexpanded microspheres.

A method of extruding an article of constant cross section can include: supplying a first thermoplastic material in a molten state; dispersing a gas phase in a polymer matrix of the first thermoplastic material to form a heterogeneous mixture; and extruding the mixture from a die assembly.

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 invention.

The drawings included herewith are for illustrating various examples of apparatuses and methods of the present invention and are not intended to limit the scope of what is taught in any way. In the drawings:.

Various apparatuses or methods will be described below to provide an example of an embodiment of the claimed invention.

Referring to <FIG>, a handrail is shown generally at reference numeral <NUM>. The handrail <NUM> includes a carcass <NUM>, a stretch inhibitor <NUM>, a cover <NUM>, and a sliding layer <NUM>. The handrail <NUM> can be described as having a generally C-shaped cross section, which defines an internal generally T-shaped slot.

Some current handrails employ a solid, polyester-based thermoplastic polyurethane carcass <NUM> below the cover <NUM>, which is also formed of a polyester-based thermoplastic polyurethane, for encasing and supporting the stretch inhibitor <NUM> from thermo-mechanical damage.

Thermoplastic polyurethane (TPU) is a thermoplastic elastomer consisting of a linear segmented block copolymer composed of hard and soft segments. Introduced by Bayer in <NUM>, TPU was synthesized via a polyaddition reaction of diisocyanates with diols. The polymer's final resin structure is composed of linear polymeric chains of amorphous, flexible soft segments and crystalline, rigid hard segments. The soft blocks enhance the elasticity and flexibility of the polymer. The hard blocks provide the strength and rigidity of the TPU. There are generally no chemical cross-links in the thermoplastic elastomer. The physical cross-links in TPU make it thermally reversible.

TPU can be mainly categorized into three groups based on the composition of the soft segments: polyester based TPUs, polyether-based TPUs, and polycaprolactone TPUs. Polyester-based TPU may provide good abrasion resistance and mechanical properties. Polyether-based TPU may provide low-temperature flexibility and hydrolysis resistance. Polycaprolactone TPUs may have similar toughness and resistance as polyester-based TPUs, but may also feature good low-temperature performance and a relatively high resistance to hydrolysis.

In some examples, the handrail <NUM> may be manufactured using extrusion methods and apparatuses in accordance with the teachings of International Publication Nos. <CIT>, <CIT>, <CIT> and/or <CIT>.

During extrusion, two TPUs (for the carcass <NUM> and the cover <NUM>), steel cords (for the stretch inhibitor <NUM>), and fabric (for the sliding layer <NUM>) may be supplied and extruded through a single die to form the handrail <NUM>. In general, final performance properties of handrails are a combination of each of these component's properties. The carcass <NUM> and the cover <NUM> portions may be formed of different TPU materials with different mechanical properties due to their different roles in the handrail structure.

In some examples, the carcass <NUM> may include a first thermoplastic material, and the cover <NUM> may be formed of a second thermoplastic material. The first thermoplastic material of the carcass <NUM> may be generally stiffer and harder than the second thermoplastic material of the cover <NUM>, and serves to retain a mouth width of the handrail <NUM> to provide a desired lip stiffness. The carcass <NUM> also serves to protect the stretch inhibitor <NUM>, which in this case is formed of the cables <NUM>, and the bond between the cables <NUM> and the first thermoplastic material of the carcass <NUM> may be improved by adhesive (not shown). Although the stretch inhibitor is illustrated to be a plurality of cables, it will be appreciated that the stretch inhibitor can take other forms. For example, a metallic tape or tape including metallic cables embedded in a polymer could be used. In other examples, at least one composite member can be implemented as the stretch inhibitor, which may be formed as a "tape" with a plurality of continuous fibers in a polymeric binder, as disclosed in <CIT>.

The present invention is directed to handrails in which the carcass <NUM> is formed of a reduced density material. The physical properties, chemical resistance, abrasion resistance, good adhesion and ease of processing make TPU a good selection for this application. However, because the cost of TPU tends to be higher than other thermoplastic polymers, there is the potential for increasing the efficiency of material placement on current handrails by reducing the density of the carcass <NUM>.

In some examples, the carcass <NUM> may be formed to be less dense by means of foaming. Foaming is a process whereby a gas phase is introduced into a polymer matrix resulting in cells/bubbles within the material. One of the advantages of foams over solid materials is an improved performance-to-cost ratio. Furthermore, the presence of gas-filled cells not only reduces the mass of material, but it may also provide more cushioning / mechanical damping, which may be desirable depending on the application.

It should be appreciated that, as used herein, the term "gas" is intended to include a vapor substance that is in the gas phase and, in use, is at a temperature that is lower than its critical temperature.

In some examples, it is beneficial to ensure that the cells are uniformly distributed in the matrix structure. This results in weight savings while reducing localized concentration of load and potential for failure. However, foaming is a thermodynamically complex phenomenon and may involve a multi-parametric optimization process for a given material system.

A polymeric foam is a two-phase material where gas is dispersed in a solid polymer matrix. Due to the quick combination of two phases, bubbles or voids are formed and incorporate themselves in the solid matrix. Based on cell morphology, polymeric foams may be categorized as either open cell or closed cell. Open cell foams tend to be more flexible, with cells partially connected by broken cell walls. Closed cell foams tend to be more rigid, with cells separated by complete, well-connected cell walls. The uniformity of polymer-gas mixture depends on the spatial distribution profile of the system's pressure, temperature and gas diffusion in the polymer matrix. Therefore, the system pressure must be greater than the solubility pressure to avoid formation of undissolved gas pockets and to speed up the process. Syntactic foam is a type of polymeric foam and is composed of two components: expandable particles that function as a filler; and a resin system, that functions as a binder. With the addition of filler content in the foam matrix, the system's moduli will be lowered and fracture properties may improve as the filler creates a torturous path for crack propagation.

In some examples, the carcass <NUM> may be formed of a TPU material that is foamed by introducing a foaming/blowing agent into the TPU polymer melt during extrusion, in which there is a heterogeneous mixture of polymer melt and distributed gas bubbles. A uniform dispersion of the blowing agent and an understanding of the rheological behavior of these mixtures may be important for developing and optimizing the processing conditions of a handrail production line.

Expancel™ microspheres have been applied as additives in thermoplastic, coating, paper, and textile industries. The unexpanded microspheres are thermoplastic shells enclosing a droplet of volatile saturated hydrocarbon that vaporizes upon heating. The sphere shells are made of copolymers with different glass transition temperatures. Upon reaching these temperatures, gas pressure from the vaporized hydrocarbons within the spheres cause shell expansion. The microspheres are fabricated through suspension polymerization, which splits the monomer into tiny droplets by mechanical agitation in a liquid phase. The droplets would then be stabilized by surfactants such as silica particles and Mg(OH)<NUM>, preventing agglomeration and coalescence of droplets. The size of the expanded Expancel™ may range from <NUM>-<NUM> and the density may be reduced from <NUM> to <NUM>/m<NUM> upon expansion, which may mostly takes place between <NUM> to <NUM>. When heating up Expancel™, the hydrocarbon evaporates and the gas pressure will soften the thermoplastic shell, leading to expansion of the sphere. The shell will harden, stabilizing and retaining the shape upon cooling. Expancel™ is commercially available in two forms, expanded and unexpanded. The expanded Expancel™ serves as a filler in plastics and elastomers, while the unexpanded is applied as blowing agent in foaming by extrusion and injection molding.

The inventors have investigated making TPU foam using Expancel™ microspheres as a blowing agent in handrail production. Based on experimental results, Expancel™ may be useful as a chemical blowing agent to reduce the density of the carcass <NUM> in the handrail <NUM>, as shown in <FIG>. A suitable Expancel™ content was determined and various properties of the foamed handrail were tested. As described in further detail below, results suggested that various handrail extrusion processing parameters may not need to be changed for manufacturing the handrails including Expancel™ microspheres. The use of a foamed carcass resulted in a reduction of approximately <NUM> wt% in use of the TPU carcass material, and the foamed handrails passed various mechanical tests.

The structure of handrails will now be described in further detail.

Referring again to <FIG>, in the example illustrated, the carcass <NUM> includes a first side carcass portion <NUM>, a second side carcass portion <NUM> spaced apart from the first side carcass portion <NUM>, and a central carcass portion <NUM> of generally uniform thickness extending between the first and second side carcass portions <NUM>, <NUM>. The stretch inhibitor <NUM> is shown arranged within the central carcass portion <NUM>. In the example illustrated, the stretch inhibitor <NUM> is shown formed of a plurality of longitudinal cables <NUM> disposed along a central plane within the central carcass portion <NUM>. The central carcass portion <NUM> delineates an upper interior surface <NUM>. The first and second side carcass portions <NUM>, <NUM> delineate first and second concave interior surfaces <NUM>, <NUM>, respectively. The first and second concave interior surfaces <NUM>, <NUM> adjoin the upper interior surface <NUM> on either side thereof.

In the example illustrated, the cover <NUM> is bonded directly to the carcass <NUM> at an interface to form a continuous body. The cover <NUM> includes a first side cover portion <NUM> covering the first side carcass portion <NUM>, a second side cover portion <NUM> covering the second side carcass portion <NUM>, and a central cover portion <NUM> of generally uniform thickness extending between the first and second side cover portions <NUM>, <NUM>, adjacent to the central carcass portion <NUM>. The central cover portion <NUM> delineates an upper exterior surface <NUM>. The upper exterior surface <NUM> may exhibit a minor convex curve, as illustrated.

In the example illustrated, the first and second side cover portions <NUM>, <NUM> delineate first and second convex exterior surfaces <NUM>, <NUM>, respectively. The first and second convex exterior surfaces <NUM>, <NUM> adjoin the upper exterior surface <NUM> on either side thereof.

In the example illustrated, with the C-shaped cross section, the first and second side carcass portions <NUM>, <NUM> extend around the T-shaped slot and define semi-circular lip portions, which delineate generally opposed first and second side interior surfaces <NUM>, <NUM>, respectively. The first and second side carcass portions <NUM>, <NUM> and the first and second side cover portions <NUM>, <NUM> may each have generally uniform thickness towards the first and second side interior surfaces <NUM>, <NUM>.

In the example illustrated, the first and second side carcass portions <NUM>, <NUM> yet further delineate first and second lower interior surfaces <NUM>, <NUM>. The first lower interior surface <NUM> is shown adjoined between the first concave interior surface <NUM> and the first side interior surface <NUM>, and the second lower interior surface <NUM> is shown adjoined between the second concave interior surface <NUM> and the second side interior surface <NUM>, respectively.

In the example illustrated, the sliding layer <NUM> is bonded or otherwise secured to the upper interior surface <NUM>, the first and second concave interior surfaces <NUM>, <NUM>, the first and second lower interior surfaces <NUM>, <NUM>, and the first and second side interior surfaces <NUM>, <NUM>. The sliding layer <NUM> may include curved ends that are embedded within the cover <NUM> adjacent to the first and second side interior surfaces <NUM>, <NUM>, as illustrated.

Handrails may be manufactured to have varying dimensions, including those in accordance with the teachings of International Publication Nos. <CIT>, <CIT> and/or <CIT>.

The handrail <NUM> shown in <FIG> and <FIG> correspond generally with the teachings of International Publication No. <CIT>.

Various dimensions of the handrail <NUM> are illustrated in <FIG>. It will be appreciated that some of the dimensions mentioned herein refer to just the TPU components of the handrail, the carcass and the cover, while others may refer to the overall structure including the slider layer and/or the stretch inhibitor, which should be clear with reference to the drawings, particularly <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG>.

In the example illustrated, the handrail <NUM> has a face height <NUM> and a side width <NUM>. The face height <NUM> is a vertical dimension at a central width axis <NUM> of the handrail <NUM> between the bottom surface <NUM> of the sliding layer <NUM> and the upper exterior surface <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The side width <NUM> is a horizontal dimension at a central height axis <NUM> of the handrail <NUM> between an inner side surface <NUM> of the sliding layer <NUM> and the second convex exterior surface <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The handrail <NUM> may be generally symmetrical about the central width axis <NUM>, as illustrated, and therefore the side width may be the same on either side of the handrail <NUM>.

Vertical dimensions of the handrail <NUM> further include a handrail height <NUM>, a slot height <NUM>, a lip height <NUM>, a cover height <NUM> and a cover lip height <NUM>. Horizontal dimensions of the handrail <NUM> further include a handrail width <NUM>, a slot width <NUM>, a mouth width <NUM>, a stretch inhibitor width <NUM>, and a cover side width <NUM>.

Dimensions for the handrail <NUM> are provided in Table <NUM>. These dimensions are intended to be illustrative but non-limiting.

In accordance with this example, the cross sectional surface areas of the cover <NUM> and the carcass <NUM> can be approximately <NUM><NUM> (<NUM>%) and <NUM><NUM> (<NUM>%), respectively.

The foaming agent can be applied to handrail designs in a number of ways to reduce the density and cost and improve fabrication. In some examples, the foaming agent can be added to the interior portion of any existing TPU handrail, i.e. the carcass <NUM>. In practice, the inventors have found that significant improvements can be achieved when applying the foaming agent to larger handrails, such as the example shown in <FIG> and <FIG>, which can be supplied as replacements to existing escalators. The relatively large cross section of these products means that more of the TPU material can be foamed.

In the example shown in <FIG> and <FIG>, the carcass <NUM> can be foamed by adding, e.g., <NUM> wt% of Expancel™ <NUM> MB <NUM>. In some examples, the density of the carcass can be reduced by about <NUM>%, which reduces the total TPU required by about <NUM>%.

However, because of the change to the TPU material used for the carcass, the handrail design may require modification in order to maintain satisfactory product performance. Specifically, applying the foaming agent generally reduces the modulus of the TPU material. Handrails achieve their required axial stiffness and dimensional stability in bending from the rigidity of the cross section, and the carcass primarily. In some existing handrails, the carcass can be formed of <NUM> Shore A, Lubrizol Estane <NUM>™, or similar. Adding the foaming agent to this material at a desired amount can reduce the stiffness modulus to a level in which the product could distort excessively in bending and could be prone to derailing from the escalator unit. An alternate TPU carcass material was therefore selected, which had a similar stiffness to Estane <NUM>™ after the addition of <NUM> wt% foaming agent. The material is Covestro Texin <NUM>™ which has a hardness of <NUM> Shore A and similar tensile properties to Estane <NUM>™ after the addition of the foaming agent. Results are shown in Table <NUM> and <FIG>.

A second handrail type where the foaming agent can be applied is in current high-volume products supplied to transit and commercial applications, as taught in International Publication No. <CIT>. Examples are illustrated in <FIG>, <FIG>, <FIG> and <FIG>. In these examples, there is less overall material where the foaming agent can be applied, but the effect can still be significant. The inventors have found that implementing foamed TPU into the carcass in these examples, the TPU requirement can be reduced by more than <NUM>% of the total for the handrail.

Referring to <FIG>, a handrail is shown generally at reference numeral <NUM>. The handrail <NUM> includes a carcass <NUM>, a stretch inhibitor <NUM>, a cover <NUM>, and a sliding layer <NUM>.

In the example illustrated, the carcass <NUM> includes a first side carcass portion <NUM>, a second side carcass portion <NUM> spaced apart from the first side carcass portion <NUM>, and a central carcass portion <NUM> of generally uniform thickness extending between the first and second side carcass portions <NUM>, <NUM>. The stretch inhibitor <NUM> is shown arranged within the central carcass portion <NUM>. In the example illustrated, the stretch inhibitor <NUM> is shown formed of a plurality of longitudinal cables <NUM> disposed along a central plane within the central carcass portion <NUM>. In this example, the carcass <NUM> is shown tapering in thickness around the first and second side carcass portions <NUM>, <NUM>. The central carcass portion <NUM> delineates an upper interior surface <NUM>. The first and second side carcass portions <NUM>, <NUM> delineate first and second concave interior surfaces <NUM>, <NUM>, respectively. The first and second concave interior surfaces <NUM>, <NUM> adjoin the upper interior surface <NUM> on either side thereof.

In the example illustrated, with the C-shaped cross section, the first and second side cover portions <NUM>, <NUM> extend around the T-shaped slot and define semi-circular lip portions, which delineate generally opposed first and second side interior surfaces <NUM>, <NUM>, respectively. The first and second side cover portions <NUM>, <NUM> may each have increasing thickness towards the first and second side interior surfaces <NUM>, <NUM>, respectively, which compensates for the tapering of the carcass <NUM>.

In the example illustrated, the first and second side cover portions <NUM>, <NUM> yet further delineate first and second lower interior surfaces <NUM>, <NUM>. The first lower interior surface <NUM> is shown adjoined between the first concave interior surface <NUM> and the first side interior surface <NUM>, and the second lower interior surface <NUM> is shown adjoined between the second concave interior surface <NUM> and the second side interior surface <NUM>, respectively.

Various dimensions of the handrail <NUM> are illustrated in <FIG>. In the example illustrated, the handrail <NUM> has a face height <NUM> and a side width <NUM>. The face height <NUM> is a vertical dimension at a central width axis <NUM> of the handrail <NUM> between a bottom surface <NUM> of the sliding layer <NUM> and the upper exterior surface <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The side width <NUM> is a horizontal dimension at a central height axis <NUM> of the handrail <NUM> between an inner side surface <NUM> of the sliding layer <NUM> and the second convex exterior surface <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The handrail <NUM> may be generally symmetrical about the central width axis <NUM>, as illustrated, and therefore the side width may be the same on either side of the handrail <NUM>.

Vertical dimensions of the handrail <NUM> further include a handrail height <NUM>, a slot height <NUM>, a lip height <NUM>, a cover height <NUM>, and a cover lip height <NUM>. Horizontal dimensions of the handrail <NUM> further include a handrail width <NUM>, a slot width <NUM>, a mouth width <NUM>, a stretch inhibitor width <NUM>, a cover side width <NUM>.

Referring to <FIG> and <FIG>, the stretch inhibitor <NUM> is shown formed of a plurality of longitudinal cables <NUM> disposed along a central plane within the central carcass portion <NUM>. In the example illustrated, end ones of the cables <NUM> are offset inwardly in relation to the first and second side interior surfaces <NUM>, <NUM>. In other words, the stretch inhibitor width <NUM> is substantially less than the mouth width <NUM>. In operation, having the ones of the cables <NUM> spaced away from regions of stress in the portions <NUM>, <NUM>, <NUM>, <NUM> may affect the ability of the stretch inhibitor <NUM> to retain a neutral plane during flexing.

Referring to <FIG>, a similar handrail is shown generally at reference numeral <NUM>. The handrail <NUM> includes a carcass <NUM>, a stretch inhibitor <NUM>, a cover <NUM>, and a sliding layer <NUM>. The carcass <NUM> is shown tapering in thickness around first and second side carcass portions <NUM>, <NUM>. Compared to the handrail <NUM>, the first and second side carcass portions <NUM>, <NUM> taper more sharply, and first and second side cover portions <NUM>, <NUM> each have a corresponding increase in thickness towards first and second side interior surfaces <NUM>, <NUM>. Otherwise, the structure of the handrail <NUM> is similar to that of the handrail <NUM> shown in <FIG> and <FIG>, and the description of features will not be repeated.

Various dimensions of the handrail <NUM> are illustrated in <FIG>. Dimensions for the handrail <NUM> are provided in Table <NUM>. These dimensions are intended to be illustrative but non-limiting.

The handrails <NUM>, <NUM>, <NUM> with foamed carcasses have each been tested and have been shown to function with satisfactory performance, with specific testing described in further detail below. In addition to cost savings, it has also been shown that there can be advantages in the production process when using the foamed versions of these products.

A further handrail type where the foaming agent can be applied is in a compact handrail design, as taught in International Publication No. <CIT>. Referring to <FIG>, a handrail is shown generally at reference numeral <NUM>. The handrail <NUM> includes a carcass <NUM>, a stretch inhibitor <NUM>, a cover <NUM>, and a sliding layer <NUM>. The structure of the handrail <NUM> is similar to that taught in International Publication No. <CIT>, and the description of features will not be repeated.

The compact construction of the handrail <NUM> may reduce the power required to drive the handrail <NUM>. For example, the handrail <NUM> may be approximately <NUM> to <NUM>% less weight than a traditional handrail product that it is intended to replace. This reduction in weight will translate to lower power consumption on escalators, moving walkways and/or other transportation apparatus.

Similar reduction in TPU requirement can be achieved with implementing foamed materials in this compact handrail design. However, the smaller cross section of the handrail means that modification may be necessary in order to maintain satisfactory product performance. Material selection is one option, but this product may already use a TPU with a hardness of <NUM> Shore A TPU for the carcass. Harder versions of TPU can be difficult to use in the extrusion process and there was a desire to maximize the use of the foaming agent for the greatest possible reduction in density and price. This resulted in the development of new handrail structures, which are shown in <FIG>, <FIG>, <FIG> and <FIG>.

In the example illustrated, the carcass <NUM> includes a first side carcass portion <NUM>, a second side carcass portion <NUM> spaced apart from the first side carcass portion <NUM>, and a central carcass portion <NUM> of generally uniform thickness extending between the first and second side carcass portions <NUM>, <NUM>. The stretch inhibitor <NUM> is shown arranged within the central carcass portion <NUM>. In the example illustrated, the stretch inhibitor <NUM> is shown formed of a plurality of longitudinal cables <NUM> disposed along a central plane within the central carcass portion <NUM>. The central carcass portion <NUM> delineates an upper interior surface <NUM>. The first and second side carcass portions <NUM>, <NUM> delineate first and second concave interior surfaces <NUM>, <NUM>, respectively. The first and second concave interior surfaces <NUM>, <NUM> adjoin the upper interior surface <NUM> on either side thereof.

In the example illustrated, with the C-shaped cross section, the first and second side carcass portions <NUM>, <NUM> extend around the T-shaped slot and define semi-circular lip portions, which delineate generally opposed first and second side interior surfaces <NUM>, <NUM>, respectively.

The first and second side cover portions <NUM>, <NUM> are shown tapering slightly in thickness around the first and second side carcass portions <NUM>, <NUM>. The first and second side carcass portions <NUM>, <NUM> may each have slightly increasing thickness towards the first and second side interior surfaces <NUM>, <NUM>, respectively, which compensates for the tapering of the cover <NUM>.

In the example illustrated, the sliding layer <NUM> is bonded or otherwise secured to the upper interior surface <NUM>, the first and second concave interior surfaces <NUM>, <NUM>, the first and second lower interior surfaces <NUM>, <NUM>, and the first and second side interior surfaces <NUM>, <NUM>. The sliding layer <NUM> may include curved ends that are embedded within the carcass <NUM> adjacent to the first and second side interior surfaces <NUM>, <NUM>, as illustrated.

Various dimensions of the handrail <NUM> are illustrated in <FIG>. In the example illustrated, the handrail <NUM> has a face height <NUM> and a side width <NUM>. The face height <NUM> is a vertical dimension at a central width axis <NUM> of the handrail <NUM> between a bottom surface <NUM> of the sliding layer <NUM> and the upper exterior surface5 <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The side width <NUM> is a horizontal dimension at a central height axis <NUM> of the handrail <NUM> between an inner side surface <NUM> of the sliding layer <NUM> and the second convex exterior surface <NUM> (the surfaces <NUM>, <NUM> are shown in <FIG>). The handrail <NUM> may be generally symmetrical about the central width axis <NUM>, as illustrated, and therefore the side width may be the same on either side of the handrail <NUM>.

In the handrail <NUM>, the cross sectional area of the cover <NUM> is reduced. In some examples, the cover height <NUM> may be between about <NUM> and about <NUM>, the cover side width <NUM> can be between about <NUM> and about <NUM>, and the cover lip height <NUM> can be between about <NUM> and about <NUM>.

In accordance with this example, the cross sectional surface areas of the cover <NUM> and the carcass <NUM> can be approximately <NUM><NUM> (<NUM>%) and <NUM><NUM> (<NUM>%), respectively. The relationship between cross sectional areas of the carcass and cover components can vary. In various examples, the cover can represent between <NUM> and <NUM>% of the overall TPU required for the handrail.

In the handrail <NUM>, the cover <NUM> can be thin, in some examples about <NUM> or less, so that a greater proportion of the handrail <NUM> can be foamed for a greater overall reduction in TPU density. In some examples, the carcass <NUM> can be formed from a TPU with a Shore A hardness of <NUM> to <NUM>, e.g., Texin <NUM>™ with a hardness of <NUM> Shore A. The modulus of the material, and hence the stiffness of the product, can be reduced by the addition of the foaming agent. In some examples, the foaming agent can be added to affect a density reduction of <NUM> to <NUM>%. The cover <NUM> can be formed of the same TPU as used for the carcass, but without the foaming agent.

In such examples, where the cover <NUM> has a higher tensile modulus than the carcass <NUM>, the lip strength, or the ability of the profile to resist opening, will be provided by the cover <NUM> to a larger degree than in the handrails disclosed in International Publication Nos. <CIT> and <CIT>, without the foaming agent. Because of this, as illustrated, the first and second side cover portions <NUM>, <NUM> are shown tapering slightly in thickness around the first and second side carcass portions <NUM>, <NUM>, towards the contact area with the sliding layer <NUM>. This arrangement can prevent the handrail <NUM> from being too stiff in bending.

Alternatively, at density reduction levels of up to approximately <NUM>%, a cover material with lower modulus than that of the base material of the carcass can be used. In one example, Texin <NUM>™ with a hardness of <NUM> Shore A was used as the base material of the carcass <NUM>, and Desmopan <NUM> E™ (Covestro) with a hardness of <NUM> Shore A was used as the material for the cover <NUM>. The density of the carcass <NUM> was reduced by about <NUM>% by using foamed TPU, and the resulting product demonstrated acceptable lip strength and bending characteristics.

Referring to <FIG>, a similar handrail is shown generally at reference numeral <NUM>. The handrail <NUM> includes a carcass <NUM>, a stretch inhibitor <NUM>, a cover <NUM>, and a sliding layer <NUM>. First and second side cover portions <NUM>, <NUM> are shown tapering in thickness around first and second side carcass portions <NUM>, <NUM>. Compared to the handrail <NUM>, the first and second side cover portions <NUM>, <NUM> taper more sharply, and terminate along the first and second side carcass portions <NUM>, <NUM>, respectively. The first and second side cover portions <NUM>, <NUM> each terminate at a position that is offset outwardly in relation to first and second side interior surfaces <NUM>, <NUM>, respectively.

In accordance with this example, the cross sectional surface areas of the cover <NUM> and the carcass <NUM> can be approximately <NUM><NUM> (<NUM>%) and <NUM><NUM> (<NUM>%), respectively. Otherwise, the structure of the handrail <NUM> is similar to that of the handrail <NUM> shown in <FIG> and <FIG>, and the description of features will not be repeated.

In the handrail <NUM>, lip strength and bending characteristics of the product can be optimized by the properties of the components and their configuration. In the example illustrated, to maximize lip stiffness and bending properties, the first and second side cover portions <NUM>, <NUM> are completely tapered off in the lip area.

The production of handrails with foamed materials will now be described in further detail.

Referring to <FIG>, an example of an extrusion apparatus is shown generally at reference numeral <NUM>. The apparatus <NUM> was used by the inventors to conduct experimental production of foamed TPU. The apparatus <NUM> is shown to include a primary hopper <NUM> for storage of dried TPU for the carcass, a vacuum chamber <NUM> coupled to the primary hopper <NUM> for drawing the TPU for the extrusion process, and a side feeder <NUM> for introducing the blowing agent to the TPU. Molten TPU, including the blowing agent, is then fed to a screw extruder <NUM>, which forces the TPU through a series of dies <NUM>, <NUM>, <NUM>. A cooling system <NUM> may be provided, and the apparatus <NUM> may be controlled by an operator via a control panel <NUM>.

TPU for the foam matrix was powderized Texin <NUM>™ TPU, having a hardness of <NUM> Shore A, a specific gravity of <NUM>, and a Tm of <NUM> (Covestro). The foaming agent was Expancel™ <NUM> MB <NUM> with unexpanded microspheres (Akzo Nobel N. ), having a specific gravity of <NUM>-<NUM>/L, particle size ranging from approximately <NUM> to <NUM>. From thermomechanical analysis, the Expancel™ microspheres may reach a maximum volume at approximately <NUM>.

The TPU pellets were dried in the vacuum chamber <NUM> at a pressure less than <NUM> inHg for more than <NUM> hours. The screw extruder <NUM> (e.g., a Harrel Geartruder™ extruder) was positioned with three identical ones of the dies <NUM>, <NUM>, <NUM> attached thereto. During extrusion, a single-phase system is first formed with the matrix and filler in the vicinity of the side feeder <NUM>. At this position, foaming of the TPU is initiated. Downstream, pressure within the screw extruder <NUM> is maintained at a relatively high level. The formation of gas bubbles may affect the shear stress of the mixture. Accordingly, the pressure of the mixture may increase along a die axis as the mixture proceeds towards an entrance of the dies <NUM>, <NUM>, <NUM>.

A barrel temperature of the screw extruder <NUM> was maintained at approximately <NUM> and the expanded TPU was processed with a screw speed of approximately <NUM> rpm. Two temperature profiles at the dies <NUM>, <NUM>, <NUM> were chosen. For a lower temperature setting, the die <NUM> was maintained at approximately <NUM>, the die <NUM> was maintained at approximately <NUM>, and the die <NUM> was maintained at approximately <NUM>. For an elevated temperature setting, the die <NUM> was maintained at approximately <NUM>, the die <NUM> was maintained at approximately <NUM>, and the die <NUM> was maintained at approximately <NUM>. The Expancel™ microspheres were supplied from the side feeder <NUM>, and a weight percentage of the Expancel™ microspheres in the mixture with the TPU was achieved by coordinating supply of materials from the side feeder <NUM> and the primary hopper <NUM>. Foam test strips having diameters ranging from about <NUM> to <NUM> were manufactured and cooled by water at ambient temperature at the cooling system <NUM>.

Referring to <FIG>, an example of an extrusion apparatus is shown at reference numeral <NUM>. The apparatus <NUM> includes a first extruder for the carcass shown at reference numeral <NUM>, and a second extruder for the cover shown at reference numeral <NUM>. Each of the extruders is similar to the apparatus <NUM> described above and shown in <FIG>. The extruder <NUM> includes an inlet <NUM> for carcass TPU and a side feeder <NUM> for the introduction of blowing agent to the carcass TPU. The extruder <NUM> includes an inlet <NUM> for cover TPU and a side feeder <NUM>, which may be used to introduce color concentrate to the cover TPU. Each of the extruders <NUM>, <NUM> are shown to include extruder drives <NUM>, <NUM>, respectively for driving the respective positive displacement pumps. Melt pumps <NUM>, <NUM> and melt pump drives <NUM>, <NUM> are also shown, which are coupled to a melt pump and die cart <NUM>. The TPU for the carcass and cover are fed by the extruders <NUM>, <NUM> to a die assembly <NUM> to manufacture the handrail, e.g., in accordance with the teachings of International Publication No. <CIT>.

The internal structure of a foamed polymer mainly determines its properties, including physical, mechanical, thermal and/or acoustic properties. Therefore, analyzing the morphology of foamed polymers using computed tomography (CT) may be superior to two dimensional imaging techniques as it provides more comprehensive information. The morphology of foamed TPU samples including Expancel™ microspheres formed under various processing conditions were studied using CT scanning (SkyScan <NUM>™, Bruker Corp. <FIG> shows the images of extrusion foamed TPU with approximately <NUM> wt% Expancel™ microspheres. The images show the foamed TPU having a closed-cell structure and cell distribution that is approximately uniform.

From a processing point of view, an understanding of polymer melt viscosity during the foaming process may be important because viscosity may determine whether processing parameters need to be changed as compared with an existing TPU extrusion process. A continuous-flow capillary was employed in-situ on an extrusion line to measure the viscosity of TPU melts with various content of Expancel™ microspheres. The results are shown in <FIG>. By adding <NUM> wt%, <NUM> wt%, <NUM> wt%, and <NUM> wt% Expancel™ microspheres (by weight) to TPU, the viscosity at <NUM> did not show significant change. This suggests that the processing parameters for TPU foaming process may not need to be changed from an existing TPU extrusion process, including, for example, the extrusion methods and apparatuses taught in International Publication Nos. <CIT>, <CIT>, <CIT> and/or <CIT>. However, due to the reduced density of the carcass with foamed materials, there may be minor modifications necessary to an existing TPU extrusion process ensure an appropriate delivery of material to a die assembly. This includes, for example, a reduction in gear speed for a positive displacement pump responsible for supplying the carcass TPU upstream of the die assembly (i.e. the screw extruder <NUM> shown in <FIG>), the reduction corresponding to the resulting reduction in the density of the foamed carcass.

Besides the production process of the foamed handrails, handrail splicing may also be an important consideration because a splice joint may be the weakest part of a given handrail system. In general, there are two kinds of handrail splicing, namely field (at the handrail assembly site) and factory splicing, and these may involve different techniques and structures. Both types of splice joints were prepared using handrails with a foamed carcass. Further details concerning the splicing of handrails may be seen with reference to <CIT>, <CIT> and/or <CIT>.

It was found that the use of a foamed carcass material can result in an easier splicing procedure because of a reduction in spew, requiring less precision to fill the splice mold due to expansion of the foamed material.

Handrails having a carcass of foamed material were evaluated as follows to ensure that they meet mechanical property tests:.

The handrails with a foamed carcass and a field splice joint passed <NUM>,<NUM> hours of outdoor life testing and with factory splice joint <NUM> hours of indoor life testing. This test corresponds to a handrail life of approximately <NUM> years running in the field.

Tensile strength tests were performed on handrail carcass to determine the elongation and tensile stress of foamed carcass TPU. The tested samples were prepared by peeling fabric off the underside of handrail, perform rail cut on a peel cutting machine, and cut to a dumbbell's shape (using a die). Comparisons of elongation and tensile stress of carcass TPU materials are shown in Table <NUM>.

Having good adhesion between the cables of the stretch inhibitor and the carcass may be critical to avoid handrail failure. A standard <NUM>" wire pullout test was performed on a foamed handrail before and after <NUM> hours of indoor fatigue testing, and a fabric peel test was also performed. The results of <NUM>" wire pullout and fabric peel tests are shown in Table <NUM>.

In some examples, the cables of the stretch inhibitor may bear up to almost <NUM>% of the handrail load. The position of the cables within the carcass may be sensitive to the internal stress of the cables. To determine if the addition of Expancel™ blowing agent into the carcass may affect the height and position of the cables, the height of the cables along a cross section of the handrail was measured. As shown in <FIG>, an average height the cables was increased by approximately <NUM>% by adding Expancel™. This suggests that the addition of Expancel™ blowing agent does not lead to a substantial change in the height, but rather the difference may likely be explained by variability between runs.

<FIG> shows cables of the stretch inhibitor positioned within the foamed carcass.

<FIG> and <FIG> show penetration of solid and foamed carcass material, respectively, around one of the multi-strand cables. It appears that the addition of Expancel™ blowing agent may not affect TPU penetration around the cables. The size of the microspheres appears to be larger than the distance between cables, and therefore they are positioned around the group of cables and not in between.

Referring to Table <NUM>, therein is provided an exemplary cost calculation based on handrails produced with <NUM> wt% Expancel™ blowing agent. The calculation is intended to be illustrative and non-limiting. Although <NUM>% of the carcass TPU weight was reduced due to the foamed material, the cost of the Expancel™ blowing agent is approximately four times that of the TPU, and therefore an overall savings of only approximately <NUM>% may be realized. If the proportion of the carcass materials in the handrail is increased, then the potential to save additional cost is increased. In addition to reduced material cost, the use of foamed materials in the carcass may also result in an increase in production speed due to a reduction in the density and heat capacity of the foamed carcass. This results in faster cooling and setup during the extrusion process, which can mean lower production costs.

In summary, by adding <NUM> wt% Expancel™ microspheres, <NUM>% of the carcass TPU cost may be saved, and <NUM>% of the carcass TPU weight may be reduced in a handrail.

Furthermore, although foaming is discussed herein as a particular approach for reducing the density of a handrail carcass, and Expancel™ is named as a particular chemical blowing agent, it may be possible to use other techniques and agents to achieve composite handrails having portions with reduced density and yet acceptable mechanical characteristics. Other chemical blowing agents can be used, such as, for example and not intended to be limiting, Infinergy™ (BASF), or in some cases it may be possible for the foaming to be achieved by mechanically injecting a gas in to an extrusion melt stream.

Moreover, it will be appreciated that terms used herein to convey geometrical or mathematical relationships need not be construed with absolute precision. For example, the terms 'concave' and 'convex' as used herein need not be interpreted to mean structures having a curved surface that is exactly circular. These terms and other terms herein may be interpreted with some flexibility, without strict adherence to mathematical definitions, as will be appreciated by persons skilled in the art. It will also be appreciated that terms used herein to connote orientation, including 'vertical', 'horizontal', 'width' and 'height', correspond to the handrail as illustrated in the drawings and are intended to aid with understanding, but need not refer to the orientation of various components during manufacture and/or use.

Claim 1:
A handrail (<NUM>) suitable for use with an escalator, a moving walkway and/or other transportation apparatus, the handrail (<NUM>) comprising:
a carcass (<NUM>);
a stretch inhibitor (<NUM>) within the carcass (<NUM>); and
a sliding layer (<NUM>) bonded to the carcass (<NUM>),
characterized in that
at least a portion of the carcass (<NUM>) comprises a vapor substance that is in the gas phase dispersed in a solid polymer matrix, and, in use, is at a temperature that is lower than its critical temperature; and
wherein the polymer matrix is formed of a first thermoplastic material having a hardness of between about <NUM> and <NUM> Shore A.