PORTABLE ROADWAY WARNING DEVICE WITH HIGH-DENSITY FILLER AND ABSENT RIGID METAL BALLAST INSERTS

A roadway warning device including a portable rumble strip that includes high-density filler material to achieve a desired overall density and roadway stability of the rumble strip such as for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts. In some embodiments, the filler is dispersed and embedded within a flexible polymer composite matrix of the rumble strip body. In some embodiments, the filler is in the form of discrete unbound pieces of material disposed within a cavity of the rumble strip body. In some embodiments, the filler is in the form of a frangible article disposed within the rumble strip body.

TECHNICAL FIELD

The present invention relates generally to a portable roadway warning device including one or more portable rumble strips to alert an operator of vehicle of an approaching condition, and more particularly to a portable roadway warning device having a portable rumble strip that provides a desired weight and road stability of the rumble strip without the use of conventional rigid metal ballast inserts.

BACKGROUND

Rumble strips are commonly used on roadways to provide a perceptible noise and physical warning vibration to an operator of a vehicle when the vehicle drives over the rumble strip. Rumble strips can be used to slow traffic or warn vehicle operators of an approaching condition, such as a work site, construction site, slow speed zone, checkpoint, and the like, without adversely affecting the stability of the vehicle.

Some types of rumble strips are intended to be permanently installed for long-term use, while others are intended to be temporary and portable for use at work zones and other applications of relatively short duration. Portable or temporary rumble strips generally should be reusable and quick and easy to deploy and remove. They also should have the ability to remain in place under the traffic conditions of their use, preferably without the use of adhesives or fasteners.

Some forms of portable rumble strips fabricated solely of polymeric materials may be suitable for use on roadways at the lower end of the vehicle traffic speed range, such as in parking lots, on residential streets, or the like. These lower-end rumble strips, however, do not have appropriate part density and weight to make them suitable for use at the higher end of the vehicle traffic speed range. Specifically, a lower-end rumble strip made solely of polymeric material typically will have a density below 0.05 pounds per cubic inch (1.38 g/cc), and thus will not produce sufficient pressure on the road surface for acceptable movement stability after encountering impacts from higher speed vehicles.

Rumble strips designed for service on roads and highways at the higher end of the vehicle traffic speed range also may be made with polymeric material, however these higher-end rumble strips often incorporate rigid metal ballast inserts within the polymer material to attain a heavier part density for enabling satisfactory movement stability against the greater impact forces of higher speed vehicles, such as those exceeding 50 miles per hour (80 kph). The rigid metal ballast inserts do not reinforce the physical durability of the base polymeric material of the rumble strip, rather the metal ballast inserts simply add weight to improve stability of the rumble strip during use.

SUMMARY

One problem with higher-end portable rumble strips that incorporate rigid metal ballast inserts is that the metal inserts are prone damage, such as by impact fracture, corrosion, or the like. The metal ballast inserts also typically are in the form of elongated rigid metal bars that can negatively affect the overall flexibility of the rumble strip design.

A unique portable rumble strip for a roadway warning device is described herein that uses high-density filler material to achieve a desired overall density and roadway stability that enables the rumble strip to be suitable for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts.

Generally, a portable rumble strip having an overall part density greater than 0.06 pounds per cubic inch (lb/in3), and more preferably about 0.08 lb/in3or greater, provides acceptable road stability at highway vehicle speeds, such as those in the range of 50 to 80 mph, or greater. Accordingly, an exemplary portable rumble strip has high-density filler(s) dispersed in a polymeric matrix in an amount that achieves an overall part density greater than 0.06 lb/in3, such as in the range from 0.06 lb/in3to 0.15 lb/in3.

According to an aspect, the portable rumble strip has an elongated flexible body that incorporates a composite with a flexible elastomeric matrix having the high-density filler material dispersed therein. The elongated flexible body including the flexible high-density composite may be a single unitary piece. Such a portable rumble strip may provide more complete flexibility in all directions, unlike conventional portable rumble strips that incorporate rigid housings or rigid metal bars into the rumble strip's geometric design. The increased flexibility provided by the elongated flexible body may include a flexible upper surface that absorbs impact from the vehicle, a flexible lower surface that conforms to the roadway surface, and a flexible middle/intermediate portion that facilitates the flexibility of the upper and lower surfaces. Co-vulcanization of distinct layers of the flexible body, if any, may improve overall flexibility and durability of the design.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having a flexible polymeric material matrix and at least one filler dispersed in the matrix that enhances the density of the composite, wherein the at least one filler is included in an amount that provides an overall density of the elongated flexible body in a range from 0.06 lb/in3to 0.15 lb/in3.

In exemplary embodiments, the flexible polymeric material matrix of the composite may be co-vulcanized with the one or more additional portions of the flexible rumble strip body to form a unitary structure.

According to an aspect, the high-density filler material is dispersible and mixable in the polymer matrix material to enable the overall flexibility of the rumble strip body, while also being resistant to corrosion in a typical roadway condition. To enhance the overall density of the part, the high-density filler material has a density that is greater than the density of its surrounding polymeric matrix, and preferably has a specific gravity of at least 3.0 to enable a suitable volumetric loading in the polymeric matrix without significantly affecting the flexibility and performance of the rumble strip design.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having: a flexible elastomeric matrix, and at least one filler dispersed in the matrix, wherein: the at least one filler has a density greater than a density of the flexible elastomeric material matrix; the at least one filler has a specific gravity of 3.0 or greater; and the at least one filler is included in the composite in an amount that enhances the density of the composite, such that an overall density of the elongated flexible body is in a range from 0.06 lb/in3 to 0.15 lb/in3.

In exemplary embodiments, the composite and/or overall flexible body may be devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based filler material that is susceptible to corrosion from road salts.

In exemplary embodiments, the at least one high-density filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element, and more particularly such a material that is resistant to corrosion from road salts.

According to an aspect, the high-density filler material may be useful as a processing aid for the polymeric matrix material. For example, some high-density materials with a specific gravity of at least 3.0 may be used as an antidegradant, accelerator, coupling agent, or the like; and overloading of such a high-density material can be useful to achieve the desired overall part density for improving stability of the rumble strip at higher vehicle speeds.

According to an aspect, a portable rumble strip includes an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, wherein the portable rumble strip includes a composite having a polymeric material matrix and a filler dispersed in the matrix in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix, wherein the density of the filler is greater than a density of the polymeric material matrix.

In exemplary embodiments, the high-density filler includes zinc oxide (ZnO) in an amount between 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix of the composite, in which the ZnO also may be used as a processing aid for one or more polymers in the polymeric material matrix.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein the elongated body includes at least one cavity, and at least one filler in the form of discrete unbound pieces of material is disposed within the cavity.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein one or more frangible articles are disposed in the elongated body.

According to a general aspect, a portable rumble strip for placement on a roadway in a roadway warning system, includes filler material within a body of the rumble strip, the filler material being of a type and in an amount that increases the density of a rumble strip such that its mass can exert a pressure on the roadway to withstand impact from a vehicle, such as a passenger vehicle or heavy truck, without movement of the rumble strip relative to the roadway.

The following description and the annexed drawings set forth certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features according to aspects of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.

DETAILED DESCRIPTION

The principles and aspects according to the present disclosure have particular application to portable rumble strips for high-speed use, and thus will be described below chiefly in this context. It is understood, however, that the principles and aspects according to the present disclosure also may be applicable to other rumble strips for other applications, such as for low-speed applications.

Referring toFIG.1, an exemplary portable roadway warning device10, or system, is shown deployed on a roadway12, such as a highway, to provide a perceptible noise and physical warning vibration to an operator of a vehicle14when the vehicle drives over the warning system10. In the illustrated embodiment, the roadway warning system10includes a plurality of spaced apart portable rumble strips16, each of which is deployed to span across at least a portion of a roadway12. As shown, each rumble strip16of the warning system10may be an independent portable unit, although the warning system10may include rumble strips16operably coupled together, such as end-to-end, which may depend on the length of the rumble strip12and/or the width of the roadway12, for example.

FIG.2shows an enlarged view of an exemplary portable rumble strip16of the warning system10is shown. Generally, the portable rumble strip16has an elongated body18, including an upper or top vehicle engagement surface20and a lower or bottom roadway engagement surface22. Connecting the upper surface20and lower surface22are respective edges, or sides, including a leading edge24for receiving initial impact from the vehicle, an opposite trailing edge26, and lateral side edges27,28that connect the leading and trailing edges24,26. The distance between the upper surface20and the lower surface22generally defines an overall thickness, T, of the rumble strip16, which may correspond to an overall thickness of the edges24,26,27and28. The rumble strip16may have a generally uniform thickness T, or the thickness may vary in the longitudinal and/or lateral directions. As shown, the elongated body18has a length, L, between the lateral side edges27,28that is greater than a width, W, between the leading and trailing edges24,26. In addition, the width W between the upper surface20and the lower surface22is greater than the thickness T of the rumble strip16.

Although the dimensions of the rumble strip16may vary, the elongated body18desirably may be of sufficient length L to reach across a single highway lane, which typically is 11 feet wide, and as such the elongated body18may be in a range from 8 feet to 11 feet in length. The rumble strip16may have its width W in a range between 8 inches and 16 inches. In addition, the rumble strip16should be of sufficient thickness T to generate a noticeable audible and physical vibration to warn the vehicle operator, including truck drivers, when driving over the rumble strip16, but the thickness T should not be so severe as to startle the drivers, and should not cause damage or adversely affect the stability of the vehicles. To that end, the exemplary rumble strip16may have its thickness T in a range between 0.5 inch and 1 inch, and more preferably may be about 0.75 inches, for example.

To facilitate ease of portability and enable the rumble strip16to be picked up and transported by hand, the elongated body18of the portable rumble strip16may include one or grips30. As shown in the enlarged view ofFIG.3, for example, the grips30may be in the form of hand grip slots. The grips30may be adjacent to one or both lateral side edges27,28of the rumble strip body18, as shown. Although not shown in the illustrated embodiment, one or both of the lateral side edges27,28of the elongated body may include a suitable connector for connecting the rumble strip16to another rumble strip of the portable warning system10. This may be particularly desirable where the roadway is wide, or the overall length L of the rumble strip16is less than 8 feet.

In exemplary embodiments, the elongated body18of the rumble strip16has sufficient flexibility to permit the rumble strip16to be rolled up lengthwise from one lateral side edge27to the other lateral side edge28(end-to-end) for ease of transportation and storage when not in use, and just as easily unrolled during deployment of the rumble strip16. Such rolling may include simply folding or bending the rumble strip16essentially in half so that the lateral side edges27and28are brought closer together, or may include rolling the rumble strip16in a spiral pattern, as shown inFIG.3for example. When rolled into a spiral roll, the rumble strip16may have an outer diameter between about 18 inches and 48 inches, for example.

To achieve such flexibility, the elongated flexible body18of the rumble strip16is made with a base material of one or more suitably resilient or flexible materials. Such resilient or flexible materials may include one or more suitable types of polymer, such as suitable elastomeric materials, including by way of non-limiting example: natural rubber, ethylene propylene diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), butyl-rubber, nitrile-rubber, or other thermoset or thermoplastic elastomers, such as polyurethane, including any combinations of the foregoing.

Because the flexible material(s) of the type(s) described above generally have a density of about 0.04 lb/in3to about 0.05 lb/in3the flexible material(s) of the rumble strip body18on their own do not provide sufficient pressure on the roadway surface to remain in place under heavy traffic at higher end highway speeds. Accordingly, the exemplary portable rumble strip16described herein uses high-density filler material within a flexible material matrix of the rumble strip body18to achieve a desired overall part density that enables the rumble strip16to be suitable for use in high-speed traffic conditions, while also providing enhanced freedom of flexibility in multiple directions to aid in performance and portability of the rumble strip design.

Referring to the lateral cross-sectional view ofFIG.5and the longitudinal cross-sectional view ofFIG.6, one exemplary form of the flexible rumble strip body18made with a high-density composite32having a flexible material matrix34and at least one high-density filler material36dispersed in the matrix34is shown. As described in further detail below, the amount and combined weight of the high-density filler material36dispersed in the flexible material matrix34should be sufficient to cause the rumble strip16to stay in place under heavy traffic at highway speeds, but should not make the rumble strip16so heavy that it cannot easily be rolled up or moved by one or two persons. For example, the overall weight of the rumble strip body18approximately 11 feet in length by about 1 foot wide by about 0.75 inch thick may be in a range from about 75 lbs. to about 125 lbs., such as about 100 lbs. In addition, the high-density filler material36preferably is dispersed within the flexible material matrix34in a manner that provides enhanced freedom of flexibility of the rumble strip body18in multiple directions to thereby aid in the performance, conformability to the road surface, portability, or storability of the rumble strip.

As shown in the lateral cross-sectional view ofFIG.5, the high-density composite32having the flexible material matrix34and high-density filler36may constitute essentially the entirety of an upper portion38of the flexible rumble strip body18, including the upper vehicle engagement surface20, an intermediate (e.g., middle or center) portion40between the upper surface20and lower surface22, and a majority of the respective edges24,26,27and28. As shown in the longitudinal cross-sectional view ofFIG.6, the high-density composite32forms a portion of the rumble strip body18in the longitudinal direction, which may be along a majority of the rumble strip length, or essentially an entirety of the rumble strip length. In exemplary embodiments, one or more additional portions or layers of flexible material may be provided in the rumble strip body18, such as a lower or bottom portion42that includes the lower surface22. As described in further detail below, the lower portion or layer42may be formed with a different flexible material composition than that of the upper portion38having the high-density filler36(also referred to as the upper composite layer38or high-density composite layer38in this embodiment).

As shown in the cross-sectional view, the upper vehicle engagement surface20, the lower roadway engagement surface22, the trailing edge26, and the lateral side edges27and28, each may be substantially flat surfaces, with the trailing edge26and side edges27,28being perpendicular to the upper and lower surfaces20,22. The leading edge24of the rumble strip body18that faces toward oncoming vehicle traffic may be tapered or beveled to reduce any possible movement of the rumble strip caused by initial contact of the vehicle tires with the rumble strip. The included angle of the tapered or beveled leading edge24may be in the range from about 10-degrees to about 15-degrees, for example. The shape and dimensions of any of these surfaces20,22,24,26and28may be modified as desired to achieve certain functionality of the rumble strip16. For example, the upper vehicle engagement surface20may be cambered or rounded in the width direction between the leading and trailing edges24,26. Likewise, the trailing edge26could be tapered or beveled similarly to the leading edge24.

To provide a better grip between the lower surface22and the roadway, or to reduce possible skidding of vehicle tires against the upper surface20, one or both of the upper and lower surfaces20,22of the rumble strip body18may have texturing44. The texturing44may be in any suitable form, such as in the form of an open diamond pattern (as best shown inFIG.4) to provide a channel effect to permit the escape of water from both underneath and above the rumble strip16.

As noted above, the lower portion or layer42of the flexible rumble strip body18may be formed with a different flexible material composition than that of the upper high-density composite layer38having the high-density filler36. The flexible material composition of the lower layer42may be made of any suitable flexible material composition, which may or may not be a composite having additional filler material contained within a flexible material matrix of the lower layer42.

To further increase the grip between the lower surface22of the rumble strip and the roadway, the lower layer42of the rumble strip body may be made with a softer polymer material than the flexible matrix material34of the upper layer38. For example, the lower layer42of the rumble strip body18may have a Shore A hardness in a range from about 40 to about 60, such as about 45; and the upper high-density composite layer38may have a Shore A hardness in a range from about 65 to about 80, such as about 75. This may enable the lower layer42to better conform to an uneven roadway surface to enhance contact area, while enabling the upper layer38to better withstand highspeed vehicle impact. It is understood, however, that these relative hardnesses between layers38,42(or any other layers) may be the same, or may be varied as desired.

Because the upper portion38and/or intermediate portion40of the rumble strip body18may contain the high-density filler36while the bottom portion42does not, the thickness or volume of the high-density composite32(i.e., upper composite layer38in the illustrated embodiment) may be several times greater than the thickness or volume of the lower portion42. For example, where the overall thickness T of the rumble strip body18is approximately 0.75 inches, the thickness T1of the upper portion38may be approximately ⅝ inch and the thickness T2of the lower portion42may be approximately ⅛ inch, for example. This can enable the lower portion42to provide functional conformance and damping, for example, without providing too much material that is absent the high-density filler36, which could otherwise affect the overall (average) part density and thus roadway stability.

In exemplary embodiments, the upper high-density composite layer38is integrally formed with the flexible material of the lower layer42(or other layers, if any), such as via co-vulcanizing of the layers, thereby forming a unitary flexible body18of the rumble strip. In such a co-vulcanizing process, the respective flexible materials (e.g., elastomeric polymers) of both the upper layer38and lower layer42are heated and cured such that the polymeric chains of both layers38,42are crosslinked together to form a unitary structure. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. In the illustrated embodiment, for example, due to crosslinking of the flexible material(s) between layers38and42, including the flexible material(s) of the composite32, the overall rumble strip body18is considered to be a single unitary body.

Although the layers38and42(and/or other layers, if any) may be integrally formed into a unitary structure as noted above, alternative processing techniques for forming the flexible body18also may be employed. For example, alternatively or additionally to co-vulcanizing and/or co-molding, the heated viscous material of one or both layers38,42(or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions38or42could be preformed and precured as a discrete article, and the other layer portion(s)38or42could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions38,42(or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive, such as an adhesive that provides porous wicking and/or crosslinking (after heating/curing) with one or both of the upper and lower portions38,42. Although these alternative processing techniques may be employed, it may be preferred that multiple layers of the flexible body18(e.g., upper and lower layers38,42including composite32), if any, are formed as integral and unitary with each other such as by co-vulcanization/crosslinking. This can improve the durability of the rumble strip design by reducing and eliminating interfaces between layers, and also can improve the overall flexibility of the rumble strip design. It is furthermore understood that although the upper and lower portions38,42are shown as distinct layers of different material, the entirety of the rumble strip body18could be fabricated with the flexible high-density composite32having the high-density filler36contained within.

As indicated above, the high-density composite32of the rumble strip body includes a flexible material matrix34and at least one high-density filler material36dispersed in the matrix34. The high-density composite32also may include other materials to aid in the performance of the rumble strip or to aid in the fabrication of the rumble strip, as may desired. For example, the high-density composite32may include minor constituent materials used to aid in the processing of the polymeric (e.g., elastomeric) material, such as processing aids, curatives, or other constituent materials. These various ingredients of the exemplary composite composition (also referred to as a “compound”) will be described in further detail below.

Flexible Material Matrix

The flexible material matrix34of the high-density composite32may include any suitable polymeric material or combination of polymeric materials that provides a desired flexibility of the rumble strip body18, and also which enables a desired distribution of the high-density filler material36within the flexible material matrix34. By way of non-limiting example, the flexible material of the matrix34may include suitable elastomers, including natural rubber, ethylene propylene diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), butyl-rubber, nitrile-rubber, or other thermoset or thermoplastic elastomers, such as polyurethane, or the like, including any combinations of the foregoing. In exemplary embodiments, one or more or all of the polymeric matrix materials are cured (vulcanized) to form a crosslinked polymeric matrix. The density of only the flexible polymer material portion(s) of the rumble strip body18(without accounting for the high-density filler36or other materials) generally is in the range from 0.035 lb/in3to 0.050 lb/in3.

Processing Aids, Curatives, and Other Constituent Materials

The high-density composite32(e.g., upper composite layer38) and other polymeric portions of the rumble strip body (e.g., lower layer42), if any, may include other constituent materials, or remnant traces thereof, including processing aids, curatives, or other minor constituent materials used to aid in the processing of the polymeric (e.g., elastomeric) material. For example, without limitation, during compounding of the high-density composite32, the polymeric compound of the flexible matrix material34may include, in addition to elastomer(s), the following additional ingredients (with exemplary amounts in parts by weight per hundred polymer (e.g., elastomer) where “hundred polymer” (e.g., “hundred elastomer”) as used herein means 100 parts by weight total polymer(s) (e.g., total elastomer(s)): processing oils/aids (from about 0 to about 75 phr), antidegradants (from about 0 to about 10 phr), curatives (from about 0 to 10 phr), accelerators (from about 0 to about 10 phr), coupling agents (from about 0 to about 30 phr), colorants, and the like. These ingredients or other suitable ingredients may be added as noted, increased, decreased, or omitted, as may be desired to achieve the desired propert(ies) of the flexible material matrix34.

It has been found that the portable rumble strip body18having an overall body density greater than 0.06 lb/in3, and more preferably about 0.08 lbs/in3or greater, provides acceptable road stability at highway vehicle speeds. As noted above, the density of only the flexible polymer material portion(s) of the rumble strip body18(without accounting for the high-density filler36or other materials) generally is in the range from 0.035 lb/in3to 0.050 lb/in3, which falls which below the desired overall rumble strip body density.

Accordingly, the exemplary rumble strip16provides the high-density filler material36dispersed in the flexible material matrix34of the rumble strip body in an amount that achieves an overall part density greater than 0.06 lb/in3, and more preferably at least about 0.08 lb/in3or greater, such as an overall part density in the range from 0.06 lb/in3to 0.15 lb/in3. This increased density of the rumble strip body18restricts movement of the portable rumble strip by vehicle impact, or raising up from the roadway caused by the trailing draft of passing vehicles. In exemplary embodiments, this increased overall part density is achieved without the use of rigid metal ballast inserts such as solid metal bars molded into the flexible body18or attached to the body. As used herein, the term “overall part density” or “overall body density” refers to an overall density of the entire elongated flexible body18of the rumble strip16; whereas the phrase “composite material density” or “layer density” refers to an overall or aggregate density of that particular layer or composite portion of the body18.

The high-density filler material36(also referred to as high-density filler36) may be any suitable material (or combination of materials) in any suitable form (or combination of forms) that is mechanically mixable, dispersible, and fixable within the flexible material matrix34prior to permanently forming the high-density composite32of the rumble strip body18. This is in contrast with conventional rigid metal ballast inserts, like metal bars or other large pieces of metal such as those greater than 10 mm in length (e.g., metal slugs, or the like), which cannot practically be mixed and dispersed within the flexible material matrix34, but instead are inserted and then molded in place. The distribution of the high-density filler36in the flexible material matrix34may be achieved by any suitable technique, such as via conventional elastomeric mixing techniques (e.g. internal mixers, mills or extruders) and conventional molding techniques (e.g., compression molding and vulcanizing, transfer and injection molding, or the like).

As indicated above, the high-density filler material36is dispersed within the flexible material matrix34in a manner that provides enhanced freedom of flexibility of the rumble strip body18. This enhanced freedom of flexibility may include flexibility in multiple directions of the rumble strip body18, such as in two or more of the x-(lateral), y-(longitudinal) and z-(vertical) directions (illustrated inFIG.2). For example, the enhanced flexibility of the rumble strip body18may include flexibility and resiliency of the upper vehicle engagement surface20that absorbs impact from the vehicle. The flexible body18should possess acceptable physical durability to withstand the continuous impacting forces from heavy vehicle traffic, including that of semi-trucks for example. In addition, the lower roadway engagement surface22may have sufficient flexibility such that it can conform to an uneven roadway surface or crown. The increased contact area provided by such a lower flexible surface22enhances the resistance to sliding or movement during impact from moving vehicles. Furthermore, an intermediate portion40, or middle, of the flexible body18also has sufficient flexibility to enable the flexible movement of the upper and lower surfaces20,22of the body. The flexible intermediate portion40also may provide a greater degree of flexibility to enable rolling of the portable rumble strip16(as shown inFIG.3, for example) to aid in the portable deployment, removal, or storage thereof.

In exemplary embodiments, the high-density filler material36is uniformly dispersed throughout the flexible material matrix34such that the overall composite32has uniform properties, including that of hardness, flexibility, strength, and the like. This is in contrast with conventional rigid metal ballast inserts (such as solid metal bars) that are not dispersed within the matrix, but rather are typically inserted or molded in place at localized regions of the body, which thereby results in less flexibility of the body. Generally, the larger the size of the high-density filler material36, the more difficult it is to mix and uniformly disperse, and thus the less uniform are the properties of the overall composite, which may affect overall flexibility.

The high-density filler36may be in any suitable form, such as powder, particulate, fragments, grains, pellets, balls, short fibers, or the like, which may be in any suitable size or shape, such as round, blocky, elongated, acicular, or the like. A typical size of the individual pieces of high-density filler material36may be in a range from about 0.1 micrometers (microns) to about 1 micron, for example; however, the size could be in a range from below about 0.1 microns to about 500 microns. Generally, if the size of the high-density filler36is too large and heavy, it can affect processability and uniform distribution of the high-density filler36in the flexible material matrix34. In exemplary embodiments, the size of the high-density filler material36has a mean size (D50) in a range from about 0.1 microns to about 1,000 microns, and more particularly in a range from about 0.1 microns to about 500 microns, and even more particularly in a range from about 0.1 micron to about 100 microns, for example.

As noted above, the high-density filler material36is provided to increase the overall part density of the rumble strip body18, and thus the high-density filler material36has a density that is greater than that of its surrounding flexible material matrix34. Also noted above, in exemplary embodiments the high-density filler36is loaded in an amount that achieves an overall density of the rumble strip body18in the range from about 0.06 lb/in3to about 0.15 lb/in3, or more preferably at least about 0.08 lb/in3. The amount of high-density filler material36(in both weight and volume percent) in the composite32will vary based on the density (specific gravity) of the high-density filler material36(or combination of high-density materials). For example, Table 1 shows four exemplary compositions in accordance with specific embodiments which show an amount by weight of high-density filler material36, and other ingredients, in parts per hundred (phr) by weight total elastomer(s) of the flexible material matrix34.

Although only four different types of high-density filler36are shown in Examples 1-4 of Table 1, the exemplary composition of the high-density composite32is not limited these specific types. Generally, exemplary types of the high-density filler material36may include, but is not limited to, oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements. Examples of such metal elements forming the oxides, carbides, sulfates, etc., of the high-density filler include, but are not limited to, calcium, barium, magnesium, iron, zinc, and lead, among others. Some types of these materials will be better suited based on environmental conditions (e.g., corrosion-resistance), processability with the polymeric or elastomeric matrix34, or cost, among other considerations, as discussed in further detail below.

Generally, the amount and density of the high-density filler material36is sufficient to achieve the desired overall part density of the rumble strip body18, while also enabling suitable volumetric loading of the high-density filler36in the flexible material matrix34without significantly affecting the flexibility and performance of the rumble strip design. As is evident from the Examples in Table 1, the amount by weight of high-density filler material36in the composite will vary based on the density (specific gravity) of the high-density filler material (or combination of materials) because this will affect the volumetric ratio of high-density filler to flexible matrix material34. Because the elastomer(s) of the flexible material matrix34have a density of about 0.04 lb/in3to about 0.05 lb/in3, and because the desired overall density of the rumble strip body18is preferably about 0.08 lb/in3or greater to achieve the desired weight and road stability for highway vehicle speeds, it has been found that using fillers with a specific gravity below 3.0 makes it difficult to attain the other desired properties (e.g., flexibility, strength, etc.) of the flexible body18. This is because a filler material with a specific gravity below about 3.0 may require too much to be added to attain a targeted material density of at least 0.08 lb/in3, and as the filler loading increases, the desired properties of the composite (compression set, permanent set, elongation, flexibility, etc.) decrease. Thus, a specific gravity of the high-density filler36(or average specific gravity of the combination of materials in the filler36) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example.

By way of comparative example, if the 250 parts of lead oxide (PbO) in Example 1 were replaced with talc (magnesium silicate), then this would require 1500 parts to achieve the same 0.09 lb/in3density, and this amount of talc would not result in a suitable compound. This is because talc has a specific gravity of 2.6 and lead oxide (litharge) has a specific gravity of 9.5. Generally, based on a specific gravity of the high-density filler being at least about 3.0, an exemplary amount of the high-density filler36(or combination of high-density fillers) in the composite composition may be in a range from about 100 phr to about 1100 phr (parts by weight per 100 parts by weight of total polymer(s) (e.g., total elastomer(s)) of the flexible polymer matrix34), such as about any of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or 1100 phr, which may be based on the specific gravity of the high-density filler(s)36.

Because the high-density composite32of the rumble strip body18may constitute only a portion of the overall rumble strip body18, the high-density composite portion (i.e., upper composite layer38in the illustrated embodiment) may require a density greater than 0.08 lb/in3to compensate for the relative lower density of the other part(s) of the body (e.g., lower portion42in the illustrated embodiment). Accordingly, based on the volume of the high-density composite32in the rumble strip body18relative to other portions, the high-density composite portion may have a density in a range from 0.08 lb/in3to 0.15 lb/in3, and more preferably in a range from 0.09 lb/in3to 0.15 lb/in3, such as about any of 0.09, 0.10, 0.11, 0.12, 0.13, or 0.14 lb/in3, or greater. As noted above, when averaged together, the density of the high-density composite portion(s) and the other portion(s) of the body (e.g., lower portion42), if any, should have an overall part density greater than 0.06 lb/in3, and more preferably about 0.08 lb/in3or greater. Based on the overall (averaged) part density, the weight of the rumble strip body having dimensions of 11 ft.×1.0 ft.×0.75 in. may be in a range from 75 to 150 lbs., for example.

In exemplary embodiments, it may be advantageous to use high-density filler material(s)36that are resistant to corrosion in a typical roadway condition where road salts such as sodium chloride may be present. This is because, although the high-density filler36(e.g., particles) generally will be encapsulated and protected by the flexible material matrix34, fissures may develop in the matrix34over time which can expose the high-density filler36to the corrosive elements. Many alkaline earth, transition, or post transition metal oxides, carbides, nitrides, sulfates, and the like, will exhibit corrosion-resistance in a typical roadway condition, and should improve over the corrosion susceptibility of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials.

As discussed above, it is preferable that the specific gravity of the high-density filler material36is greater than about 3.0, which may somewhat limit the available candidates of materials that also offer corrosion-resistance. The high-density fillers of PbO, ZnO, Fe3O4, and BaSO4depicted in Table 1 are some non-limiting examples of oxide and sulfate materials that are corrosion-resistant. The general corrosion resistance of such oxide, carbide, nitride, sulfate, etc. materials are in contrast with some pure metals or metal alloys, such as pure iron, cast iron, or plain carbon steel, for example, which generally form rust in the form of hematite (Fe2O3) which is an unstable oxide that spalls off and provides no corrosion-resistant effect. Thus, in exemplary embodiments, the rumble strip body is devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials; and also may be devoid of other pure metals/metal alloys that form an unstable oxide (e.g., those with a Pilling-Bedworth ratio of less than about 1 and greater than about 2).

In addition, some metal oxides, nitrides, carbides, sulfates, inorganics, minerals, etc. (such as some listed in Table 1), may be less expensive, less reactive, less toxic, more processible with the elastomer, etc., than their base metal itself. Therefore, the oxide, nitride, sulfate, etc. form of the high-density filler material36may be more desirable from this perspective as well, provided such material is suitable for increasing the density of the composite32without detrimental effects to the flexible material matrix34.

In addition to one or more of the foregoing attributes of providing high density (e.g., specific gravity greater than 3.0), general processability, corrosion-resistance, cost, availability, etc., it may be beneficial to use a high-density filler material36that also can be used as a processing aid to the polymer matrix material34(e.g., elastomeric). In exemplary embodiments, zinc oxide (ZnO) is a particularly attractive material because it may be used as an accelerator in polymeric (e.g., elastomeric) compositions. In this manner, the ZnO material may be added in a sufficient quantity as an accelerator to the polymer matrix material (e.g., elastomeric) composition, and then can be overloaded to an amount that achieves the desired composite layer32density and/or overall part density of the rumble strip body18. Zinc oxide is a readily-available, inexpensive, non-toxic, and corrosion-resistant material. Zinc oxide also has a specific gravity of about 4.4, meaning that an appropriate amount may be added to the composite composition without affecting the desired properties of flexibility, strength, etc. of the rumble strip body18. In exemplary embodiments, the ZnO is provided in the high-density composite32in an amount from about 500 phr to about 1100 phr (parts by weight per 100 parts by weight of total polymer(s) (e.g., total elastomer(s)) of the flexible polymer matrix34), and more particularly from about 600 phr to about 800 phr. In exemplary embodiments, the ZnO is added in powder form with a particle size having a range from about 0.1 micron to about 0.5 microns, more particularly 0.1-0.2 microns, to enable suitable performance of the rumble strip design.

While an exemplary form or forms of the portable roadway warning system10(and more particularly the exemplary portable rumble strip16) have been described above, it should be apparent to those having ordinary skill in the art that alternative configurations also could be employed. For example, although the rumble strip body18is shown and described with the high-density composite32forming at least the upper portion38, including the vehicle engagement surface20and at least a portion of the side surfaces24,26,27and28, the high-density composition32could instead form one or more intermediate layers or portions (e.g., within intermediate portion40) between the lower layer42and corresponding upper layer (each of which lower and upper layer might not contain high-density filler material as described above, or each of which may have a density less than 0.060 lb/in3). As indicated above, the different layers (e.g., lower, intermediate and upper layer) could each include different base materials, different fillers, and be of different sizes or locations to provide different functionality as may be desired. Although, as noted above, it is preferred that the high-density composite32, regardless of its location, is of sufficient density and size (based on its density) to provide the desired weight and road stability of the rumble strip body18, while still preferably enabling the overall flexibility of the rumble strip design.

Turning now toFIGS.7and8, another exemplary embodiment of a rumble strip116for a roadway warning system is shown in lateral cross-section (FIG.7) and longitudinal cross-section (FIG.8). The rumble strip116is similar to the above-described rumble strip16, and consequently the same reference numerals but indexed by 100 are used to denote structures corresponding to similar structures in the rumble strips16,116. In addition, the foregoing description of the rumble strip16is equally applicable to the rumble strip116, except as noted below. Moreover, aspects of the rumble strips16,116may be substituted for one another or used in conjunction with one another where applicable.

As shown, the rumble strip116includes an elongated body118having an upper vehicle engagement surface120, a lower roadway engagement surface122, and a leading edge124and trailing edge126between the upper and lower engagement surfaces120,122. Similarly to the rumble strip16, in exemplary embodiments the elongated body118of the rumble strip116has a length greater than its width, and its width greater than its thickness. Also in exemplary embodiments, the rumble strip body118may be a flexible body118to provide enhanced freedom of flexibility in multiple directions to aid in performance and portability of the rumble strip design, among other considerations. To achieve such flexibility, one or more portions of the rumble strip body118may be made with one or more suitably resilient or flexible materials, including processing aids and other constituents, such as those materials described above.

At least one difference between the exemplary rumble strip116and the above-described rumble strip16is that the high-density filler material136of rumble strip116is in the form of discrete unbound pieces of material disposed within a cavity137of the body118, instead of being discrete pieces dispersed and embedded in a polymer matrix as is the case with exemplary embodiments of the rumble strip16. Such a design with the discrete unbound pieces of high-density filler material136may enable a greater variety in the type of material that can be included in the rumble strip body118because dispersing the material within a matrix is not a concern. Moreover, because the discrete unbound pieces of the filler material136may be movable against each other and/or displaceable relative to each other within the cavity137, this may enable the rumble strip body118to maintain at least some flexibility by permitting deformations (flexion, compression, etc.) within the overall bulk of discrete unbound pieces in the cavity137. In addition, because the overall bulk of high-density filler material136is in the form of individual and preferably small pieces, each individual piece preferably would not have sufficient mass to create an impactful projectile if ejected from the rumble strip116in the event of catastrophic failure. Rather, the discrete unbound pieces of high-density filler136would be dispersed from the cavity137as a cloud, for example.

The discrete unbound pieces of high-density filler material136may include one or more types of material in any suitable form or forms. In exemplary embodiments, the discrete unbound pieces provide a bulk flowable material that partially or entirely fills the cavity137of the body118. The flowable material may be poured into the cavity137and may remain relatively loose to enhance deformability of the body118, or may be tamped or compacted as it fills the cavity137, or thereafter, to increase packing density. The flowable material may be a free-flowing material with a high-degree of flowability, or the flowable particulate may have a lower-degree of flowability with some cohesion between particles. Generally, a bulk flowable material enables at least some displacement of its constituent solid pieces relative to each other. The degree of flowability will be influenced by a variety of factors, such as friction between particles, Van der Waals or static forces, storage environment, moisture, etc. A suitable test method, such as with the use of a powder rheometer, may be used to determine the flowability. Generally, the higher degree of flowability of the material will enhance pourability into the cavity137and also may enhance flexibility of the rumble strip body118due to the easier movement of the particles against each other.

In exemplary embodiments, the discrete unbound pieces of high-density filler136include one or more types of particles which may be in powder form. The particles may have any suitable shape and size (or size distribution) as may be desired for the physical properties of the bulk material. The particles may be generally spherical or have a low aspect ratio, or may be irregular or have a high aspect ratio. Irregular particles generally will have greater resistance to flow but may provide improved compaction (green strength) if desired. The particle size for such powders may be in a range from about 0.1 microns to about 500 microns, for example. Finer particles generally have greater surface area and may have a higher resistance to flow. Larger pieces greater than 500 microns also could be used, such as pieces as large as about 1 millimeter (mm), or possibly greater. The greater the mass of each individual piece, however, the greater the impact force of the piece if ejected from the cavity137of the rumble strip body118(i.e., in the event of catastrophic failure). Therefore, pieces smaller than 1 mm, and more particularly a flowable powder having a mean size (D50) from about 100 microns to about 1,000 microns (1 mm) may be preferred. The discrete unbound pieces of high-density filler136also may include short-fibers, if desired, or may include aggregate particles composed of many small pieces adhered together. Such an aggregate particle still constitutes a discrete unbound piece that can be intermixed with and movable relative to other discrete unbound pieces of the high-density filler136in the cavity137.

The composition of the discrete unbound pieces of high-density filler136may include a single type of material or may include a mixture of different types of material. Generally, exemplary types of material used in the high-density filler136may be the same as the high-density filler36described above, including but not limited to, one or more of oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements. In the rumble strip116, however, because the high-density filler136is not dispersed within a matrix, there may be less concern over material interactions with the matrix material. In addition, depending on the encapsulation of the overall bulk of high-density filler136within the cavity137, there also may be less concern over environmental corrosion caused by road salts, for example. Accordingly, materials such as pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials may be utilized in the rumble strip116with reduced adverse effect. Thus, by way of example and not limitation, an inexpensive flowable iron powder could be dispensed as the high-density filler material136into the cavity137, or other pocket, in the rumble strip body118.

To facilitate the flowability of the high-density filler136, the composition of the high-density filler136may include materials other than high-density materials. For example, suitable lubricants, such as graphite, stearates (e.g., magnesium stearate), stearic acid, oils, or the like could be used in the composition. The lubricants may be chosen as desired based on their performance and compatibility with the high-density materials in the filler136. Alternatively or additionally, other suitable materials may be added to the composition of the high-density filler to aid in compaction or packing density, if desired.

Similarly to the above-described rumble strip16, the amount and type of material(s) in the composition of the high-density filler136should be chosen to provide an overall density of the rumble strip body118that results in sufficient pressure on the roadway surface for acceptable resistance to movement, such as for use in high-speed traffic conditions. Accordingly, in exemplary embodiments the high-density filler136is loaded into the cavity137in an amount that achieves an overall density of the rumble strip body118in the range from about 0.06 lb/in3to about 0.15 lb/in3, or more preferably at least about 0.08 lb/in3. The amount of high-density filler136(in both weight and volume percent) in the cavity137will vary based on the density (specific gravity) of the high-density filler material136(or combination of materials in the high-density filler136). Similarly to the rumble strip16, the body118of the rumble strip116may be made with polymer(s) (e.g., elastomer(s)) having a density of about 0.04 lb/in3to about 0.05 lb/in3; and because the desired overall density of the rumble strip body118preferably may be about 0.08 lb/in3or greater to achieve the desired weight and road stability for highway vehicle speeds, using a high-density filler material136(e.g., individually or as a mixture) with a specific gravity below 3.0 may make it difficult to attain the desired overall density of the body118. Thus, a specific gravity of the high-density filler136(e.g., the specific gravity of the material or mixture of materials) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example. Because some void space may be contained in the cavity137such as between individual pieces and/or in a head space of the cavity137, the calculation of void space may need to be accounted for in determining the desired specific gravity of the high-density filler136.

The cavity137in the rumble strip body118may be formed in any suitable manner with any suitable configuration as may be desired for the application. In the illustrated embodiment, the cavity137is a hollow chamber formed by internal surfaces141of the body118. For example, the rumble strip body118may be molded as a hollow article, and a fill port150may be provided at any suitable location to allow the discrete unbound pieces of high-density filler material136to be dispensed into the cavity137via the fill port150. A suitable closure152, such as a plug, is provided to close and seal the cavity137after a desired amount of the high-density filler136is dispensed into the cavity137. The amount of high-density filler136may at least partially fill the cavity137, or may entirely fill the cavity137with suitable void space to permit flowability of the filler136in the cavity thereby enhancing flexibility of the body118.

The cavity137may be located at any suitable position in the body118to account for weight distribution, flexibility, etc. In the illustrated embodiment shown inFIG.7, for example, the cavity137is essentially centrally located in the lateral direction of the body118and extends laterally along a majority of the width of the body118. As shown inFIG.8, the cavity137may extend in the longitudinal direction along at least a portion of the length of the rumble strip body118. To facilitate fillability, multiple cavities137may be provided in the body118, such as a plurality of longitudinally spaced apart cavities137each having a fill port150and at least partially filled with high-density filler136, which may be the same type of filler, or different types as desired.

In an alternative embodiment (not shown), the discrete unbound pieces of high-density filler136may be dispensed into a bag or bladder that is then co-molded with the rumble strip body118to form the cavity137filled with the high-density filler136. Any suitable bag or bladder capable of withstanding the processing conditions of molding the body118may be used. The bag or bladder filled with high-density filler136may be introduced at any step during the molding process and may be positioned at any suitable location. Multiple bags or bladders filled with high-density filler136may be used and positioned in the body118. In exemplary embodiments, the bag or bladder may be made with a compatible polymer (e.g., elastomer) that provides flexibility and which may enable co-vulcanization with the surrounding portions of the rumble strip body118.

Similarly to the rumble strip16, the body118of rumble strip116may be made of the same material (e.g., flexible polymeric, such as one or more elastomers), or may be made of different materials. For example, similarly to rumble strip16, the lower portion142of the rumble strip body118may be made with a softer polymer material the upper portion139. This may enable the lower portion142to better conform to an uneven roadway surface to enhance contact area, while enabling the upper portion139to better withstand highspeed vehicle impact. It is understood, however, that these relative hardnesses between portions139,142(or any other portions or layers) may be the same, or may be varied as desired. In exemplary embodiments, the upper portion139is integrally molded with the lower portion142(or one or more other layers, if any), such as via co-vulcanizing. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. Alternatively or additionally, the heated viscous material of one or both layers138,142(or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions138or142could be preformed and precured as a discrete article, and the other layer portion(s)138or142could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions138,142(or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive, such as an adhesive that provides porous wicking and/or crosslinking (after heating/curing) with one or both of the upper and lower portions138,142. Alternatively, the upper and lower portions138,132may form respective portions of an openable and closeable rumble strip body in the form of a container or case containing the discrete unbound pieces of high-density filler136.

Turning now toFIGS.9and10, another exemplary embodiment of a rumble strip216for a roadway warning system is shown in lateral cross-section (FIG.10) and longitudinal cross-section (FIG.9). The rumble strip216is similar to the above-described rumble strips16,116and consequently the same reference numerals but in the 200-series are used to denote structures corresponding to similar structures in the rumble strips16,116,216. In addition, the foregoing description of the rumble strips16,116are equally applicable to the rumble strip216, except as noted below. Moreover, aspects of the rumble strips16,116,216may be substituted for one another or used in conjunction with one another where applicable.

As shown, the rumble strip216includes an elongated body218having an upper vehicle engagement surface220, a lower roadway engagement surface222, and a leading edge224and trailing edge226between the upper and lower engagement surfaces220,222. Similarly to the rumble strip16, in exemplary embodiments the elongated body218of the rumble strip216has a length greater than its width, and its width greater than its thickness. Also in exemplary embodiments, the rumble strip body218may be a flexible body218. To achieve flexibility, one or more portions of the rumble strip body218may be made with one or more suitably resilient or flexible materials, including processing aids and other constituents, such as those materials described above.

At least one difference with the exemplary rumble strip216is that the high-density filler material236is in the form of one or more frangible articles236disposed within the rumble strip body218. In exemplary embodiments, the frangible article(s)236are brittle and easily breakable (e.g., can be broken by hand, such as with about 25 pounds of force). As shown in the illustrated embodiment, the one or more frangible articles236may be fixed within the rumble strip body218, such as being encased by the one or more materials forming the rumble strip body218. Such a design with the frangible article(s)236may enable a greater variety in the type of material that can be included in the rumble strip body218because dispersing the material within a matrix is not a concern. In addition, because the frangible article(s)236are brittle and easily breakable, if a piece of frangible article236were ejected from the rumble strip body218in event of catastrophic failure, the piece of frangible article would break and/or disintegrate on impact.

The frangible article(s)236may include one or more types of material in any suitable form or forms. The material or mixture of materials forming the frangible article236may be the same as those described above in connection with the high-density filler36and the high-density filler136. The material or mixture of materials constituting the frangible article236may be formed into any suitable structure as desired. For example, the material(s) constituting the frangible article236may be pressed into a green state to form the final frangible article236. Alternatively or additionally, a binder, such as a heat-sensitive binder, may be utilized to facilitate particle-to-particle bonding to form the frangible article236. The binder may be a weak binder or may be provided in minute amounts to facilitate fragility. The frangible article236may have a relatively high-porosity to facilitate fragility. The final shape of the frangible article236may be a bar, rod, slug, puck, brick, or any other suitable shape, which may be placed at any suitable location in the rumble strip body218.

Similarly to the above-described rumble strips16and116, the amount and type of material(s) in the composition of the frangible article236should be chosen to provide an overall density of the rumble strip body218that results in sufficient pressure on the roadway surface for acceptable resistance to movement, such as for use in high-speed traffic conditions. Accordingly, in exemplary embodiments the frangible article236is disposed in the rumble strip body218in an amount that achieves an overall density of the rumble strip body118in the range from about 0.06 lb/in3to about 0.15 lb/in3, or more preferably at least about 0.08 lb/in3. Also similarly to the rumble strips16and116, the body218of the rumble strip216may be made with polymer(s) (e.g., elastomer(s)) having a density of about 0.04 lb/in3to about 0.05 lb/in3, and to achieve a suitable overall density of the rumble strip body218, the specific gravity of the frangible article236as a whole (e.g., the average specific gravity of the material or mixture of materials forming the frangible article236) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example. Because the frangible article236may have porosity, the calculation of porosity may need to be accounted for in determining the desired specific gravity or density of the overall frangible article236.

Also similarly to the rumble strips16and116, the body218of rumble strip216may be made of the same material (e.g., flexible polymeric, such as one or more elastomers), or may be made of different materials. For example, the lower portion242of the rumble strip body218may be made with a softer polymer material than the upper portion239, or vice versa. In addition, the upper portion239may be integrally molded with the lower portion242(or one or more other layers, if any), such as via co-vulcanizing. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. Alternatively or additionally, the heated viscous material of one or both layers238,242(or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions238or242could be preformed and precured as a discrete article, and the other layer portion(s)238or242could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions238,242(or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive. Alternatively, the upper and lower portions238,232may form respective portions of an openable and closeable rumble strip body in the form of a case containing the frangible article(s)236.

An exemplary roadway warning device has been described herein, including a portable rumble strip that includes high-density filler material to achieve a desired overall density and roadway stability of the rumble strip such as for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts. In some exemplary embodiments, the filler is dispersed and embedded within a flexible polymer composite matrix of the rumble strip body. In some exemplary embodiments, the filler is in the form of discrete unbound pieces of material disposed within a cavity of the rumble strip body. In some exemplary embodiments, the filler is in the form of a frangible article disposed within the rumble strip body.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having a flexible polymeric material matrix and at least one filler dispersed in the matrix that enhances the density of the composite, wherein the at least one filler is included in an amount that provides an overall density of the elongated flexible body in a range from 0.06 lb/in3to 0.15 lb/in3.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having: a flexible elastomeric matrix, at least one filler dispersed in the matrix, wherein: the at least one filler has a density greater than a density of the flexible elastomeric material matrix; the at least one filler has a specific gravity of 3.0 or greater; and the at least one filler is included in the composite in an amount that enhances the density of the composite, such that an overall density of the elongated flexible body is in a range from 0.06 lb/in3to 0.15 lb/in3.

According to an aspect, a portable rumble strip includes an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, wherein the portable rumble strip includes a composite having a polymeric material matrix and a filler dispersed in the matrix in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix, wherein the density of the filler is greater than a density of the polymeric material matrix.

Embodiment(s) may include one or more features of the foregoing aspect(s), separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the flexible polymeric material matrix of the composite is co-vulcanized with the one or more additional portions of the body to form a unitary structure.

In some embodiments, the at least one filler is dispersed uniformly throughout the matrix of the composite such that the elongated flexible body is free to flex in multiple different directions at any location along the length of the body that corresponds with the composite.

In some embodiments, the at least one filler has a density greater than a density of the flexible polymeric material matrix.

In some embodiments, the at least one filler has a specific gravity of 3.0 or greater.

In some embodiments, the at least one filler is included in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.

In some embodiments, the flexible polymeric material matrix has a density of less than 0.060 lb/in3.

In some embodiments, the flexible polymeric material matrix includes a thermoset or thermoplastic elastomer.

In some embodiments, the at least one filler has greater corrosion resistance to sodium chloride than plain carbon steel.

In some embodiments, the at least one filler is in powder form, and an average particle size of the powder is in a range from 0.1 microns to 500 microns.

In some embodiments, the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.

In some embodiments, the at least one filler includes one or more of lead oxide (PbO), iron oxide (Fe3O4), zinc oxide (ZnO), or barium sulfate (BaSO4).

In some embodiments, the at least one filler that enhances the density of the composite is ZnO in an amount from 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.

In some embodiments, the composite, the at least one filler, and/or the flexible polymeric material matrix includes one or more additional materials.

In some embodiments, the composite forms at least one flexible layer that cooperates with one or more additional flexible layers comprising polymeric material such that the elongated flexible body of the rumble strip is free to flex in multiple directions, bend in a direction of the length to bring longitudinal ends of the body toward each other, or roll into a spiral in a direction of the length.

In some embodiments, the density of the composite layer is greater than a density of the one or more additional flexible layers, and an overall average density of all layers of the elongated flexible body in a range from 0.06 lb/in3to 0.15 lb/in3.

In some embodiments, the composite forms an upper layer including at least the upper vehicle engagement surface, and wherein the one or more additional flexible layers includes a lower layer including at least the lower roadway engagement surface.

In some embodiments, the lower layer is co-vulcanized and unitary with the upper layer to form a single unitary elongated flexible body that is portable as a single unit.

In some embodiments, the upper layer formed by the composite is harder than the lower layer.

In some embodiments, an entirety of the elongated flexible body bounded by its outer surfaces is formed by the composite having the flexible polymeric material matrix and the at least one filler dispersed in the matrix that enhances the density of the composite.

In some embodiments, the composite and/or the elongated flexible body is devoid pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials.

In some embodiments, the rumble strip is devoid of rigid metal inserts, such as those having a minimum size of greater than 10 mm.

In some embodiments, the rumble strip is devoid of a housing that contains the elongated flexible body and/or the composite, and more particularly a housing that is more rigid than that of the composite.

In some embodiments, the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without failure.

In some embodiments, the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without significant movement relative to pavement upon which the rumble strip rests, such as less than 1 inch of movement per impact.

In some embodiments, the composite is devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based filler material, and more particularly wherein the elongated flexible body is devoid of such filler materials.

In some embodiments, the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein the elongated body includes at least one cavity, and at least one filler in the form of discrete unbound pieces of material is disposed within the cavity.

Embodiment(s) may include one or more features of the foregoing aspect, separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the elongated body is a flexible polymeric body or contains flexible portions of the elongated body.

In some embodiments, the at least one filler enhances the density of the composite, and wherein the at least one filler is included in an amount that provides an overall density of the elongated body in a range from 0.06 lb/in3to 0.15 lb/in3.

In some embodiments, the discrete unbound pieces provide a bulk flowable material in the cavity.

In some embodiments, the discrete unbound pieces provide a free-flowing powder.

In some embodiments, the discrete unbound pieces have a mean size (D50) less than about 1 mm.

In some embodiments, the discrete unbound pieces is a flowable powder having a mean size (D50) from about 100 microns to about 1,000 microns (1 mm).

In some embodiments, the discrete unbound pieces include oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements.

In some embodiments, the cavity is a hollow chamber formed by internal surfaces of the elongated body.

In some embodiments, elongated body includes a fill port in fluid communication with cavity, and optionally a closure to close and seal the cavity.

In some embodiments, the discrete unbound pieces of filler are contained in a bag or bladder that co-molded with the elongated body to form the cavity.

In some embodiments, the bag or bladder is made with a polymer that provides flexibility and is co-vulcanized with surrounding portions of the elongated body.

In some embodiments, the elongated body includes multiple cavities containing the at least one filler, the multiple cavities being spaced apart from each other in the elongated body.

In some embodiments, one or more layers or portions of the elongated body have different properties, the one or more layers or portions being co-vulcanized together to form a unitary portion or entirety of the body.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein one or more frangible articles are disposed in the elongated body.

Embodiment(s) may include one or more features of the foregoing aspect, separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the elongated body is a flexible polymeric body or contains flexible portions of the elongated body.

In some embodiments, the one or more frangible articles enhance the density of the composite, and wherein the one or more frangible articles are included in an amount that provides an overall density of the elongated body in a range from 0.06 lb/in3to 0.15 lb/in3.

In some embodiments, the one or more frangible articles are fixed within the elongated body.

In some embodiments, the one or more frangible articles include a bar, rod, slug, puck, brick, or any other suitable shape.

In some embodiments, the one or more frangible articles include oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements.

In some embodiments, one or more layers or portions of the elongated body have different properties, the one or more layers or portions being co-vulcanized together to form a unitary portion or entirety of the body.

According to an aspect, a portable rumble strip for placement on a roadway in a roadway warning system includes filler material within a body of the rumble strip, the filler material being of a type and in an amount that increases the density of a rumble strip such that its mass can exert a pressure on the roadway to withstand impact from a vehicle, such as a passenger vehicle or heavy truck, without movement of the rumble strip relative to the roadway.

Embodiment(s) may include the foregoing aspect in combination with one or more features of the foregoing aspect(s) or embodiment(s) separately or in any suitable combination.

As used herein, the term “flexible” is used in its conventional meaning to those having ordinary skill in the art, especially to those with ordinary skill in the art of polymeric and elastomeric compounding. Flexibility testing may be achieved by a test method designed to test the resistance to crack growth of a solid polymer, such as an elastomer (e.g., rubber), after repeated flexing. A suitable test method is ASTM D813 (Crack Growth), which is usually measured in the mm growth of a crack, with a lower growth number indicating a better resistance to cracking and increased flexibility. Another suitable test method is ASTM D1052 (Cut Growth Flexing), which gives an estimate of the ability of rubber vulcanizates to resist crack growth of a pierced specimen when subjected to bend flexing. Yet another suitable test is ASTM D2632 which covers the determination of impact resilience of solid rubber from measurement of the vertical rebound of a dropped mass. Still another suitable test may be ASTM 1053 (Stiffness/Flexibility).

As used herein, an “operable connection,” or a connection by which entities are “operably connected,” is one in which the entities are connected in such a way that the entities may perform as intended. An operable connection may be a direct connection or an indirect connection in which an intermediate entity or entities cooperate or otherwise are part of the connection or are in between the operably connected entities. An operable connection or coupling may include the entities being integral and unitary with each other.

It is to be understood that terms such as “top,” “bottom,” “upper,” “lower,” “left,” “right,” “front,” “rear,” “forward,” “rearward,” and the like as used herein may refer to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference.

It is to be understood that all ranges and ratio limits disclosed in the specification and claims may be combined in any manner. It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one, and that reference to an item in the singular may also include the item in the plural.

The term “about” as used herein refers to any value which lies within the range defined by a variation of up to ±10% of the stated value, for example, ±10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.01%, or ±0.0% of the stated value, as well as values intervening such stated values.

The transitional words or phrases, such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “incorporating,” “made of/with,” “formed of/with,” “fabricated of/with,” and the like, are to be understood to be open-ended, i.e., to mean including but not limited to.