KR20040071280A - Matrix element magnetic pavement marker and method of making same - Google Patents

Abstract

A method of making a magnetic road marker having an array of magnetic road elements disposed in a predetermined pattern mutually joined by a carrier web is disclosed. After the array of magnetic road elements is attached to the road surface, a portion of the carrier web surrounding the magnetic road elements is removed or substantially degraded to dissipate, leaving an array of discrete magnetic road elements.

Description

Matrix element magnetic road marker and its manufacturing method {MATRIX ELEMENT MAGNETIC PAVEMENT MARKER AND METHOD OF MAKING SAME}

Safer, more efficient and more accessible citizen transportation is very important. Public service providers, transit vehicles, and emergency vehicles must be able to drive faster and safer on the road in a variety of weather conditions.

Inclement weather and even invisible sunlight or oncoming traffic lights pose particular problems for both conventional traffic systems and guidance systems that provide lateral vehicle control. Snowing conditions, fog, heavy rain, rubella and smoke are examples of vehicle drivers. Snowy weather is a particularly difficult driving condition for snowplow drivers who are trying to clean the lanes when snow is falling or the lane markers are covered by snow. In addition, the reduction in visibility caused by blowing snow has caused tragic accidents when motorists collide snow plows running slower than the surrounding traffic. Winter weather continues to challenge arbitrary intelligent transportation systems (ITS), where vehicles move closer to each other at higher speeds on crowded roads.

In addition to vehicles, other vehicles, such as farm animals, pets, firefighters, blind pedestrians, etc., may also benefit from control systems and / or guidance systems. A mobile robot equipped with a magnetic sensor can be guided and / or controlled, for example when moving the robot along an industrial assembly line. Peripheral and boundary recognition systems can be used in pet restraint systems. In addition, games often require defined boundaries, such as baseball foul zones and football out boundaries, and it is often desirable for toys and sports equipment to emit an audible signal once the indicated line is crossed.

Several alternative methods of sensing the lateral position of a vehicle on the road are known. One choice includes visual signals or markings and optical sensors. Systems that rely on optical sensors can be obscured by dust, ice or snow, and visibility can be damaged by fog, blowing snow, blowing dust, and the like. Moreover, in night use, a significant amount of energy is consumed to illuminate the signal or emit the beam from the sensor.

Another approach is to use radar reflector markers with the vehicle's radar system. Both marker and radar detection systems are more expensive than magnetic systems. In addition, metal radar reflective markers embedded in the road have problems of durability and corrosion.

Magnetic systems are not adversely affected by weather conditions and do not require expensive video or other radio frequency equipment. The operating cost of the magnetic system is kept low because the marker is inactive (no power is needed for the magnetic marker to function). Some magnetic markers can last for the life of the road (a typical road has a life of 6 to 8 years) and may still be reprogrammed as part of the road.

One magnetic marking system includes a series of magnetic "nail" embedded in a road. Since the magnetic field strength is reduced by three squares of the distance from such a bipolar magnetic source, the "nail" must be fairly closely spaced to generate a useful signal. Using the most powerful rare earth magnets to minimize size and maximize spacing makes material costs expensive. Drilling holes in the road and using rigid nails also leads to stress concentration and premature road failure, which may be exacerbated by the corrosion of the nail. Using simple ferrous metal spikes does not provide the desired alternating signal to effectively separate the position signal from noise.

Another magnetic marking system is the use of magnetic paint to create magnetic stripes on the roadway. It is difficult to obtain a sufficiently strong magnetic signal with a paint layer of normal thickness. When the thickness of the paint is increased to obtain a good magnetic signal, the durability of the paint can be reduced. Paint streaks can only be magnetized after they are dried. Specially designed magnetizing fixtures shall be placed along the strip. Since the jig creates a limit to the magnetic field, the coercive force of the magnetic material is limited to about 1000 oersteds, making it easy to erase.

Some previously known magnetic induction systems employ materials embedded in roadways, as disclosed in US Pat. Nos. 3,609,678 and 3,714,625. The disclosed polymeric magnetic materials are elastic and flexible, such as nitrile and silicone rubber and plasticized PVC. Elasticity refers to the restoration of the original form substantially after removal of the strain force. The '678 patent discloses, in one embodiment, a polymer magnetic tape or sheet laid flat in shallower channels inserted along edges or cut along roads within narrow channels or slots (columns 3, lines 4-6). The patent further explains that the magnet may be embedded in the pavement of the road instead of the open channel (columns 3, lines 31-32) The flux sensor is mounted on a vehicle traveling on the road. Can generate an electrical signal in response to a magnetic medium if the magnetic field is strong enough to be detected. It is stated that it should be at least 2 gauss, preferably at least 10 gauss, more preferably at least 100 gauss (Columns 4, 75 Rows to columns 5, 6).

Conventional conformable non-magnetic road marking sheet materials are known in the art and generally include materials that crosslink to form polymeric materials, such as elastomers, but not crosslinked in sheet materials, thereby providing the desired viscoelastic properties. Coherence means that the deformation can be done under load and that much of the deformation can be maintained after removal of the load. Examples of consistent non-magnetic road markings include US Pat. No. 4,490,432, US Pat. No. 5,316,406, US Pat. No. 4,069,281, and US Pat. No. 5,194,113.

The present invention relates to a magnetic road marker and a method of manufacturing the same, and more particularly to a system for guiding a vehicle and other moving objects along a roadway, a warehouse floor, and the like.

1 is a cross-sectional view of an array of exemplary magnetic road markers in accordance with the present invention.

2 is a cross-sectional view of the array of magnetic road markers of FIG. 1 attached to a road surface.

3 is a cross-sectional view of an array of other exemplary magnetic road markers in accordance with the present invention.

4 is a cross-sectional view of the array of magnetic road markers of FIG. 3 attached to a road surface.

5 is a cross-sectional view of an array of other exemplary magnetic road markers with a carrier web mounted on top in accordance with the present invention.

6 is a cross-sectional view of the array of magnetic road markers of FIG. 5 attached to a road surface.

7 is a cross-sectional view of the array of magnetic road markers of FIG. 5 embedded in a road.

8 is a schematic representation of an exemplary process for making a magnetic road marker in accordance with the present invention.

9 is a schematic representation of another exemplary process for making a magnetic road marker in accordance with the present invention.

10 is a schematic diagram of another exemplary process for making a magnetic road marker in accordance with the present invention.

11 is a schematic diagram of an array of exemplary magnetic road markers in accordance with the present invention.

12 is a schematic diagram of an inventive control and / or guidance system in accordance with the present invention.

Ideally, these drawings are not to scale and are intended to be non-limiting.

The present invention relates to a magnetic road marker having an array of magnetic road elements joined together by a removable or breakable carrier web, which is consistent and minimizes unnecessary materials, improves tamping efficiency and is isolated from adjacent magnetic road markers. . Various methods of manufacturing arrays of magnetic road elements are also disclosed. The invention also relates to a method of attaching the array of magnetic road elements on a road surface.

The magnetic road marker of the present invention uses less material than conventional magnetic road markers because the mating layer is substantially removed. Tamping efficiency is also improved by isolating the tamping force on the discrete magnetic road elements. In particular, the magnetic road element acts as a force concentrator directed against tamping force applied to enhance the adhesion of the marker material to the road surface. In one embodiment, the arrays of discontinuous magnetic road elements are not substantially mutually coupled, such that interfacial delamination of a single road element does not adversely affect adjacent magnetic road elements. In some embodiments, the carrier web has sufficient matching so that the movement of individual magnetic road elements does not adversely affect adjacent magnetic road elements.

In one embodiment, a method of manufacturing a magnetic road marker includes forming an array of magnetic road elements that are mutually coupled by a carrier web so that they are typically arranged in a predetermined desired pattern. The breakable bond is formed between the magnetic road element and the carrier web.

Forming magnetic road elements mutually coupled by the carrier web is performed by integrally forming the magnetic road element and the carrier web, attaching the magnetic road element to the carrier web, or attaching the carrier web to the top surface of the magnetic road element. Can be. Forming a breakable bond between the magnetic road elements and the carrier web includes partially cutting the carrier web around a single magnetic road element or around a group of magnetic road elements.

In one embodiment, the magnetic road element has magnetic particles dispersed in the binder. The magnetic particles can be oriented to generate a magnetic field. In addition, polarity can be induced in the magnetic road elements. The magnetic road element may be composed of a coherent polymeric material or an incompatible polymeric material. Magnetic road elements may be in various forms, such as ropes, sheets, perforated articles, and the like. The form is mainly defined by the particular use of the article. The magnetic road element may be selected from the group consisting of polymers, ceramics, metals and metal alloy magnets.

The carrier web may be selected from the group consisting of polymer films, paper, liners, screens, mats, nonwoven webs, open scrims, or films of water soluble or aqueous dispersible polymer materials or nonwoven webs. After attaching the array of magnetic road elements to the road surface, the portion of the carrier web surrounding the magnetic road elements is removed, leaving an array of discrete magnetic road elements. The carrier web is coherent, preferably extensible.

In a variant, the magnetic road markers comprise magnetic road elements formed in a predetermined pattern on the carrier web. The carrier web has a fractureable portion between adjacent magnetic road elements. Preferably, the breakable portion can be substantially degraded when exposed to road conditions for a short period of time. A pressure sensitive adhesive may be applied to the back side of the magnetic road element, on which a separate liner is attached. The carrier web serves to maintain the array of magnetic road elements in a predetermined shape until the magnetic road elements are attached to the road surface. Subsequently, the carrier web degrades, leaving an array of discrete magnetic road elements that are separated in substantially the same shape as when in the carrier web.

In another embodiment, the magnetic road element has a pressure sensitive adhesive on its bottom surface. The surface of the magnetic road element coated with the adhesive is placed in an array on the separation liner. The carrier web is attached to the top of the magnetic road element to maintain the spacing orientation of the array when the separation liner is removed.

The invention also relates to a method of attaching an array of magnetic road elements to a road surface. The separation liner is removed from the array of magnetic road elements. An adhesive, such as a pressure sensitive adhesive, is interposed between the magnetic road element and the road surface. The portion of the carrier web surrounding the magnetic road element is removed from the array. In another embodiment, the array of magnetic road elements is formed in a predetermined pattern on the mating carrier web.

The invention also relates to a magnetic road article. The array of magnetic road elements of a predetermined pattern are mutually coupled by a carrier web. The breakable bond is disposed between the magnetic road element and the carrier web.

The array of magnetic road elements can be magnetized in a single pattern, but preferably magnetized in a pattern that produces an alternating magnetic signal that can be easily detected by the sensor. However, to convey more detailed information, the articles of the present invention may be magnetized ("encoded" or "recorded") in more complex patterns, such as those found in bar codes, credit card strips or magnetic tape recordings.

Magnetic road markers are non-powered, meaning that no external power source is required to transmit or receive signals. In this regard, the invention can be distinguished from powered landfill articles such as those typically used to determine whether a vehicle on a road has stopped at an intersection, for example a red light. This type of embedded sensor also requires power, but the present invention can be distinguished from the present invention in that it is a non-powered magnetic field source. The non-powered magnetic road markers of the present invention can also be used at remote points where installation time is short, requires less maintenance and requires no operating costs, and where power sources are not readily available. Thus, the non-powered magnetic road marker of the present invention provides several advantages over conventional embedded powered articles.

Another embodiment of the invention is an induction system for guiding a vehicle or moving body traveling on a road surface. The guidance system provides information to and / or controls the vehicle or the vehicle driver or other vehicle or system. Magnetic road elements may be disposed under existing traffic support structures or mounted on road surfaces. Discontinuous magnetic road elements are far less likely to be damaged by vehicle traffic or by mismatches in thermodynamic and mechanical properties between the road surface and the discontinuous magnetic road elements. In one embodiment, the guidance system comprises an array of magnetic road elements according to the invention attached to a road surface and a sensor passing over the array. The sensor can detect magnetic signals of the array of magnetic road elements. The output of the sensor is a lateral offset signal as needed. The output of the sensor may control the vehicle and / or provide information to the driver via the display unit.

A method of providing a guidance system for a traffic support structure is another aspect of the present invention. The present invention can also be used with magnetic induction of a snowplow. It is important that snowplows are properly placed on the traffic support structure to prevent inadvertent damage to curbs, roadside signs, and mailboxes. Since the lane markers may be covered by snow or ice on the road, it is advantageous for the snowplow driver to have a magnetic guidance system of the type described above so that the snowplow is held above the traffic support structure. The present invention may be particularly advantageous for inducing snowplows in whiteout (severe blizzard) conditions where visual guidance is limited. Other useful applications include electronic "rumble strips" that warn the driver that a vehicle has approached the edge of a traffic support structure or a school area, bridge deck, curbstone of the traffic support structure, or the entrance or exit of an unclear traffic support structure. And as a component of an automated freeway system in which the vehicle is automatically guided in the assigned lanes. As used herein,

"Consistent" means low unload energy of less than 125 g / cm (0.7 pounds / inch) and inelastic at 25 ° C. of greater than about 10%, preferably greater than 20%, more preferably at least 30% Refers to a carrier web showing deformation.

The term "breakable engagement" refers to a coupling between a carrier web and a magnetic road element (or in some embodiments, a carrier web attached to a single road element) that is easily breakable or destructive after attaching the magnetic road element to the road. Segment of the carrier web between a small portion of the carrier and the rest of the carrier web).

By “breakable portion” is meant a carrier web portion that is easily fractured or destructible, such as biodegradable, water soluble, or substantially degradable.

"Substantially deteriorated" refers to the degradation and dissipation of the carrier web when exposed to various environmental factors such as erosion, rain and impact from road traffic to form an array of discrete magnetic road elements.

1 is a side cross-sectional view of a magnetic road marker with an array 20 of magnetic road elements in accordance with a first embodiment of the present invention. The array 20 includes a plurality of magnetic road elements 24 and an integrally formed carrier web 22. In the illustrated embodiment, the magnetic road element 24 has permanent magnetization material 25 interspersed in the binder 27. The adhesive 26 is pattern coated on the bottom surface 28 of the magnetic road element 24. The adhesive 26 may alternatively be coated over the entire surface of the carrier web 22 and the magnetic road element 24 without being applied to the gaps of the carrier web 22. In the embodiment illustrated in FIGS. 1 and 2, the magnetic road element 24 and the carrier web 22 are formed of the same material. Separation liner 30 extends across adhesive 26 as needed until particularly ready for use of array 20 in embodiments where adhesive 26 is a pressure sensitive adhesive. Top surface 36 of magnetic road element 24 may include non-slip particles as needed. The anti-skid particles are embedded in the magnetic road element 24 or attached with an adhesive. Around the periphery of the magnetic road element 24 a breakable engagement 32 is typically formed by die cutting so that the carrier web 22 can be removed after mounting. The breakable engagement portion 32 has sufficient strength to releasably couple the magnetic road element 24 and the carrier web 22 until the array 20 is attached to the road surface 42 (see FIG. 2). It is preferable.

2 is a side cross-sectional view of the array 20 of FIG. 1 attached to the road surface 42. The separation liner 30 is removed and the array 20 is tampered with the road surface 42. The magnetic road element 24 acts as a concentrator that directly concentrates the tamping force at the interface between the adhesive 26 and the road surface 42. In the embodiment where the adhesive 26 is coated over the entire surface of the carrier web 22, the magnetic road element 24 minimizes the tamping force applied to the carrier web 22.

Subsequently, the carrier web 22 surrounding the magnetic road element 24 is removed or peeled from the array 20 by breaking the breakable engagement portion 32. As a result, an array of magnetic road elements 24 is disposed above the road surface 42 substantially identical to the structure held by the carrier web 22 of the array 20. Since the discontinuous magnetic road elements 24 are not interconnected by the carrier web 22, interfacial peeling of a single magnetic road element usually does not adversely affect adjacent magnetic road elements. The array 20 has a high degree of coherence with the surrounding road surface 42, so that the mismatch of thermodynamic and mechanical properties between the road surface 42 and the discontinuous magnetic road elements 24 can be well controlled.

3 is a side cross-sectional view of an array 50 of other magnetic road elements 52 attached to the carrier web 54 in various ways. Adhesive 56 is applied to the entire bottom surface 57 of the carrier web 54 or below the magnetic road element 52. The separation liner 58 is then attached to the adhesive 56 until the array 50 is ready for use. The carrier web 54 is coherent, breakable, and preferably stretchable. The list of carrier webs includes, but is not limited to, polymer films, paper, liners, screens, mats, nonwoven webs, and open scrims. In the embodiments of FIGS. 3 and 4, the magnetic road elements are polymer magnets, ceramics. It can be a coherent or non-coherent magnet, including magnets, metal magnets, and metal alloy magnets. The magnetic road element 52 may be attached with a plurality of retroreflective beads 55 using adhesive 59 as needed, as disclosed in US Pat. No. 4,988,541 (Hedblom).

4 is a side cross-sectional view of the array 50 of FIG. 3 attached to the road surface 42. The separation liner 58 is removed and the array 50 is tampered with the road surface 42. The carrier web 54 forms a breakable portion 60 between adjacent magnetic road elements 52. The breakable portion 60 is preferably capable of substantially deteriorating when exposed to road conditions. As shown in FIG. 4, the breakable portion 60 gradually degrades, leaving an array of discrete magnetic road elements 52 having substantially the same pattern as the carrier web 54 before being attached to the road surface 42. do. In a variant, a series of slits 62 may be formed as needed around the periphery of the magnetic road element 52. The portion of the carrier web 54 that surrounds the magnetic road element may be stripped or removed as needed, as shown in FIG. 2.

In yet another embodiment, the carrier web 54 is consistent and extensible. As a result, the array 50 of magnetic road elements 52 is disposed above the road surface 42 substantially the same as the structure held by the carrier web 54. The magnetic road elements 52 are interconnected by a portion 63 (shown in dashed lines) of the carrier web 54, while the coherent and / or extensible carrier webs 54 are relative to the surrounding road surface 42. By providing a high degree of consistency, the mismatch of thermodynamic and mechanical properties between the road surface 42 and the discontinuous magnetic road elements 24 can be well controlled.

5 is a cross-sectional side view of an array 100 of other magnetic road elements 102 with adhesive 104 on the bottom surface 106. Bottom surface 106 is disposed in an array over separation liner 108. The carrier web 110 is attached to the top of the magnetic road element 102, preferably by an adhesive, to maintain the spatial orientation of the array 100 when the separation liner 108 is removed. In one embodiment, the adhesive used to attach the carrier web 110 to the magnetic road element 102 has a lower peel strength than the adhesive 104 for the bottom surface 106 or the road surface 42. In another embodiment, the carrier web 110 is a membrane or nonwoven web of a biodegradable material, such as paper, or a water soluble or aqueous dispersible polymer material. In a variation, the carrier web 110 may be a conformable and extensible material.

6 is a side cross-sectional view of the array 100 of FIG. 5 attached to the road surface 42. In one embodiment, the separation liner 108 is removed and the array 100 is tampered with the road surface 42. The carrier web 110 may then be removed leaving the array of magnetic road elements 102 above the road surface 42. Alternatively, the carrier web 110 may be substantially degraded. For inlaid or underlaid embodiments discussed in connection with FIG. 7, the carrier web 110 may be a mating and / or extensible material as needed.

7 shows that the magnetic road element 105 is underlaid and the magnetic road element 107 is inlaid over the irregular road surface 42. Road surface 42 is a traffic support structure such as base material, asphalt, gravel, concrete, cement, brick, wood, soil and / or clay. An array of magnetic road markers 100 is attached to traffic support structure 42 using one of the techniques described above. FIG. 7 shows the embodiment of FIG. 6 for illustrative purposes only. Road surface layer 109 is then applied to underlay / inlay magnetic road elements 105, 107 within road surface 42 ′. Here, underlaid is defined as substantially surrounded by traffic support structures in all respects. Here, inlaid is defined as being at least partially surrounded by a traffic support structure.

Another structure for magnetic road markers is US patent application Ser. No. 08 / 682,477, titled Consistent Magnetic Articles for Use on Traffic Supporting Surfaces, Methods for Making the Same, Systems and Uses Including Them; US Patent No. 5,853,846, a conformal magnetic article underlaid under a support surface.

Adhesives known to be suitable for attaching articles to road surfaces include pressure sensitive adhesives, hot melt adhesives, hot melt pressure sensitive adhesives, contact adhesive cement, thermosetting adhesives and two-part epoxy adhesives. Some of these alternative adhesives are preferably interposed between the magnetic road marker and the road surface 42 prior to attachment, rather than being coated over an array of magnetic road elements.

8 is a schematic diagram of one embodiment of a compression and embossing method 130 for fabricating an array of magnetic road elements 132 in accordance with the present invention. The expression magnetic road marker refers to a completed magnetic road marker or protrusion that can be processed continuously to form magnetic road markers, for example, by orienting magnetic particles 135 interspersed with binder 137. The precursor sheet 134 is embossed by the embossing roll 136 to form protrusions 144 of a particular shape and dimension connected by the portion of the elastomeric sheet 134 forming the base sheet 145 as a permanent magnetization material.

Adhesive 138 is applied by coating roll 140. Liner 142 is attached to adhesive layer 138. Alternatively, the assembly with pressure sensitive adhesive 138 and liner 142 may be laminated simultaneously to the back side of the embossed magnetic road element 132. Subsequently, the protrusion 144 formed on the embossed sheet is subjected to a die cutting 146 process to form a breakable bond 148 between the base sheet 145 and the protrusion 144. Magnetic road element 132 may be attached to the road surface as shown in FIGS. 1 and 2 as a whole.

Precursor sheet 134 may be comprised of various polymeric magnetic materials, as disclosed in US Pat. No. 4,497,722 to Tsuchida et al. Additional exemplary materials for forming precursor sheet 134 include acrylonitrile-butadiene polymers, millable urethane polymers, neoprene and road marking materials disclosed in US Pat. Nos. 5,194,113 (Lasch et al.) And 5,127,973 (Sengupta et al.). It includes. Extender resins, inorganic fillers (eg silica) and reinforcements may also be included. The array of magnetic paint markers may be prepared using various techniques, such as those disclosed in US Pat. Nos. 4,388,359, 4,086,388, 4,988,541, and 5,194,113 (Lasch et al.).

9 is a schematic diagram of another method 130 'for manufacturing an array of magnetic road elements 132' in accordance with the present invention. A series of die cuts 148 'are formed in the precursor sheet 134' of magnetic material by the die cutting rolls 136 'to form the magnetic road elements 144'. The magnetic material may be coherent or inconsistent. Die cutting roll 136 ′ may be configured to cut various patterns into precursor sheet 134 ′, such as the array shown in FIG. 11. Adhesive 138 'is coated by coating roll 140'. Coherent and / or extensible carrier webs 142 'are attached to the layer of adhesive 138'.

In embodiments where the carrier web 142 'is consistent, a portion of the magnetic road element 144' is removed from the station 146 'to form an array of magnetic road elements (see Figure 11). In embodiments where the carrier web is extensible, the carrier web 142 'is biaxially stretched before or during attachment to the road surface 42, thereby separating or gaping between adjacent magnetic road elements 142'. Can be formed. Magnetic road elements may be attached to the road surface as described above.

10 is a schematic diagram of a casting and curing method according to the present invention. The polymer material containing permanent magnetized particles is extruded from the screw extruder 152 through the nozzle 150 to form a bank or tip of molten material at an orifice between the steel forming drum 156 and the doctor drum 158. The circumferential surface of the drum 156 includes a series of cavities 160 in the form of an intaglio of the desired magnetic road element 162. Molten material 154 fills and solidifies cavity 160 to form a series of magnetic road elements 162 over extensible carrier web 168. Extruder 152 preferably measures the amount of polymer material. Alternatively, a cutting tool, such as a roller or doctor blade, can be used to scrape excess polymer material from roller 156 before assembly 166 engages roller 156. The polymeric material is preferably a thermoplastic polymer or a polymer that is subsequently cured to become a thermoset polymer. The polymeric material may also include inorganic fillers and reinforcing materials such as glass beads, ceramic particles, microparticles of glass or ceramic, and / or glass fiber strands.

In addition, an assembly 166 comprising a carrier web 168, a pressure sensitive adhesive 170, and a separation liner 172 enters the nip between the drums 156, 158. Pulled into the nip containing the molten material 154, the carrier web 168 fuses with the magnetic road element 162 and is inseparably integrated.

The array 174 of magnetic road elements 162 then undergoes a die cutting 176 process of cutting the web 168 at least partially around the periphery of the magnetic road elements 162. In one embodiment, die cutting step 176 cuts the carrier web 168 and not the pressure sensitive adhesive 170 as needed, but not the liner 172. The magnetic road element undergoes further processing, such as the application of reflective material before or after the die cutting step.

In a variant, as shown in FIGS. 1 and 2, the gap formed by the nip between the drums 156, 158 is such that a thin web of thermoplastic composition is formed over the web 168 between the magnetic road elements 162. Increase as much as possible. A subsequent die cutting step 176 preferably cuts the thin web and carrier web 168 around the perimeter of the magnetic road element 162. Other methods of forming magnetic road markers on a carrier web are disclosed in US Pat. Nos. 5,152,917 (Pieper et al.), 5,435,816 (Spurgeon et al.) And 5,500,273 (Holmes et al.).

If the molten material 154 is semi-liquid when separated from the drum 156, the orientation of the desired magnetic particles may be caused by exposure to the permanent magnet or electromagnet 161. Mechanical work, such as occurs during extrusion or calendering, and / or externally applied magnetic fields will also promote orientation. The orientation makes it possible to obtain the desired magnetic performance.

In a variant, a rotary screen hot melt coater is used to coat the pattern corresponding to the magnetic road elements. The thermoplastic material is first heated to molten state and fed to the die. The die coats the molten material on a screen with a specific pattern and places the molten material on the first surface of the web or the breakable carrier with the adhesive and the separation liner on the second surface. The depth and sharpness of the pattern can be controlled by the die slot, the speed of the belt and / or the viscosity of the thermoplastic material. The resulting assembly is then subjected to a die cutting process that at least partially cuts the carrier web around the perimeter of the magnetic road element. This embodiment of the present invention can be performed using a rotary screen hot melt pattern coater available from May Coating Technologies, White Bear Lake, Minnesota.

In another embodiment, insert molding (injection molding) techniques may be used to form the magnetic road elements according to the present invention. A breakable carrier web can be inserted into a mold and a magnetic road element can be molded over the top of the carrier web. Once the assembly has cooled, the magnetic road elements are taken out of the mold, the carrier web is indexed forward and the molding process is repeated. Injection molding has the advantage of being relatively fast and widely available. Other process techniques for manufacturing magnetic road markers according to the present invention are filed and assigned jointly on U.S. Pat.Nos. 5,201,916 to Berg et al., 5,304,331 to Leonard et al. Matrix element road markers and methods of making them are disclosed in US patent application Ser. No. 10/039957.

11 illustrates an array 210 of exemplary magnetic road elements 212, 214 on a carrier web 216 in accordance with the present invention. The array 210 of the present invention may have alternating polar sections along its length as shown by the + mark on the discontinuous element 212 and the − mark on the element 214 by the transition region 213. . In the case of traditional magnetic road marking applications, the polarities alternate about every meter. The heights of the magnetic road elements 212, 214 of the illustrated embodiment range from about 0.25 mm to about 1.0 mm (0.010 to 0.040 inch), less than 3 mm (0.118 inch). It should be noted that magnetic road elements may be used at other heights as needed.

The array 210 preferably has columns and rows of magnetic road elements 212 and 214 spaced apart by a distance of about 250 mm to about 5 mm, while the spacing between the magnetic road elements does not interfere with the integrity of the array. It can be as close as possible. The planar dimension or width of the magnetic road element is usually from about 3 mm to about 10 mm, but other width elements may be used in accordance with the present invention. The spacing of magnetic road elements 212, 214 in the array 210 varies depending on the height of the magnetic road element and the particular application in which the magnetic road element is used.

Recursive Reflective Magnetic Road Marker

The magnetic road marker of the present invention may be coated with retroreflective beads by various techniques, as disclosed in US Pat. No. 4,988,541. Suitable bead adhesive materials for attaching the beads are preferably thermoplastic or thermoset polymer binders. One such binder is a vinyl-based thermoplastic, including white pigments, as disclosed in US Pat. No. 4,117,192. Other suitable bead adhesive materials include two-part polyurethanes formed by reacting polycaprolactone diols and triols with derivatives of hexamethylene diisocyanate and epoxy resins disclosed in US Pat. Nos. 4,248,932, 3,436,359, and 3,580,887. And the blocked polyurethane compositions disclosed in US Pat. No. 4,530,859. Other suitable bead adhesive materials include polyurethane compositions comprising a water activated curing agent and a polyisocyanate prepolymer. The moisture activated curing agent is preferably an oxalolidene ring as disclosed in US Pat. No. 4,381,388.

Particles such as retroreflective beads suitable for use in the process include glass beads formed from glass materials having a refractive index (n) of about 1.5 to about 2.26, more preferably about 1.5 to about 1.9. As is well known in the art, glass beads of a material having a refractive index of about 1.5 are less expensive and have better scratch and chip resistance than glass beads of a material having a refractive index of about 1.75 to about 2.26. However, cheaper and more durable glass beads are less efficient retroreflectors. In one embodiment, the glass beads may comprise a coating of silver or other mirror reflective metal or dielectric. The unembedded silver coating portion is then removed to provide a highly efficient retroreflector. In another embodiment, the beads with a hemispherical coating of mirror reflective metal, such as silver, are attached to the liquid bead adhesive layer. Since the beads are optionally oriented when attached, some of the beads are embedded in an orientation that is efficient for retroreflective reflection. In general, efficiently oriented beads have an uncoated exposed surface and a buried layer coated with silver.

Preferred retroreflective beads are disclosed in US Pat. No. 4,564,556 and US Pat. No. 4,758,469. These beads are generally described as a solid, transparent, non-glassy ceramic ellipsoid comprising at least one crystalline phase composed of at least one metal oxide. These beads may also have an amorphous phase such as silica. The term non-vitreous means that it does not derive from the melt or mixture of raw materials that become liquid at high temperatures such as glass. These spheroids are very resistant to scratching and chipping, have a significant hardness (eg, 700 Knoop or more), and can be produced with relatively high refractive indices (1.4 to 2.6). Examples of compositions of these beads are zirconia-alumina-silica and zirconia-silica.

The retroreflective beads have a diameter that is compatible with the size, shape, spacing and geometry of the magnetic road elements present on the base sheet. In the case of the base sheet 100 described above, it is appropriate to use beads of 50-350 μm diameter. Another factor influencing bead size is the number of rows of beads desired to be used for vehicle headlights. Only a side of about 380 μm can be seen at an angle of about 2-3 degrees from the base sheet 100. Thus, only one row of about 300 μm beads can be seen or only two rows of about 225 μm beads.

Binder Material for Coherent Magnetic Layer

In one embodiment of the invention, the coherent magnetic road element is formed by interspersing a plurality of magnetic particles in a binder. There is a sufficient amount of magnetic particles to provide a magnetic signal to the sensor through the traffic support structure. Typically the magnetic particles are non-spherical.

In some organic binder embodiments, for example, if the organic binder comprises a non-crosslinked elastomeric precursor (see, eg, US Pat. No. 4,490,432), using a conventional rubber treatment method, heavy duty, single or It is desirable to produce a coherent magnetic layer such as a continuous rubber kneading machine, such as a Banbury mixer or a double screw extruder.

Here, "elastomer precursor" is used to refer to a polymer that can be crosslinked, vulcanized or cured to form an elastomer. An "elastomer" is a material that can be stretched to at least about twice its original dimensions without rupturing and can quickly return to its original dimensions substantially upon release of the stretching force. Examples of useful elastomeric precursors include acrylonitrile-butadiene polymers, neoprene, polyacrylates, natural rubber and styrene-butadiene polymers. Extender resins, preferably halogenated polymers, such as chlorinated paraffins, also hydrocarbon resins, polystyrenes or polycyclodienes, are included in the non-crosslinked elastomeric precursor component, or are mixed with the elastomeric precursor component or form a single phase with the elastomeric precursor component. Extender resins preferably amount to at least 20 parts by weight of the organic components of the conformable layer when using this binder.

Useful thermoplastic reinforcing polymers are known in the road marking art (eg, polyolefins, vinyl copolymers, polyethers, polyacrylates, styrene-acrylonitrile copolymers, polyesters, polyurethanes and cellulose derivatives).

In another embodiment of the invention, the conformable layer comprises two main components: soft thermoplastic polymer and unreinforced magnetic inorganic fine particles. The thermoplastic polymer is preferably a polyolefin. These binders are generally described in US Pat. No. 5,194,113.

Magnetic particles

The most suitable choice of magnetic material is the composition of permanent magnetic material particles interspersed with a matrix of organic binders. Many kinds of magnetic particles that can be residual magnetized are known to those skilled in the art of magnetic materials.

The major axis length of such particles suitable for use in the present invention is from about 10 nanometers to about 1 mm. Preferred ranges are from about 0.1 μm to about 200 μm. The saturation magnetization of the magnetic particles is about 10 to about 250 emu / g (electromagnetic units / gram), preferably greater than 50 emu / g. The coercive force of such particles is about 100 to about 20,000 oersteds, more preferably about 200 to about 5000 oersteds. Particles with coercivity of less than about 200 oersteds are too easy and inadvertently demagnetized, and particles with coercive forces of more than 5000 oersteds require relatively expensive equipment to fully magnetize.

One type of high performance permanent magnet particles is a rare earth metal alloy type material. Examples of incorporation of such particles into polymeric binders include US Pat. No. 4,497,722, which discloses the use of samarium-cobalt alloy particles, and neodymium-iron-boron. European Patent Application No. 260,870 which discloses the use of alloy particles. Such particles are most undesirable in the present application because the alloys are relatively expensive and may be excessively corroded under prolonged external exposure conditions, and the coercive force of such alloys typically exceeds 5000 oersteds.

In addition, permanent magnet particles of many kinds of metals or metal alloys may be used, but are not the most preferable. Such alloys include Alnico (aluminum-nickel-cobalt-iron alloy), iron, iron-carbon, iron-cobalt, iron-cobalt-chromium, iron-cobalt-molybdenum, iron-cobalt-vanadium, copper- Nickel-iron, manganese-bismuth, manganese-aluminum and cobalt-platinum alloys.

Another magnetic material is a kind of stable magnetic oxide material known as magnetic ferrite. One particularly preferred material is the hexagonal phase of the magnettoplumbite structure, widely known as barium hexaferrite, which is generally produced as a flat hexagonal plate. Strontium and lead can partially or completely replace barium, and many other elements can partially replace iron. Therefore, strontium hexalephite is also a preferred material. Another preferred type of material is cubic ferrite, which is sometimes produced as cubic particles, but more often as long needle or needle shaped particles. These examples include magnetite (Fe ₃ O ₄ ), magnetite or gamma ferrite oxide (gamma-Fe ₂ O ₃ ), intermediates of these two compounds and cobalt replacement variants of these two compounds or their intermediates. Include. All of these magnetic ferrites are mass produced at relatively low cost and are stable under long external exposure conditions. Their coercive force belongs to the most preferred range of 200 to 5000 oersteds.

Chromium dioxide is another alternative material that may be useful as magnetic particles in the present invention because of its low Curie temperature, which facilitates the method of thermomagnetic magnetization.

Magnetic particles are generally scattered within the polymer matrix at high loads. The magnetic particles make up at least 1% by volume of the magnetic layer, and it is difficult to include an amount of particles that make up about 75% or more by volume of the material. The magnetic road markers preferably have a binder that constitutes at least 30% by volume of the magnetic particles. The preferred loading range is about 30 to 60 volume percent, more preferably about 45 to about 60 volume percent. In order to obtain the highest residual magnetization, the particles are preferably anisotropic particles of substantially domain size, and there is preferably a substantially parallel alignment of the desired magnetic axis of the sufficient number of particles such that the magnetic material itself is anisotropic.

Preferred particulate materials are ferrites in the form of substantially plate-shaped, in particular barium, lead and strontium ferrite, which have a preferred magnetic axis perpendicular to the general plane of the plate. However, other materials with permanent magnetism may also be used, such as iron oxide particles or particles of manganese-bismuth or iron protected against oxidation.

As known in the art and referenced above, the orientation of magnetic particles may be optimized by physically oriented (eg, calendaring) the particles.

In the case of an exemplary array of magnetic road elements having a width of about 10 cm and an average magnetic thickness layer of about 0.1 cm, the magnetic field at the surface of the article is about 10 gauss, the magnetic field at a distance of about 5 cm is 5 gauss, The magnetic field at a distance of about 10 cm is 2 gauss, and the magnetic field at a distance of about 15 cm is 1 gauss. Thus, if the array is underlaid about 10 cm below the traffic support structure, the magnetic field strength at the traffic support surface is approximately 2 gauss, which is considered sufficient to be detected by the sensor. Of course, stronger or weaker magnetic fields may be produced by the array of magnetic road elements, depending on the materials and processes used to make the article.

The array of magnetic road markers of the present invention may be attached to the road surface by hand or by a machine. The magnetic road marker of the present invention may be installed as part of a road surface using any one of a variety of devices, such as manual dispensers, truck rear mounted dispensers, and truck built dispensers. For example, US Pat. No. 4,030,958 discloses a suitable truck rear mounted dispenser for attaching an article of the invention in the form of a tape with adhesive applied to the back, and US Pat. No. 4,623,280 discloses a passive applicator.

Induction system

The present invention also provides a system for guiding a vehicle or vehicle 222 traveling on a road 224 through a warehouse or the like, as generally shown in FIG. 12. Magnetic road marker 226 is attached to road surface 224 as described above. At this time, the array of magnetic road markers 226 may be detected by the sensor system 228 of the vehicle 222 traveling on the road surface 224. Typical sensor system 228 includes a sensor device and an induction device.

Multiple sensors and transducers can be used to convert the magnetic signals from the magnetic road markers of the present invention into electrical signals suitable for further processing. Examples of such sensors include flux-gate magnetometers, Hall effect sensors and solid state magnetoresistive sensors.

Potential problems exist in identifying induced signals from magnetic "noise" generated by steel reinforcement bars, other vehicles, and the like. When the magnetic road marker of the present invention is magnetized in a regular alternating pattern or some "unique" pattern, the magnetic signal becomes a periodic signal with a frequency proportional to the vehicle speed. Modern signal processing techniques can then be used to extract signals of known frequencies from noise.

The magnetic sensor 228 attached to the vehicle 222 may determine a magnetic field in one direction, two directions, or all three directions. A signal from one sensor or a mathematical combination of two or three magnetic field components can be used to calculate a signal related to the lateral distance of the vehicle 222 from the article of the present invention.

By magnetizing strips of more complex patterns, additional information can be encoded. For example, information about the direction and radius of the curve coming on the road or information about the slope of the approaching uphill or downhill road may be used for feedforward control of the lateral position and speed of the vehicle. As part of a vehicle navigation system, a location code may be provided. Examples of indicating means include at least one horn, gauge, whistle, electrical stimulus, LCD, CRT, light, combinations thereof, and the like. One or more indicating means may be desirable in certain situations.

Coherent Carrier Web

The integrity of the carrier web can be evaluated in several ways. One simple method is to manually press and remove a layer or sheet of material against a complex, rough, or woven surface, such as a concrete block or asphalt mixed road, and then measure the extent to which the surface roughness and shape are simulated in the layer or sheet. To observe. The conformable carrier webs of the present invention are matched to complex shapes and rough surfaces.

Elastic recovery is the propensity of a layer or sheet to recover to its original form after being deformed. Delayed elastic recovery can be observed by noting the propensity of the simulated roughness to disappear over time. A simple test for delayed elastic recovery is to indent the carrier web using a blunt instrument. The ease with which impregnation can be made and the permanence of the impregnation can be used to make a rough comparative judgment regarding the conformity of the materials used to form the sheet or layer.

The conformal carrier web of the present invention should be able to be deformed with an appropriate force to take good shape on the road surface by taking irregular shape of the road surface. By suitable force is meant the force by which the carrier web is mated to the road surface after the carrier is attached to the road surface and then rolled with a suitable force on the attached flat marking sheet with a suitable tamping means. In such applications, the tamped carrier web substantially mimics the surface texture of the roadway. Proper tamping means should not be overly difficult to handle. In the case of road marking tapes carried out in the prior art, tamping carts having a predetermined load (total weight about 250 lbs. (115 kg)) have generally been used for the attachment of marking tapes.

Other consistency tests may be available through the following sequence of steps. 1. About 30.5 in a tensile strength device until the test strip about 2.54 cm (1 inch) wide and about 10.16 cm (4 inch) long is tensioned to about 105% of the original sample length (elongation of about 0.51 cm). Pull (ie, deform or strain) at a speed of cm / min (12 inches / min). 2. Completely release the tensile stress of the sample by reversing the pull and returning the device to the starting point at a rate of about 30.5 cm / min. 3. Observe the strain at which resistance is first observed at the second pull (ie when the sample is strained again). The strain at which resistance is first observed at the second pull divided by the first strain is called inelastic strain (ID). In this example, the strain is measured by dividing the distance until the sample is tensioned by the original elongation of 0.51 cm. Perfect elastic material has an ID of 0%. That is, to its original length. The metal is close to 90% ID, but very undesirably results in high tensile stress. The force required to achieve 5% strain (i.e. strain) on the base sheet (typically an initial thickness of about 250 μm) is preferably less than 25 lbs. (44 Newtons / cm of sample width) per inch of sample width, More preferred is less than 10 lbs. Per inch (18 NT per cm).

Unload energy is also an important factor in determining the integrity of the carrier web for use in the present invention. Unload energy is defined as the energy remaining in the memory portion of the long material. Materials with lower unload energy will be more matched.

The conformal composition material of the present invention has a low unload energy of less than 1.25 g / cm (0.7 pounds / inch) and an ID of greater than about 10%, preferably greater than 20%, more preferably at least 30% at 25 ° C. To combine.

Example

Plane of the strip by passing multiple strips of Plastiform ™ magnetic tape 25.4 mm (1 inch) wide and 1.5 mm (0.060 inch) thick with pressure sensitive adhesive on one side protected by a separation liner through the gaps of the permanent magnets The strip was magnetized in a direction perpendicular to. Some of the strips were magnetized to the north pole on the uncoated side of the strip and some were magnetized to the north pole on the side coated with the adhesive. The strip was then cut longitudinally using scissors with a width of about 12.7 mm (0.5 inch), and then again with a Plastiform ™ chip of about 12.7 mm (0.5 inch) square on the adhesive and separation liner. Pieces of Reemay 2410 nonwovens in a 5-chip wide array with a separation liner removed from the chip and spaced about 6.35 mm (0.25 inch) between each square (available from Reemay, Old Hickory, Tennessee). A square was attached to. The array for this prototype was approximately 10.16 cm (4 inch) wide and approximately 22.86 cm (9 inch) long. About 15.24 cm (6 inches) of the array were placed with the north pole of the magnetic chip on top, and the remaining 7.62 cm (3 inches) with the north side down (ie, towards the membrane). The sheet was passed through a hand laminator to improve the adhesion between the pressure sensitive adhesive at the bottom of the magnetic chip and the membrane, thereby forming an array of magnetic elements interconnected by the carrier web (ie, the membrane).

A 0.127 mm (0.005 inch) thick layer of PM-7701 pressure sensitive adhesive (commercially available from 3M) was laminated to the bottom of the film on a separation liner (rubber resin pressure sensitive adhesive commonly used for road marking tape applications). Prototypes (or those without the PM7701 floor) may be useful for placing below the top surface of the road during its construction to provide magnetic signals. In addition, an array of magnetic chips may be mounted to the surface of the roadway. Nonwoven membranes or webs provide a low cost carrier for use in magnetic chips. The separation properties of the chips, rather than the continuous sheet, allow some chip movement relative to each other to conform to the roughness of the road surface, or, in the case of underlay installation, the movement during road compaction in an impossible way in a continuous sheet of coherent magnetic material. Allow. This feature also allows some movement to adapt to thermal expansion and thermal contraction and flexural stress on the road during use.

In this example, a polymer Plastiform ™ magnet was used. Ceramics, metals or other magnets may also be used. As an alternative to the Reemay membrane, other modified or alignable carrier webs or membranes can be used. The mating base sheet used in the road marking tape mating layer may be useful.

Some of the provided coherent mosaic magnetic road marking embodiments have magnetic south facing 4 rows of chips and magnetic strips having magnetic north facing 5 rows of chips northward from the plane of the sheet. Cut to the size of a 9 piece array. The separation liner was peeled off from the lower adhesive layer and the adhesive side of the article was laminated to the asphalt road and pressed in place by hand using a rubber roller. The individual magnetic pieces were relatively inconsistent with the roughness of the asphalt, but the sheet as a whole was adapted to conform to the surface roughness.

Magnaprobe (small, free-rotating bar magnet suspended on the ball mount-available from Cochranes of Oxford in Oxford, UK 85 Entref, Oxford, UK) over asphalt-coherent mosaic magnetic road markings I was. In the marking, the direction of orientation of the freely rotating magnet is reversed as it passes over a boundary that defines a change in the direction of the magnetic signal.

It will be apparent to those skilled in the art that many modifications may be made to the above-described embodiments without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the methods and structures described herein, but only by the methods and structures described by the claims and their equivalents.

Claims (20)

Forming an array of magnetic road elements joined together by a carrier web; Forming a breakable bond between the magnetic road element and a carrier web Method of producing a magnetic road marker comprising a. The method of claim 1, wherein forming an array of magnetic road elements mutually coupled by the carrier web comprises integrally forming the magnetic road element and the carrier web. The method of claim 1, wherein forming an array of magnetic road elements mutually coupled by the carrier web includes attaching the magnetic road elements to the carrier web. The method of claim 1, wherein forming an array of magnetic road elements mutually coupled by the carrier web comprises attaching the carrier web to an upper surface of the magnetic road element. The method of claim 1, wherein the magnetic road element comprises magnetic particles distributed in a binder. The method of claim 1, further comprising inducing alternating polarity along the array of magnetic road elements. The method of claim 1 further comprising applying a pressure sensitive adhesive to the back side of the magnetic road element, Attaching a separation liner over the pressure sensitive adhesive Method of producing a magnetic road marker further comprising. The method of claim 1, wherein forming the breakable bond includes at least partially cutting the carrier web around the perimeter of the magnetic road element. 2. The carrier web of claim 1 wherein the carrier web is selected from the group consisting of polymer film, paper, liner, screen, mat, nonwoven web, open scrim or a film or nonwoven web of a water soluble or aqueous dispersible polymer material. Method of making magnetic road markers. A method of attaching the array of magnetic road elements of claim 1 to a road surface, the method comprising: Interposing an adhesive between the magnetic road element and a road surface; Engaging the adhesive to the road surface under pressure How to include. 12. The method of claim 10, further comprising removing a portion of the carrier web between adjacent magnetic road elements to form an array of discrete magnetic road elements attached to the road surface. Forming an array of magnetic road elements in a predetermined pattern on the mating carrier web. 13. The method of claim 12, wherein the conformable carrier web comprises an extensible carrier web. A method of attaching the array of magnetic road elements of claim 12 to a road surface, the method comprising: Interposing an adhesive between the magnetic road element and a road surface; Engaging the adhesive to the road surface under pressure How to include. Magnetic road markers that can be attached to the road surface, An array of magnetic road elements joined together by a carrier web, Fractureable linkage between the magnetic road element and the carrier web Magnetic road marker provided with. The article of claim 15, wherein the carrier web and magnetic road element are integrally formed. The article of claim 15, wherein the magnetic road element is attached to a carrier web. The article of claim 15, wherein the carrier web is attached to the top surface of the magnetic road element. 16. The article of claim 15 further comprising a pressure sensitive adhesive applied to the back side of the magnetic road element and a separation liner extending over the pressure sensitive adhesive. 16. The article of claim 15, further comprising an adhesive interposed between the magnetic road element and the road surface.