Method and apparatus for painting road surfaces

A method and apparatus for painting highway stripes and other patterns on a road surface includes the steps of heating the road surface to be painted or treated with a protective coating to a temperature typically in the range of 150.degree. F. to 165.degree. F. Paint is applied in spray form, the resin and hardener ingredients being mixed preparatory to spraying by a spray head. The paint mixture is sprayed onto the heated road surface as soon after the heat treatment as is practical. The paint spray may be heated as it passes through the nozzle. Granulated glass beads may be dropped onto the paint coating to enhance absorption of heat energy by the paint. The spraying operation is followed as soon as practical by a post-heating operation which preferably achieves temperatures in the aforesaid range, the pre- and post-heating operations significantly enhancing the cross-linking and drying of the paint or other coating enabling substantially immediate use of the road surface by vehicular and/or pedestrian traffic. The energy levels and the heating units and their spacing from the road surface are adjusted to heat the road surface (and paint) to the desired temperature.

FIELD OF THE INVENTION 
The present invention relates to painting of road surfaces and the like and 
more particularly to the utilization of pre- and/or post-heating of the 
road surface being painted to enhance cross-linking and drying of the 
paint ingredients and thereby significantly reduce the overall costs 
normally encountered in conventional painting operations. 
BACKGROUND OF THE INVENTION 
Road surfaces such as concrete, asphalt, macadam surfaces and the like 
utilized for interstate, major and even rural roadways are customarily 
provided with painted stripes and other patterns and indicia which serve 
as lane indicators, roadway edges, pedestrian crosswalk indicators and the 
like. 
These patterns, stripes and the like, in addition to being initially 
provided on road surfaces, must also be replaced from time to time due to 
their constant wearing by both vehicular and pedestrian traffic as well as 
erosion caused by natural elements (i.e. wind, rain, snow, constant 
temperature changes, etc.). 
The conventional method for providing such road surface markings includes 
setting down temporary, typically portable traffic detouring devices 
arranged at spaced distances along a road surface and in such a manner as 
to indicate to vehicular traffic that a road surface or portions thereof 
are temporarily closed and that traffic is being detoured therearound to 
permit the painting operation to be performed safely and without 
interference with vehicular traffic. Although painting operations may be 
scheduled during periods of low traffic volume, traffic congestion can 
hardly be avoided. 
Once the highway detour markers (i.e. cones) are in place, markings are 
provided to identify the stripe or other pattern to be painted onto the 
road surface. This operation is typically performed by a vehicle having 
apparatus thereon for placing the markings on the road surface, which 
markings act as guides for the painting operation which follows the laying 
down of the guide markings. The vehicles employed for the laying down of 
the guide markings and the paint operation are typically separate 
vehicles. 
The painting operation is preferably performed utilizing mechanized 
apparatus arranged upon a vehicle, which is fitted with equipment capable 
of detecting the guide markers and positioning the spray equipment to 
follow the guide markers and thereby accurately place the spray pattern at 
the desired location upon the road surface. 
The paint is typically allowed to dry for before the roadway is reopened to 
vehicular traffic in order to prevent the painted markings from being 
lifted onto the tires of vehicles and thereby be "reprinted" upon the road 
surface thus deteriorating and significantly reducing the effectiveness 
and the useful life of the painted markings. The paints presently 
developed for use in painting road surfaces and having superior wear 
properties require longer drying times, typically 25 to 30 minutes and are 
thus more expensive to use and apply. 
The conventional techniques utilized for reducing drying time include 
limiting performance of the painting operation to the summer months or at 
the minimum, and typically to clear, dry days at those times of the year 
during which warmer temperatures are encountered. In addition, the paint 
ingredients may be heated as they are mixed preparatory to being sprayed, 
which technique somewhat promotes cross-linkage and drying of the paint 
ingredients. 
Nevertheless, even when the above techniques are employed the paint 
requires at least 20-30 minutes to dry. 
The cones placed on the road surface are removed from the road surface 
after the paint has dried, enabling the roadway to be returned to normal 
usage. 
The conventional methods described above are very highly labor intensive 
adding significantly to the cost of the operation. The time required to 
perform all of the steps involved in the painting operation results in a 
significant contribution to the amount of inconvenience and congestion 
experienced by vehicular and/or pedestrian traffic over the period of time 
during which the roadway or portions thereof are closed to such traffic 
which further contributes to the need for improved and effective painting 
techniques in order to reduce traffic congestion as well as costs. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention is characterized by comprising method and apparatus 
for coating road surfaces which significantly reduces capital equipment 
and labor costs as well as significantly reducing the paint drying time 
which results in a direct and significant reduction in the amount of 
congestion and inconvenience occurring over the period of the painting 
operation, which method and apparatus includes the use of pre- and 
post-heating steps which serve to significantly reduce drying time and to 
totally eliminate the traditional steps of placing and removing roadway 
detour devices which procedural steps are required when utilizing 
conventional painting methods. 
The pre-heating step is performed by providing one or more heating units 
for generating radiant energy for performing the pre- and/or post-heating 
operations. The heating units are preferably of the type capable of 
generating radiant energy in the infrared and red wavelength bands. One or 
more such units are mounted upon a self-propelled vehicle or a vehicle 
such as a trailer capable of being pulled by a self-propelled vehicle. The 
heating units are preferably movably mounted upon the vehicle so as to be 
positioned or positionable in relatively close proximity to the road 
surface to be painted and so as to direct radiant energy toward at least 
the portion of the road surface to be heated. The radiant energy devices, 
in a preferred embodiment, are gas burning units, generating radiant 
energy in the infrared and red bands, which energy is capable of 
penetrating into the surface of the roadway so as to elevate the roadway 
surface to a temperature sufficient to significantly increase 
cross-linking of the paint ingredients, and hence the drying of the paint. 
The radiant energy is derived from heating devices preferably comprising a 
ceramic fiber matrix supplied with a gas which is burned at the matrix 
surface, which heats and re-radiates energy in the infrared and red bands 
toward the road surface. 
The heater units are preferably mounted upon a vehicle or trailer pulled by 
a vehicle, and are arranged in close proximity to the road surface during 
heating. The plurality of heating units may be mounted in a tandem array 
to increase the amount of heat according to local conditions. Separate 
arrays may be provided along opposite longitudinal sides of the vehicle to 
permit heating of a pair of parallel surfaces substantially 
simultaneously. 
A microprocessor-based controller, which derives temperature readings of 
the road surface and/or ambient temperature, controls the heat energy 
directed to the road surface by controlling: spacing distance of the 
heating units from the road surface; proportionality of the gas mixture; 
flow rate of the gas mixture to the heating units and controlling the 
number of tandem units utilized for preheating; and vehicle speed. 
The painting operation preferably immediately follows the preheating 
operation in order to obtain the greatest benefit from the heated road 
surface, which significantly enhances the cross-linking of the paint 
ingredients and drying of the paint. The painting apparatus is thus 
preferably mounted upon either the same vehicle or a trailer or other 
vehicle linked to the wheeled unit carrying the heating apparatus. The 
paint ingredients, typically a resin and a hardener, are mixed preparatory 
to being sprayed from a nozzle, and may also be heated during or just 
prior to mixing to further enhance drying of the paint. 
Preheating of the road surface significantly enhances the drying rate of 
the paint. 
Since the earth typically serves as a heat sink for drawing heat away from 
the heated road surface, a post-heating operation is utilized to prevent 
retardation of the drying operation due to the chilling effect of the road 
surface, which loses the heat applied thereto rather rapidly. 
To assure the objective of rapid drying of the paint, a post-heating 
operation is performed utilizing substantially the same equipment utilized 
during preheating, which equipment preferably closely follows the paint 
applying apparatus by a short a distance as is practical. The post-heating 
apparatus may be part of the same vehicle supporting the preheating and 
painting apparatus or may be mounted upon a separate vehicle or trailer 
following the main vehicle and linked to and being towed by the vehicle 
supporting the preheating and painting apparatus. Alternatively, the 
heating units may be mounted upon a separate vehicle which closely follows 
the apparatus performing the spraying operation. 
The post-heating apparatus is preferably of the same type as the preheating 
apparatus, and is controlled in a similar manner to increase the 
temperature level of the paint and supporting subsurface to a level 
similar to that obtained during the heating step. 
The heating units may also be employed to remove unwanted paint. 
OBJECTS OF THE INVENTION 
It is therefore one object of the present invention to provide a novel 
method and apparatus for applying and drying paint on road surfaces and 
the like in an efficient and cost effective manner. 
Still another object of the present invention is to provide novel method 
and apparatus for painting road surfaces and the like and which utilizes a 
pre-heating operation preparatory to painting. 
Still another object of the present invention is to provide novel method 
and apparatus for painting road surfaces and the like utilizing a 
post-heating operation after painting to achieve a more efficient and cost 
effective painting operation. 
Still another object of the present invention is to provide a novel method 
and apparatus for painting road surfaces and the like and which utilizes 
pre-heating and post-heating operations respectively before and after the 
painting operation to significantly enhance the cross-linking of the paint 
ingredients and drying of the paint and thereby yielding a more efficient, 
and cost effective technique which eliminates a significant amount of 
labor intensive activity required when utilizing conventional painting 
techniques. 
Still another object of the present invention is to provide novel means for 
controlling pre- and/or post-heating apparatus for heating road surfaces 
and the like to an elevated temperature within a predetermined range 
thereby significantly enhancing the drying of a coating applied to the 
road surface. 
Still another object of the present invention is to provide novel heating 
apparatus and control means therefore for removing unwanted paint and the 
like from road surfaces.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF 
FIG. 1 shows apparatus 10 employed for performing the method of the present 
invention and being comprised of a transport vehicle 12 which is 
preferably a truck or other suitable self-propelled vehicle comprised, for 
example, of a truck cab 12a and a truck bed 12b supported between the 
front 12c and rear wheels 12d and in turn supporting a plurality of gas 
fired infrared heater units 14. 
Units 14 are supplied with a suitable combustible gas such as LPG or an 
equivalent thereto which is stored within holding tank 16. 
An extension and retrieval mechanism 18 is mounted upon truck bed 12b and 
controls the lifting and lowering of pairs of telescoping support 
assemblies 18a, 18b and 18c each of which support a heating device and 
further incorporate a conduit (not shown) for supplying gas from tank 16 
to the heater units. 
Controls 20 are mounted at the rear of bed 12b and provide means for 
controlling the rate of gas flow, the gas mixture (such as a 
proportionality of air and gas in an air-gas mixture), the number of 
heater units operated and the spacing distance of the heater units from 
road surface S to be painted with a paint strip P. 
FIG. 1a shows a modified arrangement in which like elements are designated 
by like numerals and wherein an apparatus 10' is utilized to perform a 
painting operation which includes apparatus for pre-heating, painting and 
post-heating a road surface. The truck 12' in FIG. 1a differs from that 
of FIG. 1 in that the truck bed 12b' is elongated to accommodate painting 
apparatus 22 together with the pre-heating apparatus comprised of units 
14, 16, 18 and 20. 
The painting apparatus 22 is comprised of storage tanks 24 and 26 for 
storing the paint (or other coating) constituents, such as a resin and a 
binder, together with control means 28 for proportionally feeding the 
paint constituents to a spray head 30 and which includes means 32 for 
heating the constituents of the paint as they are admixed preparatory to 
being sprayed upon a road surface by spray head 30. The spraying equipment 
utilized in the present invention may be comprised of conventional 
spraying equipment such as, for example, a vehicle on which a driver 
observes the markers or previous stripe to position a spray head or on 
which an operator positions a movable boom carrying a spray head by 
observing a video image of a road surface. 
The paint which is sprayed on the road surface may, for example, be 
two-part epoxy paints which exhibit improved weather resistance, UV 
stability and/or high reflectivity. Epoxy paints, while more expensive, 
are more commonly used on federal highways. 
Alternatively, latex paints which contain reflective materials may also be 
used with the methods of the present invention. 
It should be noted that spraying equipment and paint having characteristics 
similar to those set forth above may be substituted therefor. Also any 
other coatings, protective or otherwise, and which require a long drying 
period may be dried using the techniques disclosed herein. 
A wheeled trailer or low-boy 34 may be coupled to vehicle 12' by suitable 
linkage assembly 36. Trailer 34 supports an extension and retrieval 
apparatus 18 substantially identical to that mounted on truck bed 12b' for 
supporting heating units 14 and for lifting and lowering units 14 through 
mechanisms 18d and 18e similar to the mechanisms 18a through 18c of FIG. 
1. Although the embodiment of FIG. 1a shows a reduced number of heating 
units provided, the actual number employed is dependent upon the 
particular application and may be a number which is greater or lesser than 
the number of units shown. 
The post-heating apparatus on trailer 34 may be supplied with combustible 
gas (such as LPG) derived from the common tank 16 and be controlled by the 
controller 20 provided on truck bed 12b' or, alternatively, may be 
provided with its own supply tank 16' and controller 20', shown in dotted 
fashion and mounted upon trailer 34. 
FIG. 2 shows the controller 20 in greater detail. The simplified block 
diagram of FIG. 2 shows controller 20 which is comprised of a central 
processing unit (CPU) which incorporates a microprocessor, a ROM for 
storing operating programs and a RAM of a capacity sufficient to accept 
input data and carry out controls and other functions in real time. The 
CPU senses road surface temperature by a first sensor 42 which may, for 
example, be an infrared sensor. The second temperature sensor 44 is 
utilized to sense ambient temperature which readings may be combined with 
sensor 42 to control the heating units 14. 
A proximity sensor 46 measures the distance between the heating units 14 
and the road surface. In instances where all of the heating units are 
simultaneously controlled to be moved to the same elevation above a road 
surface, it is necessary to provide only one proximity sensor per group of 
heating units for the pre- and post-heating apparatus. Alternatively, in 
applications where each heating unit is capable of being positioned 
relative to the road surface independently of one another, a proximity 
sensor may be provided for each heating unit. 
The CPU 40 controls the various controllable means responsive to the sensed 
conditions. For example, given the road and ambient temperatures, CPU 40 
controls the raising and lowering of each of the units 18a through 18c 
(or 18 through 18e) by means of control 48. The flow rate of the 
combustible gas is regulated by suitable valve means controlled by the 
flow rate controller 50, which valve means may form part of the spray 
assembly 30. Pressure control means may be provided either as an 
alternative or in addition to the valve control means. The number of 
heater units operated during a heating operation can also be controlled in 
this manner. 
Heater unit ignition is controlled by the ignition control circuit 52 which 
provides ignition of the desired heater units 14 and/or re-ignition in the 
event that there is a flame-out which may be detected by suitable 
flame-out sensor means, not shown for purposes of simplicity. 
The temperature to which the road surface is elevated may further be 
controlled by controlling the dwell time of each heater unit per unit 
surface area of the road surface being heated. The dwell time may be 
controlled by controlling the speed of the vehicle through speed control 
54. A speed sensor 56 senses the present speed of the vehicle which is 
compared in the speed control 54 with the desired speed to effect the 
appropriate adjustment in vehicle speed. 
The heating units may be of any type conventionally available for providing 
radiant heat energy in the infrared and red wavelength bands. For example, 
the radiant heaters, in one preferred embodiment, are comprised of a gas 
fired radiant heater having a porous refractory panel through which a 
combustion mixture is passed. The combustion gas is ignited and burns at 
the surface of the panel which absorbs and/or reflects heat from the 
burning gas and reradiates the heat energy, especially in the infrared and 
red wavelength bands, toward a road surface. The porous panel can be flat, 
convex, concave or have any other desired configuration. Panels having a 
concave burning surface serve to focus and concentrate the heat energy. 
The panels can and preferably do have a width greater than the width of 
the strip or other pattern to be painted. The panels may be positioned so 
that there is a relatively small gap space G between adjacent edges, as 
shown in FIG. 1. 
Although not shown for purposes of simplicity, heating units 14 may be 
placed on opposite longitudinal sides of the truck bed 12b enabling the 
heating of two "stripe-shaped" elongated regions of a road surface and, by 
providing spray units 30 on opposite longitudinal sides, two stripes may 
be painted substantially simultaneously immediately following the 
pre-heating operations. 
The heating units described hereinabove may be of the type described in 
U.S. Pat. Nos. 3,785,763; 3,824,064; and 4,035,132, although any other 
type of radiant heater unit capable of generating radiant energy in the 
infrared and red wavelength bands may be utilized. For example, gas fired 
metallic and/or ceramic radiant heaters may be employed. Alternatively, 
electrically powered radiant heaters may be employed so long as they are 
capable of meeting the requirements of elevating the temperature of the 
road surface to a level which lies within a range that provides the 
significant improvement in the drying period described above. 
To date, our experimentation has shown that elevating a road surface to 
temperatures of 150.degree. F. or greater provide a significant reduction 
in the drying period, i.e. result in a quantum jump in reduced drying time 
as compared with standard drying period. 
The heating units utilized are capable of providing infrared and red band 
radiation at temperatures in the range of from 950.degree. to 1100.degree. 
F. or more. Notwithstanding this temperature range, units of the type 
described are capable of being operated at temperatures of as much as 
1500.degree. or higher. 
As was described hereinabove, the heating units 14 are arranged in tandem 
and are controlled to generate predetermined heat levels according to the 
road surface and/or ambient temperatures, further regulation being 
obtained by controlling the gas mixture (i.e. air/gas ratio) and spacing 
distance between the heating units and the road surface and the number of 
heating units ignited as well as controlling vehicle speed. 
Vehicle operating speed normally employed when performing conventional 
painting operations is typically between 6 and 13 miles per hour and 
preferably between 6 and 9 miles per hour. Given the ambient weather and 
temperature conditions, lower speeds may be utilized, if desired. 
Using conventional techniques, the "time window" available to paint road 
surfaces is rather narrow, painting operations typically being performed 
during the summer months and on clear, dry days when road surfaces are 
typically warmer than usual. Use of the techniques of the present 
invention significantly broadens the "time window" and, in addition, need 
not be confined to use on only dry, sunny days. 
As was previously mentioned hereinabove, elevating the temperature of the 
admixed paint ingredients preparatory to spraying lowers the viscosity of 
the mixture, thus facilitating the spraying operation. The paint will 
nevertheless chill rapidly when applied to an unheated road surface thus 
significantly retarding the cross-linking and drying process. By raising 
the temperature level of the road surface during a preheating step to a 
temperature of 150.degree. F. or greater significantly contributes to the 
drying process, reducing drying time to a small fraction of the time 
required when utilizing conventional techniques. Conventional air drying 
usually requires 20 to 30 minutes before vehicles are permitted to return 
to the roadway or those portions thereof which have been painted. The 
pre-heating operation, used alone, results in a 50% reduction in the 
drying period as compared with conventional drying, enabling vehicular 
traffic to use the treated road surface almost as soon as the equipment 
leaves the painted road surface. 
It is preferred that the road surface not be heated to a temperature level 
which will cause discoloration and/or charring or burning of the paint. 
Using paints conventionally employed for painting road surfaces, the upper 
temperature is of the order of 165.degree. F. However, the upper end of 
the temperature range may vary somewhat dependent upon the particular 
paint composition being utilized, the upper temperature range being 
determined in a straightforward manner. 
The infrared band and red band radiation energy applied prior to the 
spraying operation and by the road surface is absorbed by the paint as it 
is deposited thereon. If desired, absorption of the energy by the paint 
can be enhanced by sprinkling granulated glass beads upon the freshly 
painted surface. The glass beads enhance the absorption of energy into the 
paint. 
The post-heating step is utilized to ensure a final cure since cooling of 
the road surface and the paint starts as soon as the paint hits the road 
surface. Paints which are elevated in temperature just prior to spraying 
are typically elevated to a level of 140.degree. F. This absorbed heat is 
dissipated quite rapidly in the absence of the pre-heating step. 
The road surface is preferably elevated to the same temperature during the 
post-heating operation as is employed during the pre-heating operation. 
However, less heating energy typically is required during the post-heating 
operation since the road surface and paint retain some of the heat that 
has been absorbed due to the pre-heating step. The radian energy 
penetrates the paint and the road surface to enhance drying of the paint. 
Radiant energy in the region of 2.1 microns (which lies within the above 
mentioned wavelength bands) is employed to obtain the desired penetration 
of the radiant energy into the paint and road surface. 
Use of both the pre- and post-heating operations respectively before and 
after spraying reduces the drying period to two (2) minutes or less 
thereby totally eliminating the need for setting up cones on the highway 
preparatory to the painting operation and, thereafter, the need for 
removing the highway cones 20 to 25 minutes after the spraying operation 
is completed. The elimination of these highly labor intensive operations 
significantly reduce painting costs in addition to significantly reducing 
the time interval during which vehicular traffic must depart from its 
normal flow rate and thus the amount of congestion caused thereby is 
likewise significantly reduced. The simplified process provides a more 
efficient use of man-hours and resources resulting in reduced operating 
costs. 
The active heating system also allows a longer working season which 
ultimately leads to increased throughput per year resulting in increased 
gross revenue for equivalent capital equipment investment. 
The apparatus utilized to paint continuous or broken lines, stripes or 
other patterns may utilize markers which are initially set up to identify 
the locations where the lines or patterns are to be formed, which markers 
may take the form of an asphalt or concrete seam in the case of new or 
resurfaced roads. In the case of re-striping applications, the paint coats 
the existing stripe or partially ground stripe. 
In either case the driver of the truck steers the vehicle by watching a 
video monitor which displays the spray gun's target. 
A boom operator may also "steer" the boom upon which the spray head is 
mounted onto the proper location. These techniques may also be applied to 
position the pre- and post-heating units which are detected by sensors to 
accurately position the spray heads at the desired locations. 
The painting equipment and specifically the spray head (or heads) are 
mounted so as to be movable in a direction transverse to the direction of 
movement of the vehicle and sensors are provided to detect the markers and 
thereby spray paint onto the road surface at the desired locations, all of 
which techniques are conventional. The pre- and post-heating units may 
likewise be mounted on transversely movable supports and be positioned 
therealong by either the same equipment or equipment similar to that 
utilized for positioning the spray heads. 
A further application for the heating units would be to aid in the removal 
of existing stripes. This is generally accomplished by over-curing the 
paint. This ultimately causes the existing stripe to lose adhesion with 
the road surface. The reduced adhesion permits a more efficient use of 
surface grinding to remove the paint chips. 
This method also helps preserve the integrity of the road surface by 
reducing the mechanical contact of the grinder with the road surface. 
Typically, surface temperatures in excess of 200.degree. F. with two (2) 
minute dwell times are required to sufficiently affect (i.e. degrade) the 
adhesion properties. 
A latitude of modification, change and substitution is intended in the 
foregoing disclosure, and in some instances, some features of the 
invention will be employed without a corresponding use of other features. 
Accordingly, it is appropriate that the appended claims be construed 
broadly and in a manner consistent with the spirit and scope of the 
invention herein described.