Note: Descriptions are shown in the official language in which they were submitted.
This invention is concerned ~it~ improvements
in or relating to marking surfaces and is particularly
concerned with an improved apparatus for applying
marking materials to a road surface.
Various methods and means of applying marking
materials to surfaces such as highways and airport
runways are known. These include methods in which a
supply of the marking material is preheated to melt a
constituent of the material and is then applied to a
surface to be marked by passing through insulated pipes
to an applicator. This method suffers the drawback that
it involves a high capital outlay on the apparatus for
heating the marking material in buIk and maintaining it
at an appropriate temperature until it is applied. This
is usually done by employing two vehicles one carrying
the bulk supply of material and the other the applicator
apparatus, although one large vehicle may suffice.
Other methods are known, for example as
described in British patents 1,087,031 and 1,234,601 in
which the surface to be marked is preheated and the
marking material is then melted by contact with the
surface. Some preheating oE the material may take place
but the melting of the material takes place by contact
with the surface. This method again involves the use of
complicated apparatus and is also limited in the materials
which may be employed. The heat softenable constituent
of the marking material must be chosen with a sufficiently
low melting point to ensure that it is satisfactorily
melted by con~act with the preheated surface.
Devices for spraying particulate materials to
form coatings on substrates are also known and include
flame spray devices or apparatuses which are normally
used to apply coatings of refractory material and the
like.
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In such flame spray devices for example as
shown in British patent 1,109,481 it is usual for the
particulate material to be subjected to the direct efect
of a flame. This has the disadvantage that, where
materials with low melt temperatures are subjected to
the direct eEfect of the flame, great care has to be
taken to ensure the accuracy of the residence time of
such materials ln the flame if charring of the materials
is to be avoided. On the other hand, in arrangements
where high melt temperature materials are usbjected to
the heating effects of combustion gases there often has
to be some additional heat supply in order to achieve the
desired results. For example, in United Kingdom Patent
Specification Nos. 1,087,031 and 1,234,~01 pre-heating
of the highway surface to between 150F and 500F is
advocated.
The invention, as herein broadly claimed, pro-
vides an apparatus for applying to a road surface,
marking material which is fusible onto the surface, the
apparatus comprising means to burn a gaseous fuel in air
under pressure to provide a supply of heated pressurized
gas, duct means to direct the hot gas onto the road
surface to be marked and means to inject a supply of
marking material in unfused form into the hot gas stream -
within the duct means downstream of the burner means,thereby to cause the marking material to impinge on the
surface, characterized in that the duct means comprises
a first elongate mixing chamber portion down which the
hot gas is directed and into which the marking material
is injected and a second elongate outlet duct portion
co-axi~l with and downstream of the first portion, the
outlet duct portion being of rectangular cross-section
and having a ratio of length to maximum cross-sectional
dimension of at least ~.75:1 so that the distance of the
point of injection of the marking material from the road
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surface to be marked is such that at least some of the
markin~ material is fused before the marking material
impinges on the surface.
The outlet duct preferably includes a baffle
which extends longitudinally of the duct.
In one preferred embodiment, the injection means
for the marking material comprises a container for the
material~at least one supply line connecting the container
to the mixing chamber portion and means for supplying
compressed gas to the container to entrain the material
and carry it through the supply line.
Conveniently, the apparatus may comprise means
for supplying purging material under pressure to the
supply line to clear the supply line and duct.
The gaseous fuel may also be ignited, in a
preferred embodiment, in a flashback burner and burn
as it is passed through a combustion chamber, producing
a resultant stream of hot gas. The gaseous fuel may be
liquified petroleum gas.
The invention also includes a road marXing
vehicle comprising a self-propelled chassis and an
apparatus, as described above, having two ducts, and
associated with each duct a burner and a supply line,
both supply lines feeding from a common container and
in which the supply lines, burners and ducts are
rigidly mounted on the container such that one duct
faces the road surface on each side of the container.
The method applied for marking the surface
with a marking material may comprise, or provide at
elevated temperatures, a màterial which is fusible.
It may involve the steps of burning a gaseous fuel in
air under pressure to provide a supply of heated pres-
surized gas, directing this supply of gas onto the
surface to be marked,injecting a supply of marking
material in unfused form into the hot gas stream and
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thereby causing the matPrial to impinge on the su.rface,
and maintaining the temperature of the hot gas stream
and the distance of the point of injection of the
marking material from the surface throughout the
marking process such that at least some of the material
is fused before the marking material impinges on the
surface.
The material is preferably in particulate form
and may be fluidized before injection into the hot gas
stream. Preferably the marking material is injected into
the hot gas stream in a reducing atmosphere. The method
is particularly suitable for applying markings to highways
and runways and the like.
A preferred embodiment of the invention will now
be describedr by way of example, with reference to the
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Figure 1 is a side view of a vehicle fitted with the
apparatus for applying marking material o~ the present
invention~
Figure 2 is a plan view of the vehicle and apparatus
shown in Figure l;
Figure 3 is a diagrammatic representation of the spraylng : . :
apparatus;
..Figure 4 is a diagrammatic representation of an alt~rnative
appara~us incorporating a gravity feed arrangement or
}O. feeding part.iculate material; ; :
. Figure 5 and 6 each show front and side views of alternati~e
configurations of a flight tube for use in the.apparatus
. : I
of Figures 1 to 4 ,
Figure 7 shows twa views, side and plan, of a gas deflectox
-
for attachment to a flight tu~e of the~apptara~,w~
Figure 8 shows a~burner and swirl chamber in section; and
Figure 9 shows a further configuration of flight-tube wi~h a
: variable geomstryO
Apparatus us`ed hitherto, for the application of markings,
, ~ .
` to highways er airport runways, etc., has not always 'i
` resulted in a well defined-durable marking at an acceptable
speed~of application or an acceptable cost per unit area
- covered-by the markin~gO.
The apparatus shown in t~le drawings enables`-a layer
. : ; of a marking -material to be -sprayed onto ~a--high~
- - way, airvort ~ :runway or the liker wit~ great economy
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. in mat~rial usage, at low power consumption and with
minimum interruption of traffic flowO
Referring first to Figure 3, the apparatus comprises a
bulk storage hopper 10 from which particulate marking materizl
11 may be fed via a screw elevator 12 to a fluidised bed
feed device 14 and then via a line 16 to a mixing tube 18
where the material 11 is injected into a hot gaseous jet,
created b~ a buxner 20, before passing along a duct or
- fl~ght tube 22 to.be sprayed onto a hL~ghway 24, as shown
at 26, to form a marking on the highway 24. The material is
injected into a reduced atmosphere. The bulk storage hopper
10 is fed with compressed air from compressor 34 v1a a line
33 and control valve 31,so that the marking material 11
forms a fluidised bed. The hopper 10 can usefully have.a
. capacity of between one and six tonnes dependi~g upon the ~ -
size of vehicle on which the novel apparatus is to be-used.
The screw elevator 12 ideally has a feed rate of between
one and fifteen lit.res per minute and feeds the particulate
. marking.material via a duct 13 to the feed device 14. The
feed device 14 has a capacity for 200 kilos of the particulate
material fed thereto and comprises a container 30 fed with
compressed air to form a fluidised bed. The compressed air
is fed f~om compressor 34 via a line 33 and control valve
32 into the base of the container 30.
Material in the container 30 is ideally maintained at a
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level indicated b~ the dotted,line 35. A level switch 36, ,
provided on a side wall 37 of the contalner 30, is connected
to a motor 38 where~y rotation of the screw elevator 12 ls
e~fected in response to movement of a float member 39 ,
forming part of the valve 36. The feed device 14 also
comprises a venturi valve 40 connected to the line 16
inside the containc~ 30 which valve 40 is controlled by an
..
actuator ~1 whereby the rate o~ reed of particulate material
through the valve 40 may be adjusted or shut-off as requiredO
The actuator 41 is in turn conlrolled pneumatically, via a
solenoid controlled valve 42, from an appropriate control
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console 72 which may be mounted at any convenient location.
The disposition of the venturi valve 40 and the line 16
within the container 30 is consistent with obtaining a:
~, 15 flow of the particulate material which is of an acceptable
range o~ ~article sizes,i.e. the particulate material will
only show small diversities in size over a given period.
This is achieved by positioning the valve 40 and line 16
at an optimum le~el within the container. This occur~
20 because the'effect of the fluidised bed 14 is ~o strati~y ~ ,
-: :
, ~he particulate,material in the container 30 according to
, the~size of granule. Large granules,will ~e more prevalent
- towards the top of the co~tainer and small granules towards
the bot_om.' Thus, at an cpti~u~ level the ideal si~e
range of granule can he expected.
.
On the outlet ~ide or the line 16 between the container and
~he mi~in~ t~c 13 thc~e is shown a pigment feed hopper 44 1; -
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r~e ~ T-_ ~.n ~ lternative arrangement there may
.' .. L ~wo cr ~ore hoppers 44 and switching ,~f applopriate
v~ ri va.v~s loc~ted within the hoppe~_ 44 enahle~
thc des1red pi~ment to be fed into the flow of particulate
material in the line 16. There n~ay be spaced along line 16
c n~ber c~ annular passages for cool~ng the i_.
~ hc m;Ying tube 18, see Figure 3, is provided by a
tc~ .ar chambe-, 46 of circular cross section connected at
..n upper end portion 47, thereof to a combustion chamber 48.
~he: combustion chamber 48 is in turn connected to the outlet
9 of the burner 20, see Figure 8.
1~ c bu-ner ~0 may be a commercially available flash
back burner using liquid propane gas and air mi~ture as fuel.
~:,e ,_ir is su~plied via a line 52 fro~ the compressor 3a
and ~he ~as i~ supplied via lines 53 from liquid petroleum
5a_ stora~e tanks 54, see Figure 3. A s~ark generator 55 is
provided to initially ignite this fuel mixture.
The ~rran~ement is such that a mixture of air and
;:.(;..;c is coial-usted in th~ flash back burner 20 and the
~,~c; produced as a jet are prevented from oscillating
- t~ ~u~r hy passing the gaseous jet through the swirl chamber
4~ as showll in Figure 8~ This .cc~bustion cha~her oonsists of two
coa~ial cylindrical tubes 57 and 59. The inner tube 57 has
~ o rings of ports 58, which allow the air, fed via line 51
into the passage between tubes 57 and 59, to pass in~o tube
57 to react with a!'y unreacted fuelO These ports 58 are set
at. an angle, as shown, so as to introduce the air into tuhe
5/ wit.h a co~ponent of velocity in the direction of the
geneLal vt~locity OI the. gases already in the tube.
At the lower end portion 56 thereof the mixing
tube 1~ is connected to the flight tube 22 by a suitable
adaptor, not shown.
The length of the flifht tube 22 is chosen so that
the particulate material, which i.s admixed with the hot
gaseous jet in the mixing chamber 18, will remain in the
flight tube for a sufficient time for enabling suffici.ent
heat transfer from the gaseous jet to a heat softenable
portion of the particulate material to substantiall~ liquify
said portion.
In the arrangement shown diagrammatically in
Figure 3 the ratio of the lenght of the tube 22 to its
maximum cross-sectional dimention (width) is approximately
6.5:1. However, in other arrangements the tube 2~ may
have a length to width ratio of between 2:1 and 30:1. The
actual dimensions of the flight tube 22 will be chosen to
suit the application, the particulate material, the feed rate
of particulate material and the capacity of the burner 20.
Thus, in Figure 5 and 6 there are shown two further flight
~ 20 tubes 22a and 22b having length: width ratios of 9:1 and
4.75 1 respectively.
The flight tube 22 is also shaped to give a
lamella flow of particulate material therefrom. Thus; as
can clearly be seen from Figure 5 the tube 22a is rectangular
in cross-section and of constant dimensions along its length
while the tube 22b of Figure 6 is of variable cross~section
along its length, being approximately square at its upper
end and tapered in one dimension and flared in the other
; from that
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end to its lo~le~- end. The xectangular shape of the outlet
end o4 the flight tube helps to ensure that markings
applied by the apparatus do not have blurred edges.
~ In the arrangement shown in Figure 3 the flight tube 22
is of constant dimension along it5 length and no yreat
difSiculty is encountered in obtaininy a true lamella
flow of 2naterial from a noæzle end 25 thereof. However,
with some lengths of tube conditions may arise in which
, the gaseous jet and admixed particulate material o~cillate
wl.hin the tube leading to accretion of the particulate
material to the side walls of the flight tube 22.
In order to prevent the occurrence of unwanted oscillations
and the consequent accretion of the particulate material
to the side walls of the flight tube 22, baffle plate~
may be provided down the centre of the flight tube 22
to spli~ the tube in two length-wise. Indeed several
bzffles may be provided splitting the flight tube along
~ts lenyth into several parts. Tests on such arrangements
h~ve shown that the resultan markings are not impaired
in an~ ~ay whlle accretion of material to side walls o~
th~ flight tubes 22 is p~ever.tedO
- It i-s also envisaged that use may be made of alternatiue
methods of preventing unwanted oscillation of the mate~Lal
- in the flight tube. ~Such a-lternative methods mav include~-
-~he use of annul~r i~let ducts for introducing hot g~ to ~e tlbe ~2-
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to augment ~e flow of the gaseous ~et therethrough.
~ccxetion is also prevented by lining the flight tube with a
perforated lining plate, which also has the advantage
of reducing the noise of the operation.
In the arrangem~nt shown in Figure 3 only one line 16
' ~s shown connecting with the mixing ch~mber 18; however
two o~ more such lines may be connected to the chamber
18l see Flgurc 4. In addition it ~s envisaged that,
while the lines 16 are arranyed at an acute angle of 35
: to a longltudinal axis of the mixing chamber 18, in the
embodiments illustrated, a~y convenient angle of entry
m~y b~ used. In addition the entry ports need not be
diametrically opposite one another, as shown in Figure
4, but mav be staggered along the length of the mixing
chamber 18.
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The apparatus may also include purging means for
purging the apparatus of particulate material at the end of
work shift. This purging means may comprise a container
~0 for cleaning grit, sand, or the like material~ This
ma erial may be fed into the feed device 14 via a venturi
valve similar to valve 400
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Thus, air rrom the compressor wiLl cause cleansing
~, material to ~e fed to the mixing chambers 18 as aforesaid,
via the valve 40 and line 16 to purge the mixing chamber
18 and flight tube 22 of any residual particulate material.
The purging means may also comprise a fluiclised bed
for agitating the sand in the container.
It is often desired to spray a material s~ch as small
glass beads onto the road 24 to form a top re1ective layer
of the marking 26, These beads are h~ld in a
hopper 60, and may be agitated ~o form a fluidised bed. To
feed these beads to the road they are passed down a tube 61
and through a pneumatically controlled venturi valve 63
onto the road 24.
The apparatus described above may be adapted for
mounting on a vehicle 80, see Figure 1 and 2, which vehicle
is of much simpler design than known road marking vehicles.
In the arrangement shown in Figures 1 and 2, there is
a l~terally moving carriage 81. This carriage includes a
feed means 14, and a hopper 60 to hold glass beads and the
like. There are also two sets of flight-tube 22, mixing
chamber 18, feed line 16, o~bustion chamber 48 and burner 20
one set at each end of unit 81 and thus one set on either
side of the vehicle 80. In addition there are two tubes
61 running from hopper 60 r one tube disposed behind each
flight-tube 22.
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37~L
As an alternative, there may only be one set of
flight-tulbe, mixing chamber, feed line, ccmbustion chan~ber and
burner, all of which may be mounted as a boom to swing to
either side of the vehicle. This boom may be covered by a
thermally insulating jacket to protect operative personnel
from burns.
Although the apparatus described hitherto is provided
with a fluidis~d bed feed means it may be useful in
some applications to utili~e a gravity feed arrange-
ment as shown in Figure 4. The particulate material
r, can thus be fed to the line 16 via a line 84 and a
venturi valve 85 of known configuration.
In a further modified apparatus (see Figure 7) a gas
deflector 86 may be attached to the lower end portion
25 of the flight tube 22. This arrangement is utilisedto assist the adhesion and settiny of the sprayed on
marking 26.
The apparatus described above has several major advant-
ages in determining suitable marking materials which
it may utilise.
In the conventional thermoplastic road marking materials,
- the binder resins must melt to a state of high fluidity
to enable the overall composition to be sprayed or flowed
(screeded or extruded) onto the road surface. This
limits the types of resin, or polymer, which can be used,
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and also effectively lirnits the final performance of
the road marking material. High fluidity results from
relatively low molecular weiyht which in turn leads
to low mechanical strength and touc~hness.
The materials capable of being used by the above apparatus
do not have this limitation, in that it is apparently
sufficient that individual binder particules should
melt in order to adhereto the surrounding particles of
filler, pigment, beads, etc. Thus binder polymers can
be chosen of much higher molecular weight which give
enhanced mechnical propert es over existing thermoplastic
composit'ons.
.
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The individual components of the materials used do not
need to be thoroughly compounded before application. Thus,
a simple blend of polymer powder, pigment, aggregate and
glass beads providing it is mixed uniformly before use,
~ apparently gives an homogeneous coating to substrates.
The apparatus is suitable no-t only for the use of thermo-
plastic materials, but also for thermo-setting materials.
A typical thermo-setting type would be an epoxy powder
coating material which comprises an intimate blend of
an epoxy compound and a reactant, which do not effectively
2~
react to give a polymer until a threshold tempera-ture
above 100 is reached. If used in the above apparatus,
such particles would melt to fuse into a coherent
whole and a chemical reaction would occur to improve
the mechanical properties still further.
A composition, particularly suitable for use in the
apparatus described above to provide markings on highways
; or airport runways, etc., is one such as described in
~ our ~atent Speci~ica~ion WoO1344255 e ~titled "Improvements
Relating to ~oad marking."
Although -uch a material is described as particulate~
material in other forms may also be used in the apparatus
e.g. particulate materials in a liquid suspension are
envisaged.
lS The vehicle 80, may incorporate any convenient sighting
or sensing device for alignment of the flight tube 22
of the spraying apparatus over the portion of the highway
24 to be marked.
The vehicle 80 is driven along the highway 24 and a marking
2~ applied thereto. The thickness of the marking may
be in the range 0.3 - 4.0 n~and is prefPrably in the
range 0.5 - l.S mm.
The operation of the apparatus may be automatic in response
of sensing of areas to be marked or the apparatus may be
3~
controlled manually from the console 42 by the vehicle
driver. In either case the on-off cycle may be achieved
~! by opening and closing the venturi valve 40 of the feed
device 1~ to interrupt the feed of the particulate material.
In shoxt line markings interruption of the burner operation
is not necessar~; however, in long line markings where
long gaps are formed between the markings it is economical
to shut off the burner 20.
The end of line definition is remarkably clear and no
ghosting in the gaps between markings is evident.
The high impact velocity of the marking material on
the road surface improves i-ts adhesion.
In addition almost perfect resolution and material
~5---distribution is~ achieved with the spraying apparatus.
In use, the burner 20 creates a hot gaseous jet in a
reducing atnos~ere capable of raising the ternperature
of the particulate material without charriny to above
its melt temperature which, according to the heat softenable
portion of the particulate material used, will be 100
to 430 C. The heat generated by the burner 20 must
therefore be in the order of 1 M BT~s per hour in order
to provide sufficient latent heat in the hot gaseous jet
to enaDle it to affect the particulate materials as
aforesaid.
Other advantages of usiny the apparatus described above
to carry out the met}lod of spraying particulate material
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are:
(i) low cost compared with presently available line
spraying equipment;
(ii) operation as a continuous process by one man using
a single vehicle;
(iii) short warm up periods for operation conditions to
be reached;
(iv) low pigment level requirement;
~v) instantaneous colour change where hoppers 44
and venturî valvec are utilised;
(vi) lower fuel consumption compared with known
arrangements;
(vii) less environmental pollution;
-(viii) less hazard to operatives- from easily shielded
applicator assembly;
(ix) no hot materials to handle or maintain in
liquified condition;
(x) temperature sensitive materials may be used
because o~ short duration at high temperature.
20 In the arrangement described a flashback burner is used
to create the gaseous jet. In alternative arrangements
a gas turbine or free piston gas generator may be used.
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Further modifications may also be made to the apparatus
~'15! with the scope of the invention. For example, a variable
geometry flight tube as shown in Figure 9 might be employed
rather than the fixed flight tubes described above in order
5 to adjust the width of markings and form symbols such as
arrows. Furthermore, the ingredients of the marking
material need not all be injected into the flight tube at
the same point and the aggregate, for example, could be
injected upstream of the burner.
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