US3477352A

US3477352A - Self-propelled apparatus for applying markings to roads and the like

Info

Publication number: US3477352A
Application number: US692515A
Authority: US
Inventors: John Harding; Peter Placzek; Sidney Glenroy Campbell
Original assignee: UNIVERSAL HIGHWAY CONTRACTING
Current assignee: REDLAND PRISMO Corp; REDLAND PRISMO Ltd; UNIVERSAL HIGHWAY CONTRACTING; UNIVERSAL HIGHWAY CONTRACTING Ltd
Priority date: 1966-12-28
Filing date: 1967-12-21
Publication date: 1969-11-11
Anticipated expiration: 1986-11-11
Also published as: NO122486B; DE1658551A1; SE345886B; BE708549A; GB1211690A; CH488059A; AT288472B

Description

SELF-PROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKE Nov. 11, 1969 J- HARDING ET AL 3,477,352

1969 J. HARDING ET AL 3,477,352

' SELFPROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKE Filed Dec. 21, 1967 5 Sheets-Sheet 2 Nov. 11, 1969 J.-HARDING ET AL 3,477,352

SELF'PROPELLED APPARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKE Filed Dec. 21, 1967 N ,1969 J. HARDING ET AL 3,477,352 SELF-PROPELLED APPARATUS FOR APPLYING MARKINGS T0 ROADS AND THE LIKE 5 Sheets-Sheet 4 Filed Dec. 21, 1967 I Nov. 11, 1969 v J. mm; ETAL 3,477,352

SELF-PROPELL ARATUS FOR APPLYING MARKINGS TO ROADS AND THE LIKE Filed Dec. 21, 1967 v 5 Sheets-Sheet 5 United States Patent 3,477,352 SELF-PROPELLED APPARATUS FOR APPLYING MARKINGS T0 ROADS AND THE LIKE John Harding, Peter Placzek, and Sidney Glenroy Campbell, Rowfant, near Crawley, England, assignors to Universal Highway (Contracting) Limited, Rowfant, near Crawley, England Filed Dec. 21, 1967, Ser. No. 692,515 Claims priority, application Great Britain, Dec. 28, 1966,

7,982/66 Int. Cl. B05b 7/16, 9/06 US. Cl. 94-44 11 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method of applying markings in the form of continuous or discontinuous lines on the surfaces of roads or the like and is also concerned with self-propelled roadmarking apparatus for use in carrying out this method.

The invention has for its object to enable such markings to be applied along a road surface or the like at speeds of up to miles per hour.

According to the invention a road-marking apparatus includes a vehicle having mounted thereon a spray gun arranged for spraying a molten thermoplastic road-marking material onto a road surface beneath the vehicle to form a coating thereon in the form of a strip, means for storing the thermoplastic road-marking material on the vehicle in a molten state and maintaining its temperature within a predetermined limits through its travel to the outlet of the spray gun, an air compressor on the vehicle for delivering air under pressure to effect the transfer of the thermoplastic road-marking material from the storing means to and its discharge from the spray gun, means on the vehicle mounted behind and in alignment with the spray gun for spraying reflective material over the strip of thermoplastic material before the strip cools and sets, and means for controlling the operation of the spray gun.

A further spray gun may be arranged for spraying an adhesive material onto the road surface in advance of the first said spray gun and in the form of a strip which is wider than the strip of thermoplastic road-marking material.

The further spray gun may be provided with means for adjusting its position transversely of the path of travel of the chassis so as to enable the strip of adhesive material applied by it to be correctly aligned with the strip of thermoplastic road-marking material subsequently applied.

The thermoplastic road-marking material may be that forming the subject of copending patent application No. 655,345. In practice, the latter is adapted to be discharged from its spray gun at a high temperature, e.g., at a temperature in the region of 400 F., so that heat from thermoplastic material deposited on the adhesive coating will drive off solvents from the latter.

The interval between the time when a given point on the road surface is coated with the adhesive material and ice the time when the road-marking material is subsequently applied over the adhesive coating covering the same point is preferably not less than 1 second.

The width of the strip of adhesive material applied to the road surface is advantageously at least 2 inches wider than the superimposed strip of thermoplastic road marking material.

Preferably, loose foreign matter such as dust and surface water is removed from the road surface by a high pressure air jet located immediately in advance of the first spray gun. Alternatively, a rotary brush or sponge roller may be used for this purpose.

Thus there is provided a method of marking a road surface comprising the steps of spraying a moisture-repellant, solvent-based adhesive material onto the road surface to form thereon a strip-like coating of said adhesive material, spraying over said coating of adhesive material a molten thermoplastic road-marking material to form a strip-like road marking of smaller width than the said coating of adhesive material and spraying reflective media over the strip of thermoplastic roadmarking material before said strip of road-marking material cools and sets.

A control panel may be provided on the rear part of the chassis, which control panel incorporates switches for controlling the operation of the melting and storing apparatus as well as the operation of the further spray gun and the reflective material spraying means.

The panel may incorporate a rotary switch for selecting the pattern to be applied to the road surface from a number of alternative patterns, this rotary switch being connected in an electrical control circuit including a pulse counter to which pulses are transmitted from a pulse-transmitting tachometer driven by a wheel in contact with the ground and adapted to actuate a control switch in the operating circuit of the solenoid valve. Conventional circuit techniques are used to arrange that the valve is on and off for selected numbers of pulses from the tachometer.

The invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevation of a self-pro pelled road-marking apparatus,

FIG. 2 is a diagrammatic plan view of the apparatus shown in FIG. 1,

FIG. 3 is a block diagram of the circuits for compressed air, thermoplastic road-marking material, and reflection material in the apparatus shown in FIG. 1,

FIG. 4 is a block diagram of the heating system of the apparatus shown in FIG. 1,

FIG. 5 is a "block diagram of the electrical control circuitry of the apparatus of FIG. 1,

FIG. 6 is a diagrammatic side elevation of a further self-propelled road-marking apparatus in which parts corresponding to those shown in FIGS. 1 and 4 are given corresponding reference numerals, and

FIG. 7 is a diagrammatic plan view of the apparatus shown in FIG. 6.

Referring to FIGS. 1 and 2 of the drawings, the various component parts of the road-marking apparatus are all mounted either on a large size lorry chassis of conventional design or on a guide arm 11 connected to the front end of this chassis. The guide arm 11 is provided at its front end with a castor wheel 12 and is pivotably connected at its rear end to the chassis so that it can be swung up into the position indicated in broken lines at 11 in FIG. 1 when not in use. As can be seen in FIG. 2, the guide arm 11 is connected to the front end of the chassis at a point close to the near side thereof and extends forwardly from this point at a small angle in the direction towards the near side. A bracing arm 13 has its rear end mounted for pivotal movement about a horizontal axis aligned with the pivotal axis of the guide arm 11 and has its front end connected to a split collar clamped around the guide arm 11 approximately midway between the front and rear ends of the latter.

The chassis is provided with a drivers cab 14 within which are provided dual steering, braking, accelerator and like controls, i.e., two complete sets of such controls are provided respectively on the offside and nearside.

Mounted on the chassis close behind the drivers cab 14 is an air compressor unit 15 driven by a diesel engine and adapted to supply compressed air at 100 p.s.i. Three further units are mounted one behind the other on the part of the chassis to the rear of the air compressor unit 15, namely a melting and storage unit 16 for thermoplastic road-marking material, a pressurized container 17 for reflective material, and a control panel 18.

The melting and storage unit 16 includes a container 37 (FIG. 4), fitted with a heat-exchanger 38 by which thermoplastic road-marking material in the container 37 is heated up to 400 F. For this purpose, mineral oil is heated by a Beverley heater 39 and continuously circulated through melter racks which are arranged within the container 37 and constitute the heat-exchanger 38. Molten thermoplastic road-marking material is transferred alternately to two jacketed pressure-storage vessels (shown schematically as a unit 40 in FIG. 4) located beneath the container 37 at a rate of two tons per hour.

The pressurized container 17 shown in FIGS. 1 and 2 is designed for storage of reflected material such as Ballotini beads at a pressure of up to 30 p.s.i.

The control panel 18 is arranged so that it can be operated by a person seated either on a near-side seat 19 or on an off-side seat 21.

Mounted on the guide arm 11 a short distance behind the castor wheel 12 is a device 22 for delivering a jet of air downwardly onto the road surface beneath it. The supply of compressed air to this device 22 from the compressor unit 15 is controlled from the drivers cab 14 by control means operated by the driver.

Immediately behind the device 22 is a spray gun 23 for spraying an adhesive agent on the road surface. This spray gun 23 is adjustable transversely to enable the strip of adhesive deposited thereby to be aligned with the markings applied subsequently by

guns

24, 25 described more fully later. The spray gun 23 is adapted to be supplied with a tack-coating material from an airpressurized container 20. The supply of this material to the spray gun 23 is controlled by .a solenoid-actuated valve operable by a person seated at the control panel 18.

The

guns

24, 25 are mounted on a carriage 26 which is provided at its leading end with a castor wheel 27 and is connected by parallel links 28 to a supporting bracket 29. The bracket 29 is fixed to a transverse slide 31 by which it can be moved into appropriate positions for nearside, centre or off-side marking.

The gun 24 is adapted to be supplied with molten thermoplastic road-marking material from the melting and storage unit 16 via jacketed pipes. Heated mineral oil from the heat-exchanger of the unit 16 is circulated through the jacket spaces of these pipes so as to maintain a minimum temperature of 400 F. at the nozzle mouth of the gun 24.

The gun 25 is connected by pipes to the pressurized container 17.

The

guns

23, 24 and 25 have been described above as single guns, but when it is required to spray a road width of more than 6" in width, each such single gun would in practice be replaced by two or more guns located sideby-side.

Pipes

41, 42, 43, 44 and 45 shown in FIG. 3 supply compressed air from the compressor 15 to the gun 22, the container 20 for adhesive, the pressure vessels 40,

the container 17 for reflective material and to a control valve 46, and to the

guns

24 and 25, respectively.

The control valve 46 is of the conventional type in which the application of a predetermined air pressure to one side of an actuating member causes the actuating member to move and so open the valve to allow, in the present case, molten thermoplastic road-marking material to flow through the valve, removal of the predetermined air pressure causing the valve to close.

Each of the

guns

24 and 25 incorporates a control valve of the type described herein before, application of the predetermined air pressure to the control valve of the gun 24 enabling the molten thermoplastic road-marking material to flow through the gun 24, and application of the predetermined air pressure to the control valve of the gun 25 enabling the reflective material from the container 17 to flow through the gun 25.

Compressed air for driving the molten thermoplastic road-marking material from the pressure vessels 40 and the reflective material from the container 17 is obtained from the compressor 15 by way of the pipes 43 and 44 respectively.

The application of the predetermined air pressure to the control valve 46 is controlled by a solenoid-actuated valve 48.

Another solenoid-actuated valve 47 controls the release of air pressure in the pressure in the pressure vessels 40 to the atmosphere. In operation, the

valves

47 and 48 are actuated to allow molten thermoplastic roadmarking material to flow from the container 37 under gravity to the pressure vessels 40, the control valve of the gun 24 being closed. The

valves

47 and 48 are then closed and pressure builds up to a predetermined valve in the pressure vessels 40.

A third solenoid-actuated valve 49 controls the supply of compressed air to the control valves of the

gun

24 and 25. Energisation of the splendid solenoid 50 of the valve 49 will be described hereinafter in more detail with reference to FIG. 5.

It will be apparent that for each further pair of guns for spraying road-marking material and reflective material respectively, a further solenoid-actuated valve will be required.

Two further solenoid-actuated valves 51 and 52 control the flow of adhesive from the container 20 to the gun 23 under the pressure applied through the pipes 42, and the supply of compressed air to the gun 22, respectively.

The heating system for the thermoplastic road-marking material will now be described with reference to FIG. 4.

In the heater 39, mineral oil is heated to a temperature of 400 F., the heater being thermostatically controlled to maintain the mineral oil at this temperature.

The mineral oil passes out of the heater 39 by way of a pipe 53 and returns by way of a pipe 54 under the action of an electric pump 55. The rate of working of the pump 55, and hence the rate at which the mineral oil is circulated, is controlled by a thermostat 56, located in the container 37 in which the thermoplastic road-marking material is melted, which controls the power supply 56' of the pump 56,

The pipe 53 includes a temperature-sensitive three-way valve 57 which allows the mineral oil to flow through heater-jackets 58 surrounding the pressure vessel 40 only when the temperature of the plasticizer thermoplastic road-marking material is below 400 F., the valve 57 otherwise operating to direct the minerial oil through a by-passpipe 59 which conveys the mineral oil to a like temperature-sensitive three-way valve 60 at the outlet of the temperature jackets 58.

Two further temperature-sensitive three-way valves 61 and 62 determine whether the mineral oil flows through the jackets 63 and 64 of the pipe and the gun 24 or through a further by-pass pipe 65.

The mineral oil finally passes through the heat-exchanger 38 in the container 37 before entering the pump 55. The container 38 is preferably provided with a jacket (not shown) having an associated by-pass pipe (not shown) through which the mineral oil may pass.

From FIG. 1 it will be seen that a short distance in front of the rear wheels of the chassis, there is arranged a skip liner indicated generally at 32. This skip liner has a wheel 33 which is adapted, when the skip liner is in operation, to be rotated by contact with the road surface. A disc 34, which is belt-driven by the wheel 33, carries a ring of magnets which is arranged to cooperate with a reed switch 35 connected by leads 36 in an electronic circuit containing a pulse counter (FIG. 5). A rotary switch (shown in FIG. 5) mounted in the control panel 18 is used for selecting the pattern to be applied to the road, e.g. either a continuous line or an interrupted line consisting of line markings of predetermined lengths alternating with gaps of predetermined lengths. The pulses from the reed switch are counted in a manner determined by the setting of the rotary switch and the resulting sig nals are issued to operate a solenoid-actuated valve which controls the supply of compressed air to the valves in the

guns

24 and 25.

In FIG. 5 the rotary switch is shown as two rotary switches 70 which in practice are ganged together. The circuit shown in FIG. 5 includes a source 71 of electric power connected to one contact of the reed switch 35, the other contact of the reed switch 35 being connected to the fixed contact of a manually operable two-position switch 72 mounted in the control panel 18. When the disc 34 rotates at a steady rate, the reed switch opens and closes regularly and thus when the switch 72 is in the position shown a regular train of pulses is applied to the input connection of a first monostable multivibrator circuit 73 which serves as a pulseshaper. In one embodiment the interval between two pulses applied to the monostable circuit 73 corresponds to an advance of six inches by the vehicle. The output of the monostable circuit 73 is applied through respective capacitors 74 of equal capacitance to the input connections of two further

monostable multivibrator circuits

75 and 76. In a pattern-depositing operation, only one or the other of the

circuits

75 and 76 produces output pulses at any time. The output connections of the

monostable circuits

75 and 76 are respectively connected to the input connections of two pulse-frequency dividing circuits 77 and 78 including respective capacitors 79 and 80. Each of the circuits 77 and 78 is of the type in which the respective capacitor, 79 or 80 as the case may be, is charged in steps, corresponding to input pulses, up to a predetermined voltage at which a discharge circuit for the capacitor opens and the capacitor discharges rapidly, thereby producing a pulse at the output connection of the pulse-frequency dividing circuit. Thus, in operation when, for example, the monostable circuit 75 is producing output pulses, the capacitor 79 is charged in steps by these output pulses until the predetermined voltage is reached whereupon the capacitor 79 discharges rapidly and the pulse-frequency dividing circuit 77 applies a short pulse to one input of a bistable multivibrator circuit 81 which serves a control switch. When operating, the monostable circuit 76 and the pulse-frequency dividing circuit 78 co-operate in the same manner to supply a short pulse to the other input of the bistable circuit 81. Thus the

monostable circuits

75 and 76 with the pulse-frequency dividing circuits 77 and 78 act as a counter. The bistable circuit 81 changes from one of its states to the other whenever it receives an input pulse from the circuit 77 or from the circuit 78 since it is arranged that such inputs are ap plied alternately, as will be apparent from the following description.

On output connection of the bistable circuit 81 is connected to the input connection of an amplifier 82 of which the output connection is connected to one contact of a manually operable switch 83 mounted in the control panel 18. The other contact of the switch 83 is connected to one fixed contact of a manually operable three-position switch 84. The movable contact of the switch 84 is connected to the solenoid 50, so that when the movable contact of the switch 84 is in the position shown in FIG. 5 the solenoid 50 is energised when the bistable 81 is in one of its states and is de-energised when the bistable 81 is in the other of its states.

The energisation of the solenoid 50 can also be controlled manually since the other fixed contact 85 of the switch 84 is connected to the power supply 71. In controlling the energisation of the solenoid 50 manually, the movable contact of the switch 84 is placed in contact with the fixed contact 85 to energise the solenoid 50, and is placed in its central position, at which it is in contact with neither of the fixed contacts, to de-energise the solenoid 50.

An indicating light 86 is provided at the output connection of the amplifier 86 to indicate the presence of an output from the amplifier 86.

Where more than one gun for the thermoplastic roadmarking material and one gun for the reflective media is provided, further solenoids 87 with associated three-position switches 88 are provided. For example, there are shown in FIG. 5 two further solenoids 87, so that two further guns for the thermoplastic road-marking material and two further guns for the reflective media can be controlled by the circuit shown in FIG. 5. It will be apparent that, with a suitable amplifier 82 and source 71, as many further solenoids 87 as desired may be added to the circuit shown.

Since the solenoid 50, when the switch 84 is in the condition shown, is energised when the bistable circuit 81 is in one state and is de-energised when the bistable circuit 81 is in the other state, the

guns

24 and 25 are spraying when the bistable circuit 81 is in the said one state and are not spraying when the bistable circuit 81 is in the said other state.

The output connections 89 and 90 of the bistable circuit 81 are connected to the

monostable circuits

75 and 76 respectively in such a manner that when the bistable circuit 81 is in one of its states the monostable circuit 75 is rendered inoperative and the monostable circuit 76 is rendered operative, and that when the bistable circuit 81 is in the other of its states the monostable circuit 75 is rendered operative and the monostable circuit 76 is rendered inoperative. The relationship between the input connections and output connections 89 and 90 of the bistable circuit 81 is so arranged that, for example, when the monostable circuit 75 is operative and the pulse-frequency dividing circuit 77 consequently eventually applies a pulse to the bistable circuit 81, the application of that pulse causes the monostable circuit 75 to be rendered inoperative and the monostable circuit 76 to be rendered operative. It will be realised that in this way one of the

monostable circuits

75 and 76, say circuit 75, is operative when the

guns

24 and 25 are spraying, and the other, circuit 76, is operative when the

guns

24 and 25 are not spraying. The number of pulses from the reed switch 35 during which the monostable circuit 75 remains operative is dependent upon the number of output pulses from the circuit 75 required to cause the capacitor 79 to be charged up to the predetermined voltage. The predetermined voltage is fixed and thus the lengths of the output pulses from the circuit 75 determine the number of such pulses required. The time constant and hence the lengths of the output pulses produced by the circuit 75 is arranged to be variable by means of the rotary switch 70, as will now be explained.

The monostable circuit 75 is connected through a manually operable two-position switch 91 having its movable contact biased into the position shown to a source of variable voltage 92 incorporating the rotary switch 70. Each position of the rotary switch 70 corresponds to a different one of a plurality of difierent voltages and hence, by virtue of a manner of connection of the switch 91 to the monostable circuit 75 well known to those skilled in the art, to a different one of a plurality of different time constants of the monostable circuit 75.

The number of pulses from the reed switch 35 during which the monostable circuit 75 will remain operative can therefore be set at any one of a plurality of different valves by means of the rotary switch 70.

A switch 93 and a source 94 serve the same function in respect of the monostable circuit 76.

Thus the setting of the switches 70 determines both the number of pulses from the reed switch 35 during which the

guns

24 and 25 are spraying and the number during which they are not spraying. In other words, the setting of the switch 70 determines the length of the road marks deposited and the length of the gaps between successive road marks.

Two sources 95 of resetting voltages are connected to respective fixed contacts of the switches 91 and 93 for resetting the

monostable circuits

75 and 76. Two switches 96 and two switches 97 are also connected to the sources 95. Momentary closure of one of the switches 96 resets the bistable circuit 81 in one of its states, which state depending upon which of the switches 96 is momentarily closed. Momentary closure of one of the switches 97 causes the capacitor of the associated pulse-frequency dividing circuit to be charged to the predetermined voltage. In practice, the switch 91 is ganged to one of the switches 96 and to one of the switches 97, the switch 93 being ganged to the

other switches

96 and 97 and the arrangement being such that by momentarily turning the movable contact of the switch 91 to its reset position, the whole circuit is set into a condition corresponding to, say, the start of the deposition of a road mark, and that similar use of the switch 93 sets the whole circuit into a condition corresponding to the start of the gap between successive road marks. The details of such an arrangement will be apparent to those skilled in the art and therefore are not further described herein.

A manually operable switch 98 mounted on the control panel 18 and set open, as shown, when a road-marking operation is in progress is provided to enable the functioning of the control circuit to be checked visually by means of observation of the light 86. To carry out such checking, the switch 72 is turned to its other position, thus connecting the switch 98 to the monostable circuit 73 and disconnecting the reed switch 35 therefrom, and the switch 83 is opened to prevent accidental operation of the

spray guns

24 and 25. The switch 98 is then closed repeatedly to simulate operation of the reed switch 35. By counting the number of successive closures of the switch 98 during which the light 86 remains energised and then those during which the light 86 remains de-energised, it is possible to ascertain whether the control circuit is operating in accordance with the intended functioning determined by the setting of the rotary switches 70.

It will be apparent that the disposition of the magnets on the wheel 34 must be arranged to cause the reed switch 35 to open and close in as precise a manner as possible on rotation of the wheel 34.

The road wheel 33 which drives the disc 34 may also advantageously be used to drive a speedometer adapted to give accurate measurement of the speed of the vehicle over the range of low speeds, for example up to ten miles per hour, in which road-marking operations are effected. The driver of the vehicle can then more readily maintain a steady speed during such operations.

An electric circuit (not shown) for energising the solenoid of the solenoid-actuated valve 52 (FIG. 3) is controlled by a switch accessible to the driver of the vehicle.

Further electric circuits (not shown) for energising the solenoids of the solenoid-actuated

valves

47, 48 and 51 are controlled by manually operable switches mounted in the control panel 18.

In operation, the vehicle is driven forward at a speed of between 5 and 10 miles per hour, the driver taking care to ensure that he keeps a sighting pin (not shown) on the front end of the arm 11 aligned with the road markings to be renewed or with markings applied at intervals along the road to guide him. As the vehicle travels forward the various guns are operated as follows.

The driver operates the gun 22 whenever necessary to remove dust or other foreign matter or free surface water from the road surface. If the road surface is damp or covered with a frosty deposit, the operator seated at the control panel 18 actuates the appropriate control to cause a strip of adhesive agent to be deposited by the gun 23. The width of this strip will have been predetermined, by adjusting the height of the gun 23 above the road surface and, if necessary, by adding an additional gun or guns, so that the width of the strip of adhesive applied will be approximately two inches wider than the width of the road marking subsequently to be applied by the

guns

24, 25.

When the transverse slide is adjusted for off-side marking, the guide arm 11 must also be changed over to the off-side.

A suitable adhesive material may comprise a solution of a tough synthetic elastomer in a medium which comprises at least one hydrocarbon solvent in which the elastomer is readily soluble and at least one volatile, non-flammable solvent of specific gravity greater than unity, the solution being of a sufficiently low viscosity to enable it to be sprayed and the non-flammable solvent being present in sufiicient amount for the solution to have a specific gravity greater than unity and an open flash point above 75 F.

The adhesive material preferably also contains a cationic surface-active agent, to bring abuot preferential wetting of a wet surface by the composition, with displacement of the water. Examples of such compounds which have proved very useful are long chain cyclic amines.

In preparing one example of an adhesive for use in the present invention, sufficient of a block copolyrner of styrene and butadiene (Cariflex Kl01-Shell Chemicals Ltd.) is added to an equal volume of turpentine and trichloroethylene to produce a 10% solution by weight. For this purpose, every 2 gallons of solvent mixture requires 2 /2 lb. of the rubber. The mixture is stirred continuously with an efficient paddle stirrer for several hours, until complete solution is obtained. To every 2 gallons of this solution is added 1 oz. of a long chain cyclic amine surfactant (Bitran H-Glover Chemicals Ltd.) which is well stirred in, and the composition is then transferred to S-gallon drums.

FIGS. 6 and 7 show another embodiment of apparatus according to the present invention, which differs from the first described hereinbefore in that no container for melting the thermoplastic road-marking material is provided on the chassis of the vehicle, the pressure vessel 40 having two inlet-filling openings, each shown sealed by a lid 101, through which molten thermoplastic road-marking material can be delivered from an ancillary vehicle (not shown) bearing apparatus for melting the roadmarking material. The vessel 40 incorporates a device (not shown) for stirring the molten thermoplastic roadmarking material therein, the device being driven by compressed air supplied by the compressor 15.

A container 102 for fuel, such as liquid petroleum gas, for the heater 39, is mounted on the vehicle.

The operation of the

guns

24 and 25 is controlled in the same manner as described hereinbefore in relation to the embodiment shown in FIGS. 1 to 5.

A device for delivering a jet of air downwardly onto the road surface beneath may be provided on the chassis of the vehicle shown in FIGS. 6 and 7 at a position closer to the drivers cab 14 than the gun 24, the guide arm 11 of the previously described embodiment being dispensed with in the case of this smaller vehicle.

lfurthermore, another ancillary vehicle carrying a pressurised supply of adhesive and equipped with a spray gun corresponding to the gun 23 of the previously described embodiment may be employed to lay a trail of adhesive before the vehicle shown in FIGS. 6 and 7.

It is preferable, for the purpose of obtained good reflection, in embodiments of the invention that, where the reflective material is in the form of beads of transparent material such as Ballotini heads, the media should be sprayed at a velocity sufficient to cause those beads which strike the surface of the thermoplastic material to become half embedded in that material. Also, the beads should be sprayed in excess of the quantity required to cover the surface of the road marks since the excess beads which remain loose act as a sand and thus help to prevent the tread of the tyres of vehicles passing over the marks soon after the deposition" from picking up the thermoplastic road-marking material. It has been found, moreover, that the embedding of cool Ballotini beads in the surface of a thermoplastic road mark enables a protective skin of set thermoplastic material to form rapidly over the mark.

Compressed air for use in atomising the adhesive and thermoplastic materials in the guns is, if required, obtained from the air compressor 15, through supply lines (not shown) which include respective manually operable valves accessible to a person seated at the control panel 18 at the rear of the vehicle.

The spray gun 25 can be a conventional gun for spraying Ballotini beads or the like.

We claim:

1. A road-marking apparatus, comprising:

a self-propelled, steerable wheeled chassis,

a guide arm projecting forwardly from said chassis,

a first downwardly directed spray gun mounted on said guide arm and arranged for spraying an adhesive material onto a road surface beneath said chassis to form a coating thereon in the form of a strip,

a second spray gun mounted on said chassis in a position near the rear end of the latter and in longitudinal alignment with said first spray gun and arranged for spraying a molten thermoplastic road-marking material in the form of a narrower strip over the strip coating applied by said first spray gun,

a container mounted on said chassis for storing said adhesive material under pressure,

means mounted on said chassis for melting said thermoplastic road-marking material and storing it under ressure,

pipes connecting said container to said first spray gun and said melting and storing means to said second spray gun,

means for maintaining the temperature of said thermoplastic road-marking material within predetermined limits throughout its travel from said melting and storing means to the outlet of said second spray gun,

an air compressor mounted on said chassis for delivering air under pressure to effect the transfer of said adhesive material from said container to and its discharge from said first spray gun, as well as the trans fer of said thermoplastic road-marking material from said melting and storing means to and its discharge from said second spray gun,

control means for controlling the operation of said first and second spray guns and means behind and in alignment with said second spray gun for spraying reflective material over the strip of thermo-plastic road-marking material applied by said second spray gun before said strip of road-marking material cools and sets.

2. Apparatus according to claim 1, wherein said control means includes:

a solenoid-actuated valve controlling the supply of compressed air from said air compressor to said first and second. spray guns, and

manually operable switches on said chassis connected in the electric control circuit of said solenoid-actuated valve.

3. Apparatus according to claim 2, wherein means are provided on said guide arm in advance of said first spray gun for discharging a jet of high-pressure air onto the road surface.

4. Apparatus according to claim 3, wherein there are also provided:

a road wheel connected to said chassis and adapted to be rotated by contact with the road surface as the chassis advances,

a pulse-transmitting tachometer drivably connected to said road wheel and adapted to transmit pulses when driven by said road wheel,

an electrical control circuit,

a rotatary pattern-selecting switch connected in said control circuit for selecting, from among a number of different road-marking patterns, a road-marking pattern to be applied to the road surface,

a pulse counter connected in said control circuit and adapted to count the pulses transmitted by said tachometer and to transmit signals related to such pulse counting in a manner determined :by the setting of said rotary switch, and

a control switch connected in the operating circuit of said solenoid valve and arranged to control the opening and closing of said solenoid valve in accordance with the signals transmitted by said pulse counter.

. A road-marking apparatus, comprising:

a self-propelled, steerable wheeled chassis, a spray gun mounted on said chassis and arranged for spraying a molten thermoplastic road-marking material on to a road surface beneath said chassis to form a coating thereon in the form of a strip,

means mounted on said chassis for storing said molten thermoplastic road-marking material under pressure, pipes connecting said storing means to said spray me a iis for maintaining the temperature of said thermoplastic road-marking material within predetermined limits throughout its travel from said storing means to the outlet of said spray gun,

an air compressor mounted on said chassis for delivering air under pressure to effect the transfer of said thermoplastic road-marking material from said storing means to and its discharge from said spray gun,

means mounted on said chassis behind and in alignment with said spray gun for spraying reflective material over the strip of thermoplastic road-marking material applied by said spray gun before said strip cools andlsets,

control means for controlling the operation of said spray gun, said control means including:

a solenoid-actuated valve controlling the supply of compressed air from said air compressor to said p y a road wheel connected to said chassis and adapted to be rotated by contact with the road surface as the chassis advances,

a pulse-transmitting tachometrical device drivably connected to said road wheel and adapted to transmit pulses when driven by said road Wheel,

an electrical control circuit connected to receive said pulses,

a pattern-selecting switch connected in said control circuit for selecting, from among a number of different road-marking patterns, a road-marking pattern to be applied to the road surface,

pulse-counting circuit means connected in said control circuit and adapted to count the pulses transmitted by said tachometrical device and to transmit signals related to such pulse counting in a manner determined by the setting of said rotary pattern-selecting switch to the operating circuit of said solenoid-actuated valve to control the opening and closing of said solenoidactuated valve in accordance with the said signals transmitted by said pulse counter.

6. Apparatus as claimed in claim 5, wherein means are provided in advance of said spray gun for discharging a jet of high-pressure air on to the road surface.

7. Apparatus as claimed in claim 5, wherein a further downwardly directed spray gun is arranged for spraying an adhesive material on to the road surface in advance of the first said spray gun and in the form of a strip which is wider than the strip of thermoplastic road-marking material to be formed thereon,

a container is mounted on said chassis for storing said adhesive material under pressure, and

a pipe is provided connecting said container to said further spray gun,

said air compressor being adapted to effect the transfer of said adhesive material from said container and its discharge from said further spray gun.

8. Apparatus as claimed in claim 5, wherein a manually-operated switch is included in the operating circuit of the said electrically operable valve and is arranged for overriding the said pulse counting circuit means and for controlling the said valve.

9. Apparatus as claimed in claim 5, wherein the said pulse-transmitting tachometrical device is adapted to generate one pulse for each advance of six inches by the vehicle.

References Cited UNITED STATES PATENTS 2,026,870 1/ 1936 Dalton 94-44 2,076,370 4/1937 Hollinshead 94-44 2,357,930 9/1944 Clark 94-44 2,691,923 10/1954 Huck 94-44 3,018,704 1/1962 Searight 94-44 3,046,854 7/1962 Wilson 94-44 3,262,375 7/ 1966 Eigenmann 941.5 3,326,098 6/1967 Boettler 941.5 XR 3,356,261 12/1967 Stein 94-44 XR 2,430,534 11/ 1947 Rodli.

JACOB L. NACKENOFF, Primary Examiner U.S. Cl. X.R.