GB2344369A

GB2344369A - Radiant heating device for use in repairing asphalt surfaces

Info

Publication number: GB2344369A
Application number: GB9824226A
Authority: GB
Inventors: Paul Hutchinson
Original assignee: NUPRO Ltd
Current assignee: NUPRO Ltd
Priority date: 1998-11-06
Filing date: 1998-11-06
Publication date: 2000-06-07
Anticipated expiration: 2018-11-06
Also published as: GB9824226D0; GB2344369B

Abstract

A radiant heating device suitable for use in repairing asphalt surfaces comprises a closed frame (1) containing a downwardly-directed radiant heating surface (19) and at least four supporting legs (2) for the frame, the legs being slidably mounted whereby the extension of each leg below the frame may be varied individually. The legs are suitably mounted on horizontally-rotatable arms (3), so that the legs may be positioned at the side or at an end of the frame. The flammable gas and air are introduced into the frame to be burnt on the radiant heating surface via a blower. The gas supply also includes a control for automatically switching the gas flow on and off according to a predetermined cycle of off and on time periods, the cycle being manually chosen from a selection of predetermined cycles. The air and gas are delivered separately to nozzles in an inlet in the frame, the inlet having a flame arrester adjacent the nozzles to mix the gas and air before passing into the frame. A sensor is used to detect when the correct temperature has been reached and to switch off the gas supply. The radiant heating material is a refractory mineral wool.

Description

RADIANT HEATING DEVICE FOR USE IN REPAIRING ASPHALT SURFACES Field of the Invention This invention relates to a radiant heating device suitable for use in repairing asphalt surfaces, for example cracked or damaged road or pavement surfaces.

Background to the Invention Asphalt road surfaces deteriorate through a number of different mechanisms, such as wear caused by traffic over the surface, gradual loss of plasticising components giving rise to brittleness and cracking, frost damage after cracking has occurred, and repairs following trenching for pipe or cable laying. In the latter case, although the repairs are satisfactory in the short-term, settlement of the underlying material, and failure of the bitumen seal along the joint with the existing surface, necessitate resurfacing or fresh repairs after a relatively short time.

The repair of asphalt surfaces is costly. Conventionally, this involves the removal of at least a surface layer and then laying new asphalt material to replace the removed material. Costs arise in the disposa of the old material and in the provision of the new, and in the prolonge closure of the road, or at least part of it, while the repair operation is carried out. To overcome some of these difficulties, new processes have been developed in which the road surface is heated to soften the asphalt material to a suitable depth, followed by breaking up of the softened surface, addition of asphalt rejuvenating materials and, if required, additional asphalt to make up for lost material from potholes or cracks, mixing in situ, and then rolling to provide a finished surface.

Apart from the benefits in terms of speed, cost and the saving of materials, the repair is more durable then conventional repairs, because there is no need to provide a bitumen seal around the perimeter of the repair in an effort to deal with the discontinuity between the old and the new material. This interface between the two different materials is avoided in the new process because the softening of the material in situ effectively welds the repair into the surrounding road surface.

In carrying out the new processes, precise control of the heating of tub rad surface is required. It is necessary to soften the surface to a depth of, for example, 3 to 4 inches (75-100mm), and this requires heating for a sufficient time to allow penetra tion from the surface to the desired depth, while not causing excessive heating at the surface, since the asphalt materials can become burnt, rendering them unsatisfactory for surfacing purposes and therefore requiring their removal, thus defeating the object of the new process.

Typical heating devices used for softening asphalt surfaces comprise rectangular frames closed on five faces and with the remaining face formed from a gas-permeable refractory material such as a mineral wool blanket or a metal gauze. A mixture of flammable gas (for example propane) and air is fed into the frame and ignited on the external surface of the refractory material, heating the material and causing it to radiate heat. The frame is positioned over the surface to be treated for a sufficient time to achieve suitable softening. Problems which arise with such devices include control of heating so that softening is achieved to the right depth without burning, safety, since relatively large volumes of flammable gas are involved, economy of gas consumption and convenience of use for different sizes of repairs required.

Summary of the Invention According to the invention, there is provided a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and at least four supporting legs for the frame, the legs being slidably mounted whereby the extension of each leg below the frame may be varied individually. The device can thus be used on uneven ground.

Another aspect of the invention provides a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and at least four supporting legs for the frame, each leg being mounted on a supporting arm pivotally connected to the frame so as to be rotatable in a horizontal plane so that the associated leg may be alternatively positioned at the side or at an end of the frame. This arrangement permits the device to be used close up to a kerb, with the legs moved to the ends of the frame so that the side of the frame can rest against the kerb. With a combination of the two features, the device can be used with two of the legs on the kerb, again facilitating close approach, or it can be used to treat a raised pavement surface, with two of the legs resting on the pavement and the other two out to one side and resting on the adjacent, and lower, road surface.

The legs are suitably provided with wheels on the ends, suitably castor-mounted, to permit the device to be manoeuvred readily.

Yet another aspect of the invention provides a combination of a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and at least four supporting legs for the frame, each leg having a wheel thereon, and a transporting vehicle therefor, the vehicle having a tilting support with attachment means for securing an edge of the frame thereto, whereby the frame may be lifted up to rotate about one set of wheels at one end and the other end is attached to the tilted support, which is then returned to a generally horizontal position to lift the other end of the frame off the ground to permit it to be transported. The vehicle is suitably a trailer vehicle, conveniently having just two wheels to permit the support thereon readily to be tilted, and facilitate manoeuvring of the vehicle.

The invention also provides a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardlydirected radiant heating surface and supply means for introducing flammable gas and air into the frame to be burnt on the radiant heating surface, the supply means comprising a blower to introduce air and a gas supply, the gas supply including control means for automatically switching the flow of gas on and off according to a predetermined cycle of off an on time periods, and adjustment means for manually selecting one of a plurality of predetermined cycles in order to change the heating effect of the heating surface on the asphalt surface.

A still further aspect of the invention provides a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and supply means for introducing flammable gas and air into the frame to be burnt on the radiant heating surface, the supply means comprising a blower to introduce air and a gas supply, the air and the gas being delivered separately to nozzles in an inlet means in the frame, the inlet means compris ing a flame arrester adjacent to the nozzles such that the gas and air tend to mix in passage through the arrester before passing into the frame. In this way, mixing of flammable gas and air occurs as close as possible to the permeable material constituting the radiant heating surface, avoiding the risk of flashback of the flame and assisting in control of the on-off heating cycle by ensuring that the volume of gas remaining to be burnt when the gas supply is shut off is at a minimum.

The device may comprise at least one heat sensor adapted to detect the temperature of the asphalt surface being heated. The sensor may be operatively linked to the gas supply control to shut off the gas supply when the correct temperature has been reached, further reducing the risk of overheating, and thereby damaging, the asphalt.

Flame failure sensors may also be included to shut-off gas flow if the flame is extinguished. Spark igniters will typically be included to ignite the gas automatically on the surface of the gas-permeable radiant heating material, which is suitably a refractory mineral wool.

The invention further provides a radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a plurality of frames of differing sizes, a flammable gas supply device connectable selectively to any or each of the frames, means for providing a supply of air to any or each of the frames, a transporting vehicle for detachably mounting the largest of the frames, and means for mounting the other frames on the upper surface of the largest of the frames when it is mounted on the vehicle, or for stacking the other frames thereon for transport.

The arrangement provides great flexibility in the use of the device, with the pos sibility of utilising the correct size of frame for any particular job, small frames being usable for small jobs without the use of an excessive amount of gas, and with the possibility of combining different frames to treat a long length of road at the same time. Since the frames are separable, it is possible for several different, but adjacent, repairs to be carried out at the same time, again affording a saving in time and cost.

Brief Description of the Drawings In the drawings, which illustrate a device according to an exemplary embodiment of the invention: Figure 1 is a perspective view of the device in use on a stepped surface such as a pavement or sidewalk; Figure 2 is a side elevation of the device mounted on a trailer for transport; Figure 3 is a diagram illustrating the combustion control for the device; Figure 4 is an underneath plan view of the device with the radiant heating material removed, showing the fuel and air supply to two of the four cells therein; and Figure 5 is a side sectional view of the device shown in Figure 4.

Detailed Description of the Illustrated Embodiment The device comprises a heater frame 1 with four supporting legs 2, one at each corner thereof. Each leg 2 is carried by a swivel support 3 which permits the leg to rotate in a horizontal plane through approximately 90 so as to extend normally to the side 4 or the end 5 of the frame 1. The swivel support 3 can be locked in either position, and carries at its end a tube 6 in which the leg 2 is a sliding fit, a screw clamp 7 being provided to hold the leg at the desired vertical position relative to the support3.

By selecting either a side position or an end position for the legs 2, the end or side may be brought close to a vertical obstacle such as a kerb. Each leg 2 carries a castormounted wheel 8.

The vertical adjustment of each leg 2 permits adjustment of the height of the device above the surface to be treated, and also permits the device to be used on a narrow raised pavement 9, as illustrated. With one pair of legs 2 extended so that the wheels 8 are on the lower road surface and the other pair of legs raised to accommodate the height of the kerb 10, while keeping the frame 1 level, the device may be used to treat the surface of the pavement 9 where this is narrower than the frame 1. The ability to vary the height of each leg independently also allows the device to be used on uneven surfaces, while maintaining the frame 1 parallel to the surface.

Figure 2 illustrates the configuration of the device for transporting. The largest 1 of several frames of different sizes constituting a set of the devices is mounted on a trailer 11 consisting of a simple T-frame 12 with a draw-bar attachment 13 at one end.

One end of the frame 1 is hooked on to a mounting member 14 on the central spar of the T-frame with the T-frame rotated about the wheels 15, and then by returning the T frame of the trailer to the horizontal the frame 1 is lifted off the ground. Separate smaller heater modules 16 and 17 are removably mounted on the largest module or frame 1 for transport. Removal of the device from the trailer on arrival at a work site is essentially the reverse of the mounting operation, with the trailer being tilted about its wheels until the rearmost wheels on the frame 1 touch the ground. The front end of the frame 1 is then disengaged from the mounting member and lifted, permitting it to be rolled rearwardly of the trailer on the rear wheels 8. When clear of the trailer, the front end can then be lowered to the ground, and the additional modules can then be lifted off the frame 1 for use.

Figure 3 illustrates the burner control system. The largest frame 1 is divided into four separate heating panels 1a-1d, each with its own gas supply. Each heating panel comprises an enclosed compartment 18 with five steel walls and a lowermost face consisting of a mineral wool blanket19, as may be seen more clearly from Figure 5. Gas and air are introduced into each compartment 18 separately, as will be described in more detail hereinafter with reference to Figure 4. The flammable gas, for example propane, is supplied from a conventional cylinder 20 through a pressure control valve 21 to a solenoid valve 22 which in turn controls flow to a manifold 23, from which four separate valves 24 control the individual supply to each of the four panels through flexi- ble supply pipes 25. The solenoid control valve 22 is opened and closed in response to control signals from a timer control 26 which switches the flow of gas on and off according to a pre-set cycle which can be varied to increase or decrease the operating temperature of the panels by a manual control 27. The manual control 27 varies the relative lengths of the on and off periods within a predetermined range, so that the length of time of the off period is always sufficiently short to ensure that when the gas flow is restored ignition occurs at the external face of the mineral wool blanket. An electrically-powered fan 28 blows air through a supply pipe 29 to a central manifold 30 on the frame 1, from where it is distributed to each of the panels. The gas supply (2024,26,27) and the fan 28 can be combined into one module separate from any of the frames, and may be used with any of the frames or a combination of them.

Referring now to Figures 4 and 5, which show the fuel and air supply to only two out of the four panels for the sake of clarity, the air supply manifold 30 divides into a separate supply pipe 31 for each panei, while a separate gas connection 32 is provided in the ends of the frame for each. The gas and air are supplie to an inlet chamber 33 where they are mixed as they pass through a metal gauze flame arrester 34 to fill the compartment 18 above the blanket 19. The pressure in this space is sufficient to ensure that the gas mixture flows through the blanket 19, to be ignited on its lowermost surface, heating the surface sufficiently to radiate heat downwardly on to the asphalt surface below. In the event of a rupture of the blanket giving rise to ignition of the gas within the space above it, safety is ensured by the flame arrester, confining any resultant jet of flame to the interior of the panel, and obviating the risk of explosion. Safety devices may be incorporated in the panel to detect a sudden rise in temperature therein, indicating rupture of the blanket, and to send a control signal back to the gas supply to cut off the flow of gas.

Temperature sensors may be incorporated within the device to detect the temperature of the asphalt surface and to signal the gas supply to stop the flow of gas if the temperature approaches the level at which charring can occur.

Claims

1. A radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and at least four supporting legs for the frame, the legs being slidably mounted whereby the extension of each leg below the frame may be varied individually.

2. A radiant heating device according to Claim 1, wherein each leg is mounted on a supporting arm pivotally connected to the frame so as to be rotatable in a horizontal plane so that the associated leg may be alternatively positioned at the side or at an end of the frame.

3. A radiant heating device according to Claim 1 or 2, comprising supply means for introducing flammable gas and air into the frame to be burnt on the radiant heating surface, the supply means comprising a blower to introduce air and a gas supply.

4. A radiant heating device according to Claim 3, wherein the gas supply includes control means for automatically switching the flow of gas on and off according to a predetermined cycle of off an on time periods, and adjustment means for manually selecting one of a plurality of predetermined cycles in order to change the heating effect of the heating surface on the asphalt surface.

5. A radiant heating device according to Claim 3 or 4, wherein the air and the gas are arranged to be delivered separately to nozzles in an inlet means in the frame, the inlet means comprising a flame arrester adjacent to the nozzles such that the gas and air tend to mix in passage through the arrester before passing into the frame.

6. A radiant heating device according to Claim 4 or 5, comprising at least one heat sensor adapted to detect the temperature of the asphalt surface being heated.

7. A radiant heating device according to Claim 6, wherein the sensor is operatively linked to the gas supply control to shut off the gas supply when the correct temperature has been reached, further reducing the risk of overheating, and thereby damaging, the asphalt.

8. A radiant heating device according to any of Claims 3 to 7, comprising at least one flame failure sensor to shut-off gas flow if the flame is extinguished.

9. A radiant heating device according to any of Claims 3 to 8, comprising at least one spark igniter to ignite the gas automatically on the surface of the gaspermeable radiant heating material.

10. A radiant heating device according to any preceding claim, wherein the radiant heating material is a refractory mineral wool.

11. A radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a plurality of frames of differing sizes, a flammable gas supply device connectable selectively to any or each of the frames, means for providing a supply of air to any or each of the frames, a transporting vehicle for detachably mounting the largest of the frames, and means for mounting the other frames on the upper surface of the largest of the frames when it is mounted on the vehicle, or for stacking the other frames thereon for transport.

12. A radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and at least four supporting legs for the frame, each leg being mounted on a supporting arm pivotally connected to the frame so as to be rotatable in a horizontal plane so that the associated leg may be alternatively positioned at the side or at an end of the frame.

13. A radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and supply means for introducing flammable gas and air into the frame to be burnt on the radiant heating surface, the supply means comprising a blower to introduce air and a gas supply, the gas supply including control means for automatically switching the flow of gas on and off according to a predetermined cycle of off an on time periods, and adjustment means for manually selecting one of a plurality of predetermined cycles in order to change the heating effect of the heating surface on the asphalt surface.

14. A radiant heating device suitable for use in repairing asphalt surfaces, the device comprising a closed frame containing a downwardly-directed radiant heating surface and supply means for introducing flammable gas and air into the frame to be burnt on the radiant heating surface, the supply means comprising a blower to introduce air and a gas supply, the air and the gas being delivered separately to nozzles in an inlet means in the frame, the inlet means comprising a flame arrester adjacent to the nozzles such that the gas and air tend to mix in passage through the arrester before passing into the frame.

15. A radiant heating device according to any of Claims 1 to 10, wherein the legs are provided with wheels on the ends.

16. A radiant heating device, substantially as described with reference to, or as shown in, the drawings.

17. A combination of a radiant heating device according to Claim 15 and a transporting vehicle therefor, the vehicle having a tilting support with attachment means for securing an edge of the frame thereto, whereby the frame may be lifted up to rotate about one set of wheels at one end and the other end is attached to the tilted support, which is then returned to a generally horizontal position to lift the other end of the frame off the ground to permit it to be transported.

18. A combination according to Claim 17, wherein the vehicle is a trailer vehicle.

19. A combination according to Claim 18, wherein the trailer vehicle has two wheels to permit the support thereon readily to be tilted, and to facilitate manoeuvring of the vehicle.