EP0017499A1

EP0017499A1 - Heating apparatus

Info

Publication number: EP0017499A1
Application number: EP80301094A
Authority: EP
Inventors: Richard Leslie Cottingham; Ralph Alex Boyne; Anthony Clifford Hillman
Original assignee: THORMACK ENGINEERING Ltd
Current assignee: THORMACK ENGINEERING Ltd
Priority date: 1979-04-04
Filing date: 1980-04-03
Publication date: 1980-10-15
Also published as: GB2045840A

Abstract

Apparatus for heating material such as asphalt for filling potholes in which a drum (12) is rotatable about its axis (13) and has an outlet opening (15) at one end and a port (17) at the other end. An auger (36,37) is mounted within the drum (12) so that when the drum (12) is rotated in one direction material is discharged through the outlet opening end (15) and when it is rotated in the other direction it is moved away from the outlet opening (15). A flashback condition burner (18) is mounted with its discharge opening (18A) in the port (17) to discharge fully combusted hot gas into the drum to heat material therein. The burner can be dismounted to preheat and clean out a pothole in a road surface.

Description

The present invention relates to heating apparatus which is, for example, suitable for heating up road repairing materials.
When potholes appear in roadways, it is often advantageous to mend these as soon as is practicable after they are formed. However, this is often very difficult to achieve. The standard technique is for the repairer to obtain a lorry load of hot asphalt from an asphalt supplier. Asphalt consists largely of stones or grit and a binder, usually - bitumen, which is between 14 and 17% of the total. The asphalt is taken to the site where the repairs are to be effected. The repairs are carried out on the first few potholes, but after a while the asphalt becomes too cool to be readily usable and it is therefore usually wasted.
This is a very wasteful method of operating and is therefore not satisfactory.
British Patent Specification Nos. 435,951 and 521,990 describe machines in which aggregate is dried and heated in a drum rotatable about a horizontal axis by means of an oil fired burner, the discharge flame from which is projected into the drum. When the aggregate is hot, the burner is turned down, a door is shut and the bitumen is added. This is a laborious arrangement, does not provide intimate mixing and cannot be used to reconstitute unused asphalt. Specification No. 1,353,512 discloses a large scale plant of the type used by an asphalt supplier, which cannot be scaled down for small batch use and could not be used to reconstitute unused asphalt because the bitumen in such asphalt would catch alight.
It is now proposed, according to the present invention, to provide a heating apparatus comprising a drum rotatable about its axis, an outlet opening at one axial end of said drum, an auger arrangement within said drum to feed material within said drum axially thereof, a port at the other end of the drum, a flashback condition burner having a combustion chamber in which combustion takes place substantially completely within said combustion chamber, said burner being mounted with its discharge opening in said port and drive means to rotate said drum about its axis selectively firstly in one direction of rotation and secondly in the other direction of rotation.
With such an arrangement, the asphalt to be heated can be heated on site and indeed can be mixed at the same time. The material to be heated is fed in to the drum which is rotated in one direction to cause the material to be heated and mixed to flow away from the outlet opening towards the port. When the flashback condition burner is ignited, it produces a high velocity jet of very hot gases which will warm the asphalt sufficiently to make it workable. Since combustion is complete in the burner there is no tendency for the bitumen to ignite. Indeed the carbon dioxide and nitrogen in the products of combustion which enter the drum, and the very high velocity of the gases, would extinguish any flame in the drum.
When it has attained the desired temperature, the drum is caused to rotate in the opposite direction at which time the burner can be turned off. With the drum rotating in the opposite direction the auger causes the material to feed out of the outlet opening where it can be taken up by the workman in a suitable receptacle and used.
Advantageously, the flashback condition burner is releasably mounted with respect to the drum so that it can be readily dismounted. With this arrangement, it is possible to use the flashback condition burner to prepare the pothole prior to the application of the hot asphalt. Use of the burner will firstly blow out any dust or debris within the pothole and secondly, will heat the pothole so that it will form a good bond with the hot asphalt.
Preferably, the drum is mounted for rotation about a substantially horizontal axis and the drum is provided with a tapered portion which terminates in the outlet opening.
The apparatus can be used for mixing asphalt, rather than simply heating it. Stones or grit can be introduced into the drum first and dried. Desirably, the flashback condition burner is mounted in the port in the drum with clearance, so that air is entrained into the drum by the discharge gas stream. This has the advantage that the stones or grit will be dried more quickly. Bitumen can be added when it can be seen that there is little or no water vapour leaving the outlet opening, this indicating that the stones or grit are dry.
Although the drum is preferably filled through its outlet opening, a closable inlet opening, for example a door, could be provided in the drum at a location axially spaced from the outlet opening.
In order that the invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:-

Figure 1 is a side elevation of one embodiment of heating apparatus according to the invention; and
Figure 2 is an end elevation of the apparatus of Figure 1.

Referring now to the drawings, there is illustrated therein a heating apparatus which is mounted on a chassis 10 provided with roadwheels 11. A cylindrical drum 12 is mounted on the chassis for rotation about a substantially horizontal axis 13.
The righthand end of the drum, as seen in Figure 1, is tapered at 14 and terminates in a discharge opening 15.
At the other end of the drum, the end wall 16 is provided .with a central axial port 17 adjacent which is mounted a flashback condition burner 18, that is a burner which is powered by gas and compressed air and in which the combustion takes place completely within the combustion chamber. The burner is provided with an outlet opening 18A on the'right as viewed in Figure 1.
The burner is fed via line 19 with compressed air from a compressor (not shown) and with gas, for example, propane, from a cylinder (not shown) via line 20 and controlled by . valves 21 and 22 respectively, the mixture passing along line,18B.
The burner 18 is mounted in a cradle 23, in which it is releasably held in place. The cradle 23 is pivotally mounted on a hinged arm 24. The outlet opening 18A of the burner 18 is rather smaller than the port 17 so that air will be entrained into the drum by the discharge gases of the burner.
The drum is mounted for rotation on two running rings 30 and 31 and is supported by rollers 32 and 33 carried in frames 34 and 35 mounted on-the chassis.
It will be seen that there is mounted on the inside surface of the drum an auger arrangement including two helical augers 36 and 37, wound in the manner of a double start thread. A baffle 38 is arranged to bridge the two augers and is arranged on the axis 13 to overlie the discharge opening 15, the baffle being axially spaced from the discharge opening slightly inwardly of the outlet and of the cylindrical part of the drum.
In order to cause the drum to rotate, a motor 39 is mounted on the chassis and drive is achieved by a chain 40 passing round a toothed gearwheel on a gearbox 43 connected to a ring on the motor and around gear 41, on the drum, a chain guard 42 being provided for safety.
A chute 50 is pivotally mounted on the drum at 51 and is pivotable from the upper position illustrated in full to a lower position illustrated in phantom at 52.
In use, material to be mixed to form asphalt, that is bitumen and stones or grit, is introduced in through the outlet opening 15, using the chute in its upper position, and the drum is then caused to rotate in a direction such that the augers 36 and 37 tend to move the material to be mixed to the left in Figure 1, that is towards the end wall 16 and away : from the outlet opening 15. The compressor is put into operation to feed compressed air via valve 21 and gas is fed via valve 22 to provide a combustion-mixture which passes along line 38B to the chamber of burner 18, the mixture then being ignited. A hot blast of combustion gases is thus discharged into the drum. This operation is continued for a short time to ensure that the material within the drum is all heated to the desired temperature. The drum is then stopped and the burner 18 removed. The pothole to be treated is then cleaned out and preheated by means of the burner. The chute is moved to the lower position 52 and the drum is rotated in the opposite rotational sense so that hot asphalt can flow out of the outlet opening 15 under the action of the augers 36 and 37, and thence down the chute. The material is then placed in the pothole which will be hot and a good bond will be achieved between the asphalt and the surrounding road surfacing material.
The baffle 38 and to a certain extent the chute 50 in its upper position, serve to ensure that material is not blown out of the drum by the hot jet of combustion gases. They also reduce the noise of the burner 18. Since the combustion gases are fully burned in the burner there is no tendency for the material, such as bitumen, in the drum to ignite. This is particularly important when one is using the apparatus to reconstitute previously unused asphalt.
The arrangement of the present invention can be used in substantially all weathers. Even if the ground is wet and it is raining or snowing, or even if there is frost, the action of the burner on the road surface will ensure that the roadway is dry and clean and the fact that hot asphalt is immediately applied ensures a good bond so that further work need not be done at a later date. Furthermore, there need be little or f no waste of the asphalt material because this can be kept hot by replacing the burner from time to time. Furthermore, wet stones or grit can be dried prior to introducing the bitumen.

Claims

1. Heating apparatus comprising a drum rotatable about its axis, an outlet opening at one axial end of the drum, an auger arrangement mounted within said drum to feed material within said drum axially thereof, a port at the other end of the drum, a flashback condition burner having a combustion chamber and in which combustion takes place completely within said combustion chamber, said burner being mounted with its discharge opening in said port and drive means to rotate said drum about its axis selectively firstly in one direction of rotation and secondly in the other direction of rotation.

2. Apparatus according to claim 1, wherein said drum is mounted for rotation about a substantially horizontal axis.

3. Apparatus according.to claim 1 or 2, wherein the drum is provided with a tapered portion which terminates in said outlet port.

4. Apparatus according to claim 1, 2 or 3, wherein the flashback condition burner is releasably mounted with respect to the drum so that it can readily be dismounted.

5. Apparatus according to any preceding claim, wherein the flashback condition burner is mounted in the port with clearance so that air is entrained into the drum by the discharge gas stream of the burner.

6. Apparatus according to any preceding claim, wherein a closable inlet opening is provided in the drum at a location axially spaced from its outlet aperture.

7. Apparatus according to any preceding claim, wherein the drum, drive means and burner are mounted on a wheeled chassis.

8. Apparatus according to any preceding claim, wherein the auger arrangement comprises two augers, arranged as a double start thread, on the inner surface of the drum.

9. Apparatus according to claim 8, wherein a transversely extending baffle is mounted to bridge said two augers at an axial location spaced inwardly from said outlet opening.

10. Apparatus according to any preceding claim, wherein an external pivotally mounted chute is provided adjacent the outlet opening, the chute being pivotable from an upper position in which it is inclined downwardly towards the -outlet opening to enable material to be introduced through the outlet opening and a lower position in which it is inclined downwardly away from the outlet opening to guide material discharged from the outlet opening.