Field of Invention

This invention relates to a mobile heating device having an extension with a plurality of heating torches adjustably mountable on the extension for heating a substrate. More particularly this invention relates to a mobile jet torch heating device for heating a substrate , the heating device having an extension disposed substantially parallel to the surface with a plurality of heating torches mounted for selective placement on the extension to provide a short wide substantially flat flame for heating the surface as well as the method embodied therein. Background to the Invention

There are a variety of heating devices which have been used in the prior art for heating substrates such as asphalt, concrete or the like. Such heating devices can comprise of massive machines that can be used to lay kilometres of highways to smaller machines or devices that are utilized to heat cracked asphalt to repair same or to apply thermoplastic markings to the substrate.

Since a large percentage of the worlds population live in urban areas and approximately 1/3 of the surface area of these urban regions are covered by concert or asphalt pavements, sidewalks, parking lots and the like which present a variety of environmental, safely, health and social issues, there has been a recent movement to apply markings for functional or decorative proposes to the asphalt.

For example, U.S. Patent No. 6,998,010 relates to a method and apparatus for heating a surface marking, such as thermoplastic patterns in an asphalt substrate. The markings may be selective for functional or decorative purposes. The method involves gradually applying heat to the markings to avoid scorching and to ensure a consistent bond with the underlying substrate, even in the case of markings having a very large surface area. In one embodiment of the method, a portable heating surface is provided having infrared heaters mounted for reciprocal movement in a travel path periodically passing over the marking and the underlying substrate. The heating permits a direct visual monitoring of the worksite to achieve optimal adhesion of the marking to the asphalt or other substrate. Although a method described in U.S. Patent No. 6,998,010 provides an effective way of heating a surface marking, such devise is generally large and heavy to operate, which makes it difficult to work in confined areas. It is also very complex which makes it expensive to manufacture and maintain.

There is a need for smaller, simpler, less expensive devices which can be used. Smaller devices are known in the prior art which include hand held propane jet torches which generally comprise a torch gun which are very tiring to use for the operator and are very slow and costly. Example of such torch guns can be found in U.S. Patent No. 3,779,694 which comprise hand held heat guns heated at 250 to 1000 degrees centigrade that employ high performance combustion burner discharge exhaust gases at a high speed. U.S. Patent No. 5,476,378 relates to a pressure head needed to drive combustion air into a combustion region of a heat gun having compression blades in a turbine whose blades are interposed in the fade conduit that leads to the combustion region.

Furthermore, U.S. Patent No. 6,010,329 relates to a jet pump for heat guns which includes an elongated hollow pump body lying along a horizontal axis. The pump body has an inlet, a mixing section and an outlet. The nozzle unit is actually aligned with the inlet for directing pressurized fluid into the inlet of the pump body.

These and other prior art hand held propane jet torches can cause under or over heating if not properly used that result in quality issues and are generally difficult to control.

Moreover, prior art mobile infrared heating machines have used propane-fired infrared heaters which are more expensive to purchase and maintain than the handheld propane jet torches and they are much heavier which makes operation tiring and difficult. Another problem with the mobile infrared heating machines is that they take a long time to heat up and cool down making for uneven heating in large areas. Furthermore they require a long heating area, namely longer heater bed in a direction of machine travel to provide enough heating time which makes heating uneven at the stop and start point when operating in a back and forth reciprocal motion as these heaters are commonly operated.

Accordingly, there is a need to provide an improved heating device and method for heating substrates. It is an aspect of this invention to provide a mobile heating device which comprises a portable carriage for holding heating fuel; an extension from the carriage; a plurality of heating torches selectively mounted on said extension for heating a substrate. The torches provide a short wide substantially flat flame for heating the substrate. It is another aspect of this invention to provide a mobile jet torch heating device for heating a substrate comprising a wheeled carriage having handles; a fuel tank carried by the wheeled carriage; an extension from the carriage disposed substantially parallel to the substrate; a plurality of heating torches mounted for selective placement on the extension, to provide a short wide substantially flat flame which produces hot gases for heating the substrate. Another aspect of this invention provides a method of heating a substrate comprising: gradually heating the substrate by periodically passing at least one heater in proximity to the substrate; providing heating apparatus having a support arm extending over the substrate, wherein the heating apparatus is mounted for selective placement on the support arm and the heating apparatus moved in a travel path periodically passing over the substrate. These and other features and objects of the invention shall now be described in relation to the following drawings:

Description of the Drawings

Figure 1 is the perspective view of the mobile heating device.

Figure 2 is another perspective view of the invention showing the plurality of heating torches. Figure 3 is an enlarged perspective view of the heating torch.

Figure 4 is a perspective view of the heating device utilised to apply thermoplastic markings on a surface.

Figure 5 is another perspective view showing the use of the heating devise to repair potholes. Figure 6 is a cross sectional view of an embodiment of a heating torch. Detailed Description of the Invention

Throughout the following description specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have now been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specifications and drawings are to be regarded in an illustrative rather than a restrictive sense.

Figure 1 generally illustrates the mobile heating device 10 which comprises a portable carriage 12 having wheels 14. In one embodiment, the rear wheels can be driven by a motor ( which is not shown ) although this is an optional feature. The carriage 12 is utilized to hold or carry fuel tanks, such as propane tanks 16 or other suitable fuel. Although two propane tanks were shown, one or any number of tanks may be utilized.

The carriage 12 includes an extension or support arm 18 which has a plurality of heating means or torches 20 which are mounted for selective adjustment and placement along the support arm 18. In one embodiment of the support arm 18 comprises a bar extending outwardly to one side of the carriage 12 as shown in Figure 1 along an axis X , which is generally disposed horizontally or substantially parallel to the substrate 40.

The support arm 18 includes a bracket 22 which slides along the bar 18 in a substantially parallel disposition relative to the surface or substrate 40 to be heated. The bracket 22 includes two sections , namely first hollow bracket section 22a having a substantially rectangular cross section and second hollow bracket section 22b having a substantially rectangular cross section . First hollow bracket section 22a is disposed perpendicular to second hollow bracket section 22b.

First hollow bracket section 22a slidingly receives support arm 18. This permits the plurality of torches 20 to be selectively placed along the bar 18 so that the plurality of torches produce a short flat flame.

The bracket 22 includes tightening mechanism 24 which in one embodiment comprises a lock nut at the end of a threaded stud that is threaded into the bracket 22 so as to bear against the vertical adjustment proportion 26 of the heating torches 20 as best seen on Figure 3. This permits adjustment of the heating torches 20 vertically relative to the substrate 40. Bracket 22 also includes a second tightening mechanism 25 disposed on the top part of the first hollow bracket section 22a as best seen in Figure 2 so as to secure and tighten the position of the heating torches substantially horizontally along the bar 18 relative to the surface. The second cross-section is adapted to slidingly receive the rectangular cross-section of the vertical portion 26 of the heating torches 20.This permits adjustment of the heating torches 20 vertically relative to the substrate 40.

The heating torches 20 include a combustion head 28 guard which has a plurality of holes therein as shown in Figure 3. Figure 6 shows a cross sectional view of an embodiment of a heating torch 20. The heating torch 20 has a propane orifice 25 with a venture hollow pump body 27 which is tapered slightly outwardly along the length thereof as shown and merges with the outlet 29 which has tapered sides to produce the wide narrow flame. The combustion head guard 28 covers the outlet 29 and is shaped (oblong shape as shown) on the bottom to produce a wide narrow flame. The structure shown in Figure 6 produces the hot gases to heat the substrate as described herein.

The fuel tanks 16 have the appropriate conduits 32 communicating with the heating torches 18.

The fuel tank nozzle also includes a safety stop 34 to prevent the nozzle 28 from contacting the surface or substrate.

The invention described herein includes the mounting of the propane hot air jet torches 18 onto a mobile machine 10 for the purpose of heating substrates including asphalt, concrete pavement and thermoplastic paving markings. The invention described herein can be utilized so as to produce a short wide flat flame that heats a wide area with hot gases or direct flame depending on how high the device is mounted from the surface. The torch enables the distribution of less intense heat over wider area than a standard propane torch. Accordingly, the invention described herein is lighter, more cost effective, provides better control of heating, is safer and easier to operate than alternate methods and devices as disclosed in the prior art.

Figure 4 illustrates a method of heating a substrate 40 which comprises gradually heating the substrate 40 by periodically passing at least one heater 20 in proximity to the substrate; providing heating apparatus or device 10 having a support arm 18 extending over the substrate 40 wherein the heater 20 is mounted for selective placement on the support arm 18, and moving the device in a travel path 42a, 42b periodically passing over the substrate 40.

The heating torches 20 provide a short and substantially flat flame to heat over the substrate 40.

In one embodiment the method comprises applying a thermoplastic safety marking 44 onto the substrate 40. As previously mentioned the substrate 40 may comprise of an asphalt surface. Asphalt means a paving compound for constructing roads, driveways, walkways and the like which consist of a combination of bituminous binder, such as tar, and an aggregate, such as sand or gravel. Furthermore, this substrate 40 can comprise concrete or other materials capable of binding thermoplastic markings 44. An example of markings comprise symbols such as arrows, crosshatched lines and are available for example from Flint Trading sold under the trademarks PreMark, HotTape and Traffic Patterns. The markings 44 may be selected for a functional purpose such as traffic markings or corporate logos or maybe purely decorative.

In another embodiment it important to dry the pavement prior to applying thermoplastic markings and the infrared heaters that are used are not good at drying whereas the jet torch is highly effective. Any moisture present will prevent the thermoplastic from bonding properly.

Another reason to heat pavements in this industry is to dry the pavement prior to applying water based acrylic coatings to promote good adhesion an speed drying and the device 2 is highly effective at this versus using infrared heaters which do not provide the air movement above the heated surface or substrate.

Also the device 2 could be used to dry water based acrylics once they are applied to help them dry using a jet torch raised to 12 inches about the surface which would product a 650 F hot air blast at 1200 fpm velocity, This would dry the coating quickly without overheating and damaging it.

Figure 5 also shows another embodiment of the method whereby the mobile heating device 10 can be utilized to repair potholes.

Accordingly, the plurality of heating torches 20 can be selectively mounted on the support arm 18 by utilizing the tightening mechanisms 24 described above so that the plurality of heating torches 20 are adjusted at the right height (i.e., vertically or perpendicularly relative to the support arm 18) and horizontally along the axis X of the support arm 18 so that the flame from the plurality of torches 20 produce a substantially short flat heating flame , where the heat along the flame of the torches is generally uniform (see Figure 4) to heat the substrate 40 as the user pushes and pulls on the handles 50 to gradually heat an area of the thermoplastic safety markings 44 as shown in Figure 4 so as to bond same to the substrate. In other words the torches can be adjusted so that the flame is uniform ie does not overlap each other; or if the flames overlap they overlap uniformly along the entire flame front exposed to the substrate 40.

The same method can be utilized to repair the cracked pothole so that the asphalt is heated to a sufficient temperature within a range of 100 degrees to 400 degrees Fahrenheit or a temperature sufficient to cause the cracked asphalt to become malleable and repairable. Furthermore the temperature of the plurality of heating torches can be adjusted to heat the thermoplastic safety marking to a temperature which is sufficient to heat and bond the marking to the substrate.

Depending upon the material used, markings 44 are heated in situ to temperature within a range of 100 degrees to 400 degrees Fahrenheit, or more particularly 150 degrees to 350 degrees

Fahrenheit. Optionally markings 44 and/or substrate 40 may be preheated prior to placement of the markings at the worksite.

It will be apparent to those persons skilled in the art that many alternations and modifications are possible in the practice of the invention without departing from the spirit or scope thereof. Accordingly the scope of the invention is to be construed in accordance with the substance defined by the following claims.

These and other features of the invention should not be described in relation to the following claims.