CA2621771C - Method and apparatus for applying hot mix for tar sealed roads - Google Patents
Method and apparatus for applying hot mix for tar sealed roads Download PDFInfo
- Publication number
- CA2621771C CA2621771C CA2621771A CA2621771A CA2621771C CA 2621771 C CA2621771 C CA 2621771C CA 2621771 A CA2621771 A CA 2621771A CA 2621771 A CA2621771 A CA 2621771A CA 2621771 C CA2621771 C CA 2621771C
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- Prior art keywords
- vessel
- aggregate
- shell
- bitumen
- rotor
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/08—Apparatus for transporting and heating or melting asphalt, bitumen, tar, or the like
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
- B01F27/80—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis
- B01F27/90—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis with paddles or arms
- B01F27/906—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis with paddles or arms with fixed axis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
- B01F35/90—Heating or cooling systems
- B01F35/92—Heating or cooling systems for heating the outside of the receptacle, e.g. heated jackets or burners
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
- E01C19/1013—Plant characterised by the mode of operation or the construction of the mixing apparatus; Mixing apparatus
- E01C19/104—Mixing by means of movable members in a non-rotating mixing enclosure, e.g. stirrers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F2101/00—Mixing characterised by the nature of the mixed materials or by the application field
- B01F2101/38—Mixing of asphalt, bitumen, tar or pitch or their ingredients
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Road Paving Machines (AREA)
Abstract
Apparatus is disclosed for preparing a hot mix, comprising aggregate and bitumen, for repairing pot holes in roads. A vessel (16) is mounted, vertically disposed, on a vehicle (10) and comprises a mixing chamber (42) in which the aggregate and bitumen are mixed by a paddle assembly (50) mounted on a shaft (60) that rotates about a vertical axis (X). The shaft is mounted in bearing assemblies (64, 72) located at the top and bottom of the mixing chamber. The shaft is able to slide vertically in the upper bearing assembly (72) to cope with thermal expansion as the vessel is heated during the mixing.
The vessel has a manhole (120) at its upper end (36) through which the aggregate and lumps of bitumen, at ambient temperature and hi solid form, can be loaded into the mixing chamber. The aggregate is loaded first and heated to expel moisture before the bitumen is loaded. The vessel can be tilted to discharge the hot mix through a second manhole (122) located adjacent the bottom of the mixing chamber.
The vessel has a manhole (120) at its upper end (36) through which the aggregate and lumps of bitumen, at ambient temperature and hi solid form, can be loaded into the mixing chamber. The aggregate is loaded first and heated to expel moisture before the bitumen is loaded. The vessel can be tilted to discharge the hot mix through a second manhole (122) located adjacent the bottom of the mixing chamber.
Description
TITLE: METHOD AND APPARATUS FOR APPLYING HOT MIX FOR
TAR SEALED ROADS
This invention relates to a metb.od and apparatus for applying hot mix for tar sealed roads_ BACKGROUND OF THE INVENTION
In conventional practice, the surfaces of tar-sealed roads are covered by a layer of material comprising a mix of what is known as "aggregate" and bitumen. ()yhen used in this specification, the term "mix" will refer to a mixture of these materials that is suitable for building and repairing roads, unless it is clear from the context that another meaning is intended). The aggregate comprises stone particles of various graded sizes.
If the mixing has been properly carried out, the stones are randomly dispersed in a matrix of the bitumen and the bitumen should be bonded to each stone and should cover as much of the surface of the stone as possible. It is of course nearly impossible to achieve such an ideal mix in practice but it is at least a goal that is aimed at.
At the present time when a new tar-sealed road is being conatructed, the mix is commonly prepared in bulk at a fixed facility remote from the road building site or by a large machine that is transported to, and temporarily set up, at the site:
In either case the prepared mix is transferred to a machine that lays the mix down in a continuous layer that is as wide as the road 'being built. These techniques have been developed over many decades in conj un.ction with advances in road building methods and machinery.
The machines required for building new roads in this way are large and expensive.
They are satisfactory for the construction of a new road but it would be impractical and uneconomic to use them for sinall repairs such as potholes. The repair of potholes thus presents particular problems: Potholes are, by their nature, widely spaced apart and may be many kilometres away from a facility, of the kind. discussed above, for preparing an aggregate/biturnen mix. The distance may be such that it is difficult or impossible to keep a mix that ha's been pre-prepared and transported to the site of a pothole, at the correct temperature for use. The problem is exacerbated by the fact that only a small amount of material is required for ea.ch pothole.
The bitumen and the aggregate are heated when preparing a mix. Bitumen does not flow readily at arnbienl temperature, atid it must be heated to enable it to form a good matrix for the aggregate. The aggregate is heated to drive off residual moisture but also to keep the mix fluent. It is well known that moisture interferes with the bond between the bitumen and the particles in the aggregate. The bitumen and the aggregate are usually preheated separately especially in the large scale plants of the type described above used in the preparation of mix for making new roads. After being heated,*the bitumen and the aggregate are mixed together in a mixing vessel designed for the purpose.
It is important that the mix should be at the right temperature (1.70-180 C) when it is used. It is well established that there is an optimum temperature for good bonding between the aggregate particles and the biturnen. One of the most common causes of poor road construction or a poor repair is the use of a mix that has cooled down or that still contains moisture when it is applied, as this tends to disrupt the bonding.
The applicant is aware of several mobile machines that are used in the repair of potholes. Most of these comprise a truck- or trailer-mounted insulated vessel for holding a hot mix that has been preprepared and loaded into the vessel. The apparatus may be provided wiih a small heating device, fuelled by LPG or diesel oil, for keeping the mix hot. These machines are not able to heat a bitumen mix from cold to 180 and most of them do not have any mixing devices.
The applicant is aware of two mobile machines that do have mixing devices.
However, the applicant believes that the disadvantages associated with the use of these machines, the construction and operation of which are discussed below, are such that they have not found widespread use. In any case, the applicant believes that the mix for repairing potholes is still most often prepared by methods that have been used for many years. In one such method, cornmonly used in less developed countries, the mix is prepared by hand at the site where the potholes occur. The aggregate and the bitutnezt and placed in a suitable receptacle that is heated, using a fire or other suitable heater.
The heated mix is then shovelled into a wheelbarrow or the like and taken to the pothole. In bigger jobs, the mix is prepared in a larger receptacle and loaded into a suitable truck for transport to the work site which may sometimes be perhaps 100 km distant.
Here, it is tipped or hand shovelled into the potholes. In another method, the mix comprises aggregate added to a proprietary material comprising a bituinen base and emulsifying additives which renders the material fluent at a much reduced temperature. The mix is at this reduced tenaperature when applied to the pothole.
Both of these methods have their problems. It is practically impossible to mix the materials properly by hand in the manner discussed above and the applicant believes that the use of cold mixes comprising proprietary materials of the type discussed above results in poor quality repairs. Nevertheless, they rernain in widespread use notwithstanding the availability of mobile mixing machines of the.type mentioned above.
One of the mobile machines mentioned above comprises, in essence, three vessels mounted on a trailer chassis that can be hooked on to a truck or other towing vehicle.
'I'he aggregate is heated in one of the vessels and the bitumen is heated in the second vesseL The first and second vessels arc thus heating vessels. The heated materials are transferred to the third vessel. This is a mixing vessel and in it the materials are mixed together by rotating paddles provided for the purpose. The mixing vessel is provided with a gate through which the mixed materials can be discharged by gravity into a wheelbarrow or the like.
One disadvantage of this machine is that the components that handle the bitumen, i.e.
the heating vessel, the mixing vessel and the associated pump and pipework by which the heated bitumen is transferred to the mixing vessel, must be cleaned after each use of the machine. The cleaning operation can typically take an hour or even two.
If the machine is not cleaned and the hot bitumen or hot mix has been allowed to cool in the pump and pipework or the mixing vessel, it is very laborious and time consuming to clca.r them.
Another disadvantage of this machine is that the heating vessel for the aggregate is of the type that comprises a cylindrical shell that is supported on rollers and rotates about a horizontal axis. A measured quantity of aggregate is charged through an inlet aperture formed in a plate located at one end of the shell. The aggregate is heated as the shell rotates and is discharged through an outlet aperture formed in a second plate at the opposite end of the shell. Both of the apertures have gate-type closures to retain the aggregate in the shell as it rotates. The shell is heated by burners that are located inside the shell above the aggregate. The outlet aperhue is located adjacent the bottom of the shell to allow the aggregate to flow out of the shell by gravity. The inlet aperture is located well below the top of the shell. The heated moisture forms steam and, in the applicant's experience, it is difficult for the steam to exit the shell efficiently due to the fact that the apertures are normatly closed by the gates and are located below the top of the shell. The result is that the aggregate is often not properly dry when it leaves the shell or, at best, the aggregate must be held in ttxe shell for longer than is necessary in order to ensure that it is properly dry._ In the second mobile machine known to the applicant, mentioned above, a truck is provided with a tipping body into which.a tpix that has been preprepared is tipped. The floor of the body comprises two flat surfaces that run the length of the body and slope upwardly on each side of the fore-and-aft centreline of the floor. Two heater tubes and two rotating agitator shafts are mounted in the body, running the length thereof. The shafts have screw-type flights that convey hot mix material that gravitates into their path in the fore-and-aft direction of the body and thus perform a mixing function. Hot gas from an LPG burner carried on the vehicle flows through the tubes. The body has an open top provided with covers. The body and the covers are insulated. An aperture is provided in the rear wall of the body. The hot mix is discharged through this aperture when the body is tipped.
This machine has three disadvantages. The heating arrangements are insufficient to heat a full load of mix from cold to 180 C in any practical sense and it is thus again necessary to ensure that the vessel is cleaned befoie it is allowed to cool.
Second, the agitator shafts do not perform the mixing function with any great efficiency with the result that some parts of the mix are liable to be too cold and other parts too hot. A
third disadvantage is that the bearings of the agitator shafts are liable to failure as a result of the stresses that they undergo due to the thermal expansion of the agitator shafts.
Although the mixing process is apparently simple, well-known techniques have been developed in order to achieve a good quality mix. For example, it is knoAn that the quality of the mix can be improved by adding the particles of each size in sequence to 5 a batch of aggregate that is being dried. Often the sequence is starts with the largest size and progresses to the smallest size (which is, essentially, dust). The bitumen is best added after sotne of the dust has been added and the batch is properly dry.lvlore dust can then be added to bring the mix to the right consistency. The sequence is also sometimes reversed. It is not possible, in a practical sense; to use these techniques with the mobile machines described above.
STATF:.Mf:NTS OF THE iNVENTION
According to the invention, there is provided apparatus for preparing a hot mix comprising aggregate and bitumen, the apparatus comprising a vessel incorporating a mixing chamber arranged to receive aggregate and bitumen, means for mounting the vessel on a vehicle, heating means arranged to heat the aggregate and bitumen, and mixing means for innixing the aggregate and bitumen to form a hot mix, the vessel comprising a shell and the mixing means comprising a rotor that can be mounted in the shelt for rotation about a rotational axis that is disposesi longitudinally in the shell and is arranged to carry at least one mixing member that is disposed transversely to the rotational axis and, as the rotor rotates, describes a path that substantially spans the space between the rotor and the shell.
According to one aspect of the invention, the shell is of right circular cylindrical shape and the rotational axis is coincident with.the longitudinal axis of the shell.
In. another aspect of the invention, the shell is mounted on the vehicle in a vertical disposition.
In yet another aspect of the invention, the shell comprises a cross member on which the rotor is rotatably mounted.
TAR SEALED ROADS
This invention relates to a metb.od and apparatus for applying hot mix for tar sealed roads_ BACKGROUND OF THE INVENTION
In conventional practice, the surfaces of tar-sealed roads are covered by a layer of material comprising a mix of what is known as "aggregate" and bitumen. ()yhen used in this specification, the term "mix" will refer to a mixture of these materials that is suitable for building and repairing roads, unless it is clear from the context that another meaning is intended). The aggregate comprises stone particles of various graded sizes.
If the mixing has been properly carried out, the stones are randomly dispersed in a matrix of the bitumen and the bitumen should be bonded to each stone and should cover as much of the surface of the stone as possible. It is of course nearly impossible to achieve such an ideal mix in practice but it is at least a goal that is aimed at.
At the present time when a new tar-sealed road is being conatructed, the mix is commonly prepared in bulk at a fixed facility remote from the road building site or by a large machine that is transported to, and temporarily set up, at the site:
In either case the prepared mix is transferred to a machine that lays the mix down in a continuous layer that is as wide as the road 'being built. These techniques have been developed over many decades in conj un.ction with advances in road building methods and machinery.
The machines required for building new roads in this way are large and expensive.
They are satisfactory for the construction of a new road but it would be impractical and uneconomic to use them for sinall repairs such as potholes. The repair of potholes thus presents particular problems: Potholes are, by their nature, widely spaced apart and may be many kilometres away from a facility, of the kind. discussed above, for preparing an aggregate/biturnen mix. The distance may be such that it is difficult or impossible to keep a mix that ha's been pre-prepared and transported to the site of a pothole, at the correct temperature for use. The problem is exacerbated by the fact that only a small amount of material is required for ea.ch pothole.
The bitumen and the aggregate are heated when preparing a mix. Bitumen does not flow readily at arnbienl temperature, atid it must be heated to enable it to form a good matrix for the aggregate. The aggregate is heated to drive off residual moisture but also to keep the mix fluent. It is well known that moisture interferes with the bond between the bitumen and the particles in the aggregate. The bitumen and the aggregate are usually preheated separately especially in the large scale plants of the type described above used in the preparation of mix for making new roads. After being heated,*the bitumen and the aggregate are mixed together in a mixing vessel designed for the purpose.
It is important that the mix should be at the right temperature (1.70-180 C) when it is used. It is well established that there is an optimum temperature for good bonding between the aggregate particles and the biturnen. One of the most common causes of poor road construction or a poor repair is the use of a mix that has cooled down or that still contains moisture when it is applied, as this tends to disrupt the bonding.
The applicant is aware of several mobile machines that are used in the repair of potholes. Most of these comprise a truck- or trailer-mounted insulated vessel for holding a hot mix that has been preprepared and loaded into the vessel. The apparatus may be provided wiih a small heating device, fuelled by LPG or diesel oil, for keeping the mix hot. These machines are not able to heat a bitumen mix from cold to 180 and most of them do not have any mixing devices.
The applicant is aware of two mobile machines that do have mixing devices.
However, the applicant believes that the disadvantages associated with the use of these machines, the construction and operation of which are discussed below, are such that they have not found widespread use. In any case, the applicant believes that the mix for repairing potholes is still most often prepared by methods that have been used for many years. In one such method, cornmonly used in less developed countries, the mix is prepared by hand at the site where the potholes occur. The aggregate and the bitutnezt and placed in a suitable receptacle that is heated, using a fire or other suitable heater.
The heated mix is then shovelled into a wheelbarrow or the like and taken to the pothole. In bigger jobs, the mix is prepared in a larger receptacle and loaded into a suitable truck for transport to the work site which may sometimes be perhaps 100 km distant.
Here, it is tipped or hand shovelled into the potholes. In another method, the mix comprises aggregate added to a proprietary material comprising a bituinen base and emulsifying additives which renders the material fluent at a much reduced temperature. The mix is at this reduced tenaperature when applied to the pothole.
Both of these methods have their problems. It is practically impossible to mix the materials properly by hand in the manner discussed above and the applicant believes that the use of cold mixes comprising proprietary materials of the type discussed above results in poor quality repairs. Nevertheless, they rernain in widespread use notwithstanding the availability of mobile mixing machines of the.type mentioned above.
One of the mobile machines mentioned above comprises, in essence, three vessels mounted on a trailer chassis that can be hooked on to a truck or other towing vehicle.
'I'he aggregate is heated in one of the vessels and the bitumen is heated in the second vesseL The first and second vessels arc thus heating vessels. The heated materials are transferred to the third vessel. This is a mixing vessel and in it the materials are mixed together by rotating paddles provided for the purpose. The mixing vessel is provided with a gate through which the mixed materials can be discharged by gravity into a wheelbarrow or the like.
One disadvantage of this machine is that the components that handle the bitumen, i.e.
the heating vessel, the mixing vessel and the associated pump and pipework by which the heated bitumen is transferred to the mixing vessel, must be cleaned after each use of the machine. The cleaning operation can typically take an hour or even two.
If the machine is not cleaned and the hot bitumen or hot mix has been allowed to cool in the pump and pipework or the mixing vessel, it is very laborious and time consuming to clca.r them.
Another disadvantage of this machine is that the heating vessel for the aggregate is of the type that comprises a cylindrical shell that is supported on rollers and rotates about a horizontal axis. A measured quantity of aggregate is charged through an inlet aperture formed in a plate located at one end of the shell. The aggregate is heated as the shell rotates and is discharged through an outlet aperture formed in a second plate at the opposite end of the shell. Both of the apertures have gate-type closures to retain the aggregate in the shell as it rotates. The shell is heated by burners that are located inside the shell above the aggregate. The outlet aperhue is located adjacent the bottom of the shell to allow the aggregate to flow out of the shell by gravity. The inlet aperture is located well below the top of the shell. The heated moisture forms steam and, in the applicant's experience, it is difficult for the steam to exit the shell efficiently due to the fact that the apertures are normatly closed by the gates and are located below the top of the shell. The result is that the aggregate is often not properly dry when it leaves the shell or, at best, the aggregate must be held in ttxe shell for longer than is necessary in order to ensure that it is properly dry._ In the second mobile machine known to the applicant, mentioned above, a truck is provided with a tipping body into which.a tpix that has been preprepared is tipped. The floor of the body comprises two flat surfaces that run the length of the body and slope upwardly on each side of the fore-and-aft centreline of the floor. Two heater tubes and two rotating agitator shafts are mounted in the body, running the length thereof. The shafts have screw-type flights that convey hot mix material that gravitates into their path in the fore-and-aft direction of the body and thus perform a mixing function. Hot gas from an LPG burner carried on the vehicle flows through the tubes. The body has an open top provided with covers. The body and the covers are insulated. An aperture is provided in the rear wall of the body. The hot mix is discharged through this aperture when the body is tipped.
This machine has three disadvantages. The heating arrangements are insufficient to heat a full load of mix from cold to 180 C in any practical sense and it is thus again necessary to ensure that the vessel is cleaned befoie it is allowed to cool.
Second, the agitator shafts do not perform the mixing function with any great efficiency with the result that some parts of the mix are liable to be too cold and other parts too hot. A
third disadvantage is that the bearings of the agitator shafts are liable to failure as a result of the stresses that they undergo due to the thermal expansion of the agitator shafts.
Although the mixing process is apparently simple, well-known techniques have been developed in order to achieve a good quality mix. For example, it is knoAn that the quality of the mix can be improved by adding the particles of each size in sequence to 5 a batch of aggregate that is being dried. Often the sequence is starts with the largest size and progresses to the smallest size (which is, essentially, dust). The bitumen is best added after sotne of the dust has been added and the batch is properly dry.lvlore dust can then be added to bring the mix to the right consistency. The sequence is also sometimes reversed. It is not possible, in a practical sense; to use these techniques with the mobile machines described above.
STATF:.Mf:NTS OF THE iNVENTION
According to the invention, there is provided apparatus for preparing a hot mix comprising aggregate and bitumen, the apparatus comprising a vessel incorporating a mixing chamber arranged to receive aggregate and bitumen, means for mounting the vessel on a vehicle, heating means arranged to heat the aggregate and bitumen, and mixing means for innixing the aggregate and bitumen to form a hot mix, the vessel comprising a shell and the mixing means comprising a rotor that can be mounted in the shelt for rotation about a rotational axis that is disposesi longitudinally in the shell and is arranged to carry at least one mixing member that is disposed transversely to the rotational axis and, as the rotor rotates, describes a path that substantially spans the space between the rotor and the shell.
According to one aspect of the invention, the shell is of right circular cylindrical shape and the rotational axis is coincident with.the longitudinal axis of the shell.
In. another aspect of the invention, the shell is mounted on the vehicle in a vertical disposition.
In yet another aspect of the invention, the shell comprises a cross member on which the rotor is rotatably mounted.
Advantageously, according to the invention, the cross member is located at wbat, in use, is the lower end of the mixing chamber.
In one form of the invention, the rotor comprises a rotatable shaft and the apparatus 5. comprises a bearing arrangement that is mounted on the cross meritber ain.d in which an end of the shaft rotates, In one aspect of the invention, the bearing arrangement comprises an opening such that material from the mixing chamber that passes between the shaft and the bearing arrangement can pass back into the mixing chamber.
In one form of the invention, the apparatus comprises a drive arrangement for rotating the rolor, the drive arrangement comprising a driven rotary member in which is forned a passage through which the rotor projects, the passage and the rotor being eomplemen.tarily out-of-round so that the rotor is able to slide axially in the passage while being driven by the rotary member.
According to yet another aspect of the invention, the vessel is mounted so as to be stationary on the vehicle when the aggregate and bitumen are being heated and mixed.
Advantageously, according to the invention, the vessel comprises a second chamber located adjacent the mixing chamber, the heating means being located in the second chamber.
It is envisaged that the vessel could be mounted on a vehicle that is self propelled or that is in the forin of a trailer that is towed by second vehicle. The trailer would.
advantageously be provided with an engine or other means for powering the mixer and tilting mechanism.
The intended use of the apparatus has important effects on variuus aspects of its design. A vital feature of the apparatus is that it should be able to transport the mix from a locality at which the vessel is charged with the ingredients of the mix and'the work site where the mix is discharged. It is highly unlikely that the use of public roads could be avoided in this task and the size of both the vehicle and the vessel will be at least partially determined by tlus, since the size of any vehicle that uses a public road is limited by regulation. Furthernio'rc, the apparatus is intended primarily for use in repairing roads, rather than for building new roads, although a vehicle for the latter purpose is not necessarily excluded from the scope of the iunvention.
Consequently, it is highly desirable that the vehicle sbould be very manoeuvrable at the work site and this will also affect the size of the vehicle, the length of its wheelbase and the like.
Furthermore, again because of the primary intended use of the vehicle, the heating means should advantageously be designed to heat the ingredients from the ambient to the minimum mixing temperature in a reasonably short period of time that is affected at least partially by the time taken for the vehicle to transport the load from. the locality at which the vessel is charged with the ingredients of the mix to the work site where the mix is discharged. The maximum kW output of the heater will therefore need to be relatively large, and this maximum will increase with the volume of the ingredients .
that the vessel is capable of holding. However, both the maximum heat output and the volume of ingredients vvill be liinited by the size of the vehicle, as already noted.
A detailed description is given below of a vessel mounted on a vehicle that are both considered, at the present time, to be of optimum size. The sizes given are merely examples and there is no intention that the scope of the invention should be limited to a vehicle and vessel of these sizes. The vessel in the example is smaller than the maximum presently envisaged according to the invention or the maximum as deternnined by the parameters discussed above. One reason for this difference in sizes is that, as should be obvious, as the apparatus gets bigger, it also becomes more expensive and less manoeuvrable. The size of the necessary heater also increases and it may become more difficult to provide a heater with suff'icient output to heat the mix in a reasonable time., So the overall usefulness of a larger vehicle and vessel may be diminished.
The applicant believes that the road regulations in most countries would limit the volume of the vessel to about 8 cubic metres and that a heater for heating the charge in a vessel of this size would be of tiie order of 200kW. In the exarnple of the invention given below, the appara.tus is provided with a gas heater with an output of about 75kW. This is considered sufficient to heat a mix having a volume of about 0.7 cubic metres. Although not to be excluded from the scope of the invention, it is considered unlikely, at the present time, that apparatus constructed according to the precepts of the invention and requiring a heater of 200 kW output would be cornmercially or practically viable, at least for repair work on roads as opposed to the building of new roads. At least one reason for this is that it is likely to be difficult and expensive to design a vehicle which would be practical to operate, and which would not be damaged by the heat radiated by an apparatus of this size It is also likely that apparatus that is constructed and used in accordance with the present invention but that is of less than a certain capacity will be uneconomic to operate_ For instance, an apparatus that is of smaller size than that described with reference to the drawings should not necessarily be excluded from the scope of the invention.
The smallest and largest size of an apparatus that has comrnercial value will be determined by demand in the market place.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further discussed with reference to the accompanying drawings in which a vehicle for use in road repair. is illustrated by way of example, and in which Figure 1 is a somewhat schematic side elevation, partly in section, of a vehicle fitted with a vessel for preparing a road mix;
Figure 2 is a plan view of the vehicle also partly in section of the vehicle shown in Figure 1;
Figures 3 and 4 are enlarged sectional views of two bearing arrangements with-which the vessel is provided;
Figure 5 is a view on arrows A-A- in Figure 4; and Figure 6 is a view in elevation of a paddle ann In the description that follows, only those parts of the vehicle and vessel that are relevant to the present invention will be described in detail. Furthermore, the design and construction of many parts of the vehicle and vessel are either known or would present no difficulty to those skilled in the art. In some cases, these parts are commercially available. Parts that are not sliown in the drawings fall into these categories unless it appears otherwise from the context.
Referring to the drawings, there is shown a vehicle 10 having a pair of front wheels 12 and a pair of rear wheels 14. The vehicle is propelled by the front wheels and steered by the rear wheels. A vessel 16 is mounted on the front of the vehicle 10. The vehicle comprises a chassis or frame 18 on which is mounted an engine 20 housed in a bonnet 22. In the present example, the engine is a diesel engine of 34 h.p. The engine is located at the rear of the vehicle and is coupled to a hydraulic pump assembly 24. A
seat 26 for the driver is mounted to one side of the engine_ The driver thuS
sits at the rear of the vehicle, facing forward in an optimum position to view the operation of the vessel. As no cab is provided, the driver sits in the open, behind a steering wheel 28 supported by a bracket 30. The_vehicle in this example is about 3.3 metres long and 2.0 metres wide.
The vessel 16 comprises an inner steel shel132 with a right circular cylindrical body and, atits upper end, a dome shaped cross member that will be referred to as the top wail 36. A cylindrical outer shel138 surrounds the inner shell with a space therebetween forming an annular passage 40 between the two shells. The shell incorporates an upper chamber 42 that in use functions as a mixing chamber in which aggregate and bitumen are.mixed together, as will be desciibed. The upper chamber is separated from a second, lower, chamber 44 by a floor comprised of two dome shaped -cross members that will be referred to as cross walls 46, 481ocated one above the other. Mixing means is the form of rotor comprisi.ng a paddle assembly 50 mounted on a shaft 60 is located in the upper chamber and heating means in the form, in this case, of a=gas ring 52 is located in the lower chatnber, suppoA-#ed by a cross member 54.. In the lower chamber, apertures 56 are formed in the wall of the shell 32. Via the annular passage 40, the apertures connect the lower chambei to chimneys 58 spaced around the domed top 36.
The paddle assembly 50 comprises a pair of mixing members in the form of paddle arms 50a, 50b. The paddle arms are mounted in alignment with each other on opposite sides of the shaft 60, which is of square cross section. The shaft is disposed longitudinally the shell. The shaft is carried in bearing arra-ngements mounted on the upper cross wall 46 and in the top wall 36 respectively and rotates about a rotational axis X that is coincident with the longitudinal axis of the shell that, in the present 5 example, is vertical.
The upper end 60a of the shaft projects through a drive arrangement 62 that, in this exatnple, corriprises a driven rotary member in the form of a gear wheel 66 driven by a worm. The worm is coupled to a hydraulic motor 70 driven, through suitable hydraulic 10 lines and controls to the pump assembly 24. The gear wheel 66 is integral with the outer race 72a of a roller bearing assembly 72 the inner race 72b of which is bolted to tlie floor of the gearbox housing 74. The gearbox in turn is bolted to'the top of a pedestal assembly 36a that is mounted on the top wal136 of the vessel. The outer race is bolted to a circular collar plate 76. The bearing assembly 72 and the collar plate are parts of the upper bearing arrangement for the shaft 60. The collar plate is provided with a central passage 78 that is of square cross sectional shape of size complemental to the shaft 60 and such I.hat, when the gear wheel rotates, the collar plate engages the shaft, forciiig it to rotate also. However the s.haft is also able to slide up and down in an axial direction in the passage 78. This is important as the sha.ft undergoes considerable such axial movement up and down as the apparatus heats up and cools down. This axial movement is as much as 30 mm in the present example. It is not essential that the shaft 60 and lhe passage 78 be of square cross sectional shape but this shape is probably the most practical. Any suitable out-of-round shape could be used.
The lower end 60b of the shaft is machined so that it is round and is received in the lower bearing arcangement 64. This arrangement comprises a vertically disposed sleeve 80 that in use functions as a bearing bush for the lower end of the shaft. The sleeve is supported above the cross wa1146 on four legs 82 that are welded to the sleeve and to the~ cross walI 46. The legs are equally spaced about the periphery of the sleeve. There is thus a space 84 between ihe lower end of the sleeve and the cross wall and there are gaps 86 betweeTi each pair of the legs. Additionally, openings in the form of vertical slits 88 are formed in the lower end of the sleeve 80. These slits are open to the gaps 86 between the legs 82.
In use, material firom the aggregate and bitumen that is being mixed in the mixing chamber migrates, principally under the force of gravity, between the lower end 60b of the shaft and the sleeve 80. It has been found that this material has a tendency to build up in the sleeve and, in the absence of means to prevent it, eventually causes the shaft to seize. The build up is prevented by the presence of the space 84 and the slits 88 which function as openings through which the material is able to exit the sleeve through the gaps 86 and back into the mixing chamber.
In the present example the diameter of the lower end of the shaft is about 58 mm and the internal diameter of the sleeve 80 is about 61 mm. There is thus considerable clearance therebetween. This is necessary to accommodate the considerable ehatiges in size of the components due to thermal expansion and contraction. It has been found in practice that, at it's centre, the cross wall 46 is typically lifted by about 30 .mrn due to thennal expansion as it heats up to working temperature.
The paddle arms 50a, 50b that are similar to each other and only one is described in detail. The ann 50a is fabricated from a steel plate 98, tapered inwardly from its inner end to its outer end and reinforced by a rib 100 that is welded to the approxiniate centre of the face 102 of the plate and runs along the entire length thereof_ At its inner end, the plate 98 is welded to an upstanding rectangular mounting plate 104 with boltholes drilled in each corner. The paddle arms are mounted on the shaft 60 by means of bolts 108 that pass through the holes and clamp the respective mounting plates against opposite faces of the shaft. Two upstanding paddle plates 110a, 110b of approximately trapezoidal shape are welded to the face'i 12 of the plate 98.
Wearing shoes 114 may be welded to the lower edges of the respective paddle plates_ The width of each paddle plate is about a quarter of the length of the plate 98. The paddle plates 11 0a, I I Ob on the arm 50a aremounted on the plate 98 with a space 116 between them approximately equal to the width of each paddle plate. The paddle plate l 10a is mounted at the outer end of the plate 98. The space 118 between the paddle plate 1.10b and the mounting plate 104 is thus again approxi.mately equal to the width of each paddle plate.
The paddle arm 50b is substantially simila.r to tlie paddle arm 50a with the exception of the positioning of the pa.ddle plates. While the paddle plates of the arm 50b are also lz mounted with a space 116a between them approximately equal to the width of each paddle plate, the inner paddle plate of the arm 50b is located close to the mounting plate 104 of that arm. The result of this arrangement is that, when the shafl.
60 is rotated, the paddle plates between them sweep the entire diameter of the shell 32 and the cross wall 46. The paddle plates are shaped and mounted on the arms 50a, 50b in such positions that the wearing shoes are located close to, and parallel with, the domed upper cross wall 46. The outer ends of the paddle arms are located close to the inner face of the shell 32.
As the rotor rotates, each paddle arm thus sweeps through a path that substantially spans the space between rotor and the shell 32. Furthernlore, the path swept by the paddle arms jointly is substantially coincident with the upper surface of shell floor.
The tops of the paddle plates are located close to the top of a full load of aggregate in the mixing chamber. Virtually all of the load is thius subject to the mixing action of the paddle assembly during each revolution of the rotor and the mixing acEion is thus highly efficient. This action is most efficient when the shell is right circular cylindrical.
A shell of this shape is also likely to be the most economical to produce.
However, shells of other shapes are not necessarily excluded from the scope of the invention.- A
shell of square shape could also conceivably be used. In this case, the path swept by the paddle atms would best span the smallest space between the rotor and each vertical wall of the shell. This space would extend between the rotor and the centre of the vertical wall.
An aperture in the form of a manhole 120 is provided at the ft-oni. of the domed top wall 36. Aggregate and lumps of bitumen in solid condition are shovelled into the upper chaniber through this manhole, as will be described.
Discharge means are provided in the form, in the present example, of a closable aperture or manhole 122 is provided low down at the front of the shell, adjacent the upper cross wall 46. The manhole is closed by a manually operated, guillotine type gate 124. A chute 126 is mounted adjacent the manbole 122. VJhen the aggregate and bitumen have been properly mixed and heated to the correct temperature in the upper chamber, the mix can be.discharged through the manhole and onto the chute.
The heater 52 is a two ringed gas burner fed from twin gas cylinders 128 through suitable hoses. Zn the present example, the heat output 'of the burner is of the order of 75 kVd, as already noted. The domed shape helps to prevent thermal distortion of the cross walls 46, 48. Notwithstanding the domed shape, in the absence of the lower cross wali 48, the heat from the burner would be likely to overheat the upper cross wall 46, causing it to distort. The two cross walls are located close together in order to maximise heat transfer and the presence of the lower cross wal148 helps to spread the heat and avoid hot spots in the upper cross wa1146.
A layer 130 of suitable insulating material is placed around the outside of the shell 38 to reduce heat loss. The insulating material is held in place and protected by a steel sheU 132. The hot gases from the bumer pass through the apertures 56 in the shell 32 and out through the chimneys 58 via the annular passage 40_ These gases heat the wall of the shell 32 and the heat is transferred to the mix in the upper chamber.
The vessel 16 is mounted on the frame 18 so as to be capable of tilting forward about a hinged connection 134 located at the front edge of the frame. The tilting is brought about by a hydraulic ram 136. The lower end of the ram is mounted on the fxame through a pin seated between trunnions 138 welded to the frame. The upper end of the ram is similarly mounted on the vessel through a pin seated between trunnions welded to the shell 38. The ram is actuated by the driver through suitable controls, not shown. As should be clear, the vcssel remains stationary on the frame while the aggregate and bitumen are being heated arid mixed.
A safety barrier may be monnted on the fr6nt of the vehicle, surrounding the front of the vessel 16. The barrier comprises a series of steel stanchions 144 welded to the frame 18 at their lower ends and carrying rails 146 welded to their upper ends. The barrier is intended primarily to prevent damage to the vessel in the event that the -vehicle collides with objects around a work place. One example af such an object is the back of a delivery vehicle that carries aggregate and/or raw bitumen. It would often be convenient to shovel the aggregate or bitunen directly into the vessel from the delivery vehicle and the two vehicles would be brought together for the purpose.
The vehicle is obviously provided with the controls necessary for its operation. These controls would include a temperature gauge, visible from the driver's seat, for checking the temperature of the i ix; and a regulator for controlling the flow of gas to the burner.
In use, stocks of raw bitumen and stones for aggregate are brought to a convenient place in the vicinity of wherc there are potholes in a tar-sealed road. For practical purposes, raw bitumen is solid at ambient temperature and the bituunen in the stock is broken into lumps that can pass through the manhole 120. The stones should advantageously, but not essentially, be graded according to their size and left in separate stockpiles. All this is well known to experieneed operators. The vehicle 10 illustrated in the drawings has a maximum tra.velling speed of about 12 km/h.
This would be one of the factors that would determine how far away the stockpiles can be from the furthest pot hole that must be repaired. If the travelling speed renders the working range of the vehicle unacceptably low, the vehicle 10 can be carried to the work place on the back of a truck or trailer capable of a higher speed. An alternative exarnple of an apparatus according to the invention would be a vessel similar to the vessel 16 rnounted directly on a vehicle in the form of a trailer that is towed by a second vehicle. This second vehicle could be a cornmercial.ly available truck and would usually be capable of a much higher speed than 12 km/h.
The vehicle 10 is taken to the stockpiles where, in one method of use, first the aggregate is loaded into the upper chamber 42 through the manhole 120, while the muxer 50 is rotating and the burner lit. An experi.enced operator will know the sequence in which the material should loaded. This has been discussed above.
Such an operator will also know how long mixing and heating of the aggregate should be continued. Mixing is continued until the mixed aggregate is dry and has been brought up to the correct temperature. At this stage lumps of solid bitumen, conveniently at ambient temperature, are loaded by hand through the manhole 120. When the bitumen has melted and is well mixed with the aggregate, a further small quantity of dust may be added to bring the rnix to the correct consistency for use.
It should be stressed that, instead of loading one grade of aggregate after the other, it is possible to use a premixed composition of several aggregate sizes and dust and then add the bitumen. It is also possible, instead of adding the bitumen in solid (cold) form, it can be added in preheated, liquid form.
It is an advantageous feature of the present inverition that the matnhole 120 is located 5 close to the top'of the vessel. This enables substantially all of the moisture driven off the aggregate to escape to atmosphere as efficiently and quickly as possible.
This feature is made possible by the fact that the vessel is stationary in use.
Based on these parameters, the vessel and the shaft are most suitably vertically, or at least uprightly, disposed.
The mixer 50 continues to rotate while the vehicle is driven or taken to a selected one of the potholes to be repaired. The burner remains lit to keep the mix at the correct temperature. At the work site, the driver manoeuvres the vehicle so that the chute 126 is over the selected pothole and actuates the ram 136 to tilt the vessel 16 upwards and.
forwards about the hinge 134. A second operator lifts the gate 124 to allow the required amount of hot mix to flow out of the vessel and over the chute from where it ,=t is deposited in the pothole. The driver returns the vessel to the upright positiozi and backs the vehicle away from the pothole. The hot mix in the selected pothole is worked in known manner to complete the repair.
In the present example, the i.nternal diameter of the shell 32 is 126 cm. The vertical distance between the upper cross plate 40 and the domed top 36 is 75 cm, and the distance from the bottom of the shell to the upper cross plate 40 is 30 cm.
These dimensions are taken at the centre of the shell. The volume of the upper chamber 36 is thus about 930 litres. This is su.ff-icient for a charge of about 700 litres of aggregate and bitumen. The width of the annular passage 40 is 30 mm and the distance between the shell 38 and the shell 132 is 60 mm. The wall thicknesses of the shells 32, 38 and 132 are 6, 3 and I mm respe3ctiveiy. The overall diameter of the vessel is thus about,156 cm. This is less than the maximum width of the vehicle 10. The highest point on the vehicle, with the vessel mounted in place, is at the top of the vessel and is about 203 cm above the road surface: The vehicle is thus well within the height.and width limits for vehicles to be allowed on the public roads of most countries without a special permit.
The manhole 120 for filling the vessel is about 177 cm above the ground and the manhole 122 through ~Nrhich the mix is discharged is about 73 cm above the ground.
There is no serious disadvantage in allowing any mix remaining in the mixing chamber when a job is eompleted to cool and become solid as the mix can be made fluent again simply by heating. There is no pump or pipework to be cleaned at the end of a shift and, if necessary, the mixing chamber can easily be cleared by working through the manholes.
It may be noted that the machines consiructed according to the precepts of the invention can be used to heat bitumen only or bitumen mixed with quarry dust in a certain percentage to repair, fill or seal cracks in the bitu.men.layer.of roads to prevent water from destabilizing the roadbase. The same machines can also be used to seal roofs, expansion gaps in concirete roads and slabs.
It is not intended that -xecognised mechanical equivale.nts of and/or modifications of and/or improvements to any matter described and/or illustrated herein should be excluded from the scope of.a patent granted in pursuance of any application of which this specification forms a part or that claims the priority thereof or that the scope of any such patent should be limited by such rnatter further than is necessary to distinguish inventive matter disclosed herein from the prior art.
In one form of the invention, the rotor comprises a rotatable shaft and the apparatus 5. comprises a bearing arrangement that is mounted on the cross meritber ain.d in which an end of the shaft rotates, In one aspect of the invention, the bearing arrangement comprises an opening such that material from the mixing chamber that passes between the shaft and the bearing arrangement can pass back into the mixing chamber.
In one form of the invention, the apparatus comprises a drive arrangement for rotating the rolor, the drive arrangement comprising a driven rotary member in which is forned a passage through which the rotor projects, the passage and the rotor being eomplemen.tarily out-of-round so that the rotor is able to slide axially in the passage while being driven by the rotary member.
According to yet another aspect of the invention, the vessel is mounted so as to be stationary on the vehicle when the aggregate and bitumen are being heated and mixed.
Advantageously, according to the invention, the vessel comprises a second chamber located adjacent the mixing chamber, the heating means being located in the second chamber.
It is envisaged that the vessel could be mounted on a vehicle that is self propelled or that is in the forin of a trailer that is towed by second vehicle. The trailer would.
advantageously be provided with an engine or other means for powering the mixer and tilting mechanism.
The intended use of the apparatus has important effects on variuus aspects of its design. A vital feature of the apparatus is that it should be able to transport the mix from a locality at which the vessel is charged with the ingredients of the mix and'the work site where the mix is discharged. It is highly unlikely that the use of public roads could be avoided in this task and the size of both the vehicle and the vessel will be at least partially determined by tlus, since the size of any vehicle that uses a public road is limited by regulation. Furthernio'rc, the apparatus is intended primarily for use in repairing roads, rather than for building new roads, although a vehicle for the latter purpose is not necessarily excluded from the scope of the iunvention.
Consequently, it is highly desirable that the vehicle sbould be very manoeuvrable at the work site and this will also affect the size of the vehicle, the length of its wheelbase and the like.
Furthermore, again because of the primary intended use of the vehicle, the heating means should advantageously be designed to heat the ingredients from the ambient to the minimum mixing temperature in a reasonably short period of time that is affected at least partially by the time taken for the vehicle to transport the load from. the locality at which the vessel is charged with the ingredients of the mix to the work site where the mix is discharged. The maximum kW output of the heater will therefore need to be relatively large, and this maximum will increase with the volume of the ingredients .
that the vessel is capable of holding. However, both the maximum heat output and the volume of ingredients vvill be liinited by the size of the vehicle, as already noted.
A detailed description is given below of a vessel mounted on a vehicle that are both considered, at the present time, to be of optimum size. The sizes given are merely examples and there is no intention that the scope of the invention should be limited to a vehicle and vessel of these sizes. The vessel in the example is smaller than the maximum presently envisaged according to the invention or the maximum as deternnined by the parameters discussed above. One reason for this difference in sizes is that, as should be obvious, as the apparatus gets bigger, it also becomes more expensive and less manoeuvrable. The size of the necessary heater also increases and it may become more difficult to provide a heater with suff'icient output to heat the mix in a reasonable time., So the overall usefulness of a larger vehicle and vessel may be diminished.
The applicant believes that the road regulations in most countries would limit the volume of the vessel to about 8 cubic metres and that a heater for heating the charge in a vessel of this size would be of tiie order of 200kW. In the exarnple of the invention given below, the appara.tus is provided with a gas heater with an output of about 75kW. This is considered sufficient to heat a mix having a volume of about 0.7 cubic metres. Although not to be excluded from the scope of the invention, it is considered unlikely, at the present time, that apparatus constructed according to the precepts of the invention and requiring a heater of 200 kW output would be cornmercially or practically viable, at least for repair work on roads as opposed to the building of new roads. At least one reason for this is that it is likely to be difficult and expensive to design a vehicle which would be practical to operate, and which would not be damaged by the heat radiated by an apparatus of this size It is also likely that apparatus that is constructed and used in accordance with the present invention but that is of less than a certain capacity will be uneconomic to operate_ For instance, an apparatus that is of smaller size than that described with reference to the drawings should not necessarily be excluded from the scope of the invention.
The smallest and largest size of an apparatus that has comrnercial value will be determined by demand in the market place.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further discussed with reference to the accompanying drawings in which a vehicle for use in road repair. is illustrated by way of example, and in which Figure 1 is a somewhat schematic side elevation, partly in section, of a vehicle fitted with a vessel for preparing a road mix;
Figure 2 is a plan view of the vehicle also partly in section of the vehicle shown in Figure 1;
Figures 3 and 4 are enlarged sectional views of two bearing arrangements with-which the vessel is provided;
Figure 5 is a view on arrows A-A- in Figure 4; and Figure 6 is a view in elevation of a paddle ann In the description that follows, only those parts of the vehicle and vessel that are relevant to the present invention will be described in detail. Furthermore, the design and construction of many parts of the vehicle and vessel are either known or would present no difficulty to those skilled in the art. In some cases, these parts are commercially available. Parts that are not sliown in the drawings fall into these categories unless it appears otherwise from the context.
Referring to the drawings, there is shown a vehicle 10 having a pair of front wheels 12 and a pair of rear wheels 14. The vehicle is propelled by the front wheels and steered by the rear wheels. A vessel 16 is mounted on the front of the vehicle 10. The vehicle comprises a chassis or frame 18 on which is mounted an engine 20 housed in a bonnet 22. In the present example, the engine is a diesel engine of 34 h.p. The engine is located at the rear of the vehicle and is coupled to a hydraulic pump assembly 24. A
seat 26 for the driver is mounted to one side of the engine_ The driver thuS
sits at the rear of the vehicle, facing forward in an optimum position to view the operation of the vessel. As no cab is provided, the driver sits in the open, behind a steering wheel 28 supported by a bracket 30. The_vehicle in this example is about 3.3 metres long and 2.0 metres wide.
The vessel 16 comprises an inner steel shel132 with a right circular cylindrical body and, atits upper end, a dome shaped cross member that will be referred to as the top wail 36. A cylindrical outer shel138 surrounds the inner shell with a space therebetween forming an annular passage 40 between the two shells. The shell incorporates an upper chamber 42 that in use functions as a mixing chamber in which aggregate and bitumen are.mixed together, as will be desciibed. The upper chamber is separated from a second, lower, chamber 44 by a floor comprised of two dome shaped -cross members that will be referred to as cross walls 46, 481ocated one above the other. Mixing means is the form of rotor comprisi.ng a paddle assembly 50 mounted on a shaft 60 is located in the upper chamber and heating means in the form, in this case, of a=gas ring 52 is located in the lower chatnber, suppoA-#ed by a cross member 54.. In the lower chamber, apertures 56 are formed in the wall of the shell 32. Via the annular passage 40, the apertures connect the lower chambei to chimneys 58 spaced around the domed top 36.
The paddle assembly 50 comprises a pair of mixing members in the form of paddle arms 50a, 50b. The paddle arms are mounted in alignment with each other on opposite sides of the shaft 60, which is of square cross section. The shaft is disposed longitudinally the shell. The shaft is carried in bearing arra-ngements mounted on the upper cross wall 46 and in the top wall 36 respectively and rotates about a rotational axis X that is coincident with the longitudinal axis of the shell that, in the present 5 example, is vertical.
The upper end 60a of the shaft projects through a drive arrangement 62 that, in this exatnple, corriprises a driven rotary member in the form of a gear wheel 66 driven by a worm. The worm is coupled to a hydraulic motor 70 driven, through suitable hydraulic 10 lines and controls to the pump assembly 24. The gear wheel 66 is integral with the outer race 72a of a roller bearing assembly 72 the inner race 72b of which is bolted to tlie floor of the gearbox housing 74. The gearbox in turn is bolted to'the top of a pedestal assembly 36a that is mounted on the top wal136 of the vessel. The outer race is bolted to a circular collar plate 76. The bearing assembly 72 and the collar plate are parts of the upper bearing arrangement for the shaft 60. The collar plate is provided with a central passage 78 that is of square cross sectional shape of size complemental to the shaft 60 and such I.hat, when the gear wheel rotates, the collar plate engages the shaft, forciiig it to rotate also. However the s.haft is also able to slide up and down in an axial direction in the passage 78. This is important as the sha.ft undergoes considerable such axial movement up and down as the apparatus heats up and cools down. This axial movement is as much as 30 mm in the present example. It is not essential that the shaft 60 and lhe passage 78 be of square cross sectional shape but this shape is probably the most practical. Any suitable out-of-round shape could be used.
The lower end 60b of the shaft is machined so that it is round and is received in the lower bearing arcangement 64. This arrangement comprises a vertically disposed sleeve 80 that in use functions as a bearing bush for the lower end of the shaft. The sleeve is supported above the cross wa1146 on four legs 82 that are welded to the sleeve and to the~ cross walI 46. The legs are equally spaced about the periphery of the sleeve. There is thus a space 84 between ihe lower end of the sleeve and the cross wall and there are gaps 86 betweeTi each pair of the legs. Additionally, openings in the form of vertical slits 88 are formed in the lower end of the sleeve 80. These slits are open to the gaps 86 between the legs 82.
In use, material firom the aggregate and bitumen that is being mixed in the mixing chamber migrates, principally under the force of gravity, between the lower end 60b of the shaft and the sleeve 80. It has been found that this material has a tendency to build up in the sleeve and, in the absence of means to prevent it, eventually causes the shaft to seize. The build up is prevented by the presence of the space 84 and the slits 88 which function as openings through which the material is able to exit the sleeve through the gaps 86 and back into the mixing chamber.
In the present example the diameter of the lower end of the shaft is about 58 mm and the internal diameter of the sleeve 80 is about 61 mm. There is thus considerable clearance therebetween. This is necessary to accommodate the considerable ehatiges in size of the components due to thermal expansion and contraction. It has been found in practice that, at it's centre, the cross wall 46 is typically lifted by about 30 .mrn due to thennal expansion as it heats up to working temperature.
The paddle arms 50a, 50b that are similar to each other and only one is described in detail. The ann 50a is fabricated from a steel plate 98, tapered inwardly from its inner end to its outer end and reinforced by a rib 100 that is welded to the approxiniate centre of the face 102 of the plate and runs along the entire length thereof_ At its inner end, the plate 98 is welded to an upstanding rectangular mounting plate 104 with boltholes drilled in each corner. The paddle arms are mounted on the shaft 60 by means of bolts 108 that pass through the holes and clamp the respective mounting plates against opposite faces of the shaft. Two upstanding paddle plates 110a, 110b of approximately trapezoidal shape are welded to the face'i 12 of the plate 98.
Wearing shoes 114 may be welded to the lower edges of the respective paddle plates_ The width of each paddle plate is about a quarter of the length of the plate 98. The paddle plates 11 0a, I I Ob on the arm 50a aremounted on the plate 98 with a space 116 between them approximately equal to the width of each paddle plate. The paddle plate l 10a is mounted at the outer end of the plate 98. The space 118 between the paddle plate 1.10b and the mounting plate 104 is thus again approxi.mately equal to the width of each paddle plate.
The paddle arm 50b is substantially simila.r to tlie paddle arm 50a with the exception of the positioning of the pa.ddle plates. While the paddle plates of the arm 50b are also lz mounted with a space 116a between them approximately equal to the width of each paddle plate, the inner paddle plate of the arm 50b is located close to the mounting plate 104 of that arm. The result of this arrangement is that, when the shafl.
60 is rotated, the paddle plates between them sweep the entire diameter of the shell 32 and the cross wall 46. The paddle plates are shaped and mounted on the arms 50a, 50b in such positions that the wearing shoes are located close to, and parallel with, the domed upper cross wall 46. The outer ends of the paddle arms are located close to the inner face of the shell 32.
As the rotor rotates, each paddle arm thus sweeps through a path that substantially spans the space between rotor and the shell 32. Furthernlore, the path swept by the paddle arms jointly is substantially coincident with the upper surface of shell floor.
The tops of the paddle plates are located close to the top of a full load of aggregate in the mixing chamber. Virtually all of the load is thius subject to the mixing action of the paddle assembly during each revolution of the rotor and the mixing acEion is thus highly efficient. This action is most efficient when the shell is right circular cylindrical.
A shell of this shape is also likely to be the most economical to produce.
However, shells of other shapes are not necessarily excluded from the scope of the invention.- A
shell of square shape could also conceivably be used. In this case, the path swept by the paddle atms would best span the smallest space between the rotor and each vertical wall of the shell. This space would extend between the rotor and the centre of the vertical wall.
An aperture in the form of a manhole 120 is provided at the ft-oni. of the domed top wall 36. Aggregate and lumps of bitumen in solid condition are shovelled into the upper chaniber through this manhole, as will be described.
Discharge means are provided in the form, in the present example, of a closable aperture or manhole 122 is provided low down at the front of the shell, adjacent the upper cross wall 46. The manhole is closed by a manually operated, guillotine type gate 124. A chute 126 is mounted adjacent the manbole 122. VJhen the aggregate and bitumen have been properly mixed and heated to the correct temperature in the upper chamber, the mix can be.discharged through the manhole and onto the chute.
The heater 52 is a two ringed gas burner fed from twin gas cylinders 128 through suitable hoses. Zn the present example, the heat output 'of the burner is of the order of 75 kVd, as already noted. The domed shape helps to prevent thermal distortion of the cross walls 46, 48. Notwithstanding the domed shape, in the absence of the lower cross wali 48, the heat from the burner would be likely to overheat the upper cross wall 46, causing it to distort. The two cross walls are located close together in order to maximise heat transfer and the presence of the lower cross wal148 helps to spread the heat and avoid hot spots in the upper cross wa1146.
A layer 130 of suitable insulating material is placed around the outside of the shell 38 to reduce heat loss. The insulating material is held in place and protected by a steel sheU 132. The hot gases from the bumer pass through the apertures 56 in the shell 32 and out through the chimneys 58 via the annular passage 40_ These gases heat the wall of the shell 32 and the heat is transferred to the mix in the upper chamber.
The vessel 16 is mounted on the frame 18 so as to be capable of tilting forward about a hinged connection 134 located at the front edge of the frame. The tilting is brought about by a hydraulic ram 136. The lower end of the ram is mounted on the fxame through a pin seated between trunnions 138 welded to the frame. The upper end of the ram is similarly mounted on the vessel through a pin seated between trunnions welded to the shell 38. The ram is actuated by the driver through suitable controls, not shown. As should be clear, the vcssel remains stationary on the frame while the aggregate and bitumen are being heated arid mixed.
A safety barrier may be monnted on the fr6nt of the vehicle, surrounding the front of the vessel 16. The barrier comprises a series of steel stanchions 144 welded to the frame 18 at their lower ends and carrying rails 146 welded to their upper ends. The barrier is intended primarily to prevent damage to the vessel in the event that the -vehicle collides with objects around a work place. One example af such an object is the back of a delivery vehicle that carries aggregate and/or raw bitumen. It would often be convenient to shovel the aggregate or bitunen directly into the vessel from the delivery vehicle and the two vehicles would be brought together for the purpose.
The vehicle is obviously provided with the controls necessary for its operation. These controls would include a temperature gauge, visible from the driver's seat, for checking the temperature of the i ix; and a regulator for controlling the flow of gas to the burner.
In use, stocks of raw bitumen and stones for aggregate are brought to a convenient place in the vicinity of wherc there are potholes in a tar-sealed road. For practical purposes, raw bitumen is solid at ambient temperature and the bituunen in the stock is broken into lumps that can pass through the manhole 120. The stones should advantageously, but not essentially, be graded according to their size and left in separate stockpiles. All this is well known to experieneed operators. The vehicle 10 illustrated in the drawings has a maximum tra.velling speed of about 12 km/h.
This would be one of the factors that would determine how far away the stockpiles can be from the furthest pot hole that must be repaired. If the travelling speed renders the working range of the vehicle unacceptably low, the vehicle 10 can be carried to the work place on the back of a truck or trailer capable of a higher speed. An alternative exarnple of an apparatus according to the invention would be a vessel similar to the vessel 16 rnounted directly on a vehicle in the form of a trailer that is towed by a second vehicle. This second vehicle could be a cornmercial.ly available truck and would usually be capable of a much higher speed than 12 km/h.
The vehicle 10 is taken to the stockpiles where, in one method of use, first the aggregate is loaded into the upper chamber 42 through the manhole 120, while the muxer 50 is rotating and the burner lit. An experi.enced operator will know the sequence in which the material should loaded. This has been discussed above.
Such an operator will also know how long mixing and heating of the aggregate should be continued. Mixing is continued until the mixed aggregate is dry and has been brought up to the correct temperature. At this stage lumps of solid bitumen, conveniently at ambient temperature, are loaded by hand through the manhole 120. When the bitumen has melted and is well mixed with the aggregate, a further small quantity of dust may be added to bring the rnix to the correct consistency for use.
It should be stressed that, instead of loading one grade of aggregate after the other, it is possible to use a premixed composition of several aggregate sizes and dust and then add the bitumen. It is also possible, instead of adding the bitumen in solid (cold) form, it can be added in preheated, liquid form.
It is an advantageous feature of the present inverition that the matnhole 120 is located 5 close to the top'of the vessel. This enables substantially all of the moisture driven off the aggregate to escape to atmosphere as efficiently and quickly as possible.
This feature is made possible by the fact that the vessel is stationary in use.
Based on these parameters, the vessel and the shaft are most suitably vertically, or at least uprightly, disposed.
The mixer 50 continues to rotate while the vehicle is driven or taken to a selected one of the potholes to be repaired. The burner remains lit to keep the mix at the correct temperature. At the work site, the driver manoeuvres the vehicle so that the chute 126 is over the selected pothole and actuates the ram 136 to tilt the vessel 16 upwards and.
forwards about the hinge 134. A second operator lifts the gate 124 to allow the required amount of hot mix to flow out of the vessel and over the chute from where it ,=t is deposited in the pothole. The driver returns the vessel to the upright positiozi and backs the vehicle away from the pothole. The hot mix in the selected pothole is worked in known manner to complete the repair.
In the present example, the i.nternal diameter of the shell 32 is 126 cm. The vertical distance between the upper cross plate 40 and the domed top 36 is 75 cm, and the distance from the bottom of the shell to the upper cross plate 40 is 30 cm.
These dimensions are taken at the centre of the shell. The volume of the upper chamber 36 is thus about 930 litres. This is su.ff-icient for a charge of about 700 litres of aggregate and bitumen. The width of the annular passage 40 is 30 mm and the distance between the shell 38 and the shell 132 is 60 mm. The wall thicknesses of the shells 32, 38 and 132 are 6, 3 and I mm respe3ctiveiy. The overall diameter of the vessel is thus about,156 cm. This is less than the maximum width of the vehicle 10. The highest point on the vehicle, with the vessel mounted in place, is at the top of the vessel and is about 203 cm above the road surface: The vehicle is thus well within the height.and width limits for vehicles to be allowed on the public roads of most countries without a special permit.
The manhole 120 for filling the vessel is about 177 cm above the ground and the manhole 122 through ~Nrhich the mix is discharged is about 73 cm above the ground.
There is no serious disadvantage in allowing any mix remaining in the mixing chamber when a job is eompleted to cool and become solid as the mix can be made fluent again simply by heating. There is no pump or pipework to be cleaned at the end of a shift and, if necessary, the mixing chamber can easily be cleared by working through the manholes.
It may be noted that the machines consiructed according to the precepts of the invention can be used to heat bitumen only or bitumen mixed with quarry dust in a certain percentage to repair, fill or seal cracks in the bitu.men.layer.of roads to prevent water from destabilizing the roadbase. The same machines can also be used to seal roofs, expansion gaps in concirete roads and slabs.
It is not intended that -xecognised mechanical equivale.nts of and/or modifications of and/or improvements to any matter described and/or illustrated herein should be excluded from the scope of.a patent granted in pursuance of any application of which this specification forms a part or that claims the priority thereof or that the scope of any such patent should be limited by such rnatter further than is necessary to distinguish inventive matter disclosed herein from the prior art.
Claims (10)
1. Apparatus comprising a vessel incorporating a mixing chamber arranged to receive aggregate and bitumen means for mounting the vessel on a vehicle, heating means arranged to heat the aggregate and bitumen, and mixing means for mixing the aggregate and bitumen to form a hot mix;
the mixing means including a rotor and driving means for driving said rotor about a rotational axis that is disposed longitudinally in the shell;
said driving means including a driven rotary member through which is formed a passage, through which passage the rotor projects;
the passage and the rotor being complementarily out-of-round so that the rotor is able to slide axially in the passage while being driven by the rotary member so that, when in use, said rotor describes a path that substantially spans the space between the rotor and the shell.
the mixing means including a rotor and driving means for driving said rotor about a rotational axis that is disposed longitudinally in the shell;
said driving means including a driven rotary member through which is formed a passage, through which passage the rotor projects;
the passage and the rotor being complementarily out-of-round so that the rotor is able to slide axially in the passage while being driven by the rotary member so that, when in use, said rotor describes a path that substantially spans the space between the rotor and the shell.
2. Apparatus according to claim 1, in which the shell is of right circular cylindrical shape and the rotational axis is coincident with the longitudinal axis of the shell.
3. Apparatus according to claim 1 or claim 2, in which the shell, in use, is mounted on the vehicle in a vertical disposition.
4. Apparatus according to any one of claims 1 to 3, in which the shell comprises a cross member on which the rotor is rotatably mounted.
5. Apparatus according to claim 4, in which the cross member is located at what, in use, is the lower end of the mixing chamber.
6. Apparatus according to claim 4 or claim 5, in which the cross member is dome shaped.
7. Apparatus according to any one of claims 4 to 6, in which the rotor comprises a rotatable shaft and the apparatus comprises a bearing arrangement that is mounted on the cross member and in which an end of the shaft rotates.
8. Apparatus according to claim 7, in which the bearing arrangement comprises an opening such that material from the mixing chamber that passes between the shaft and the bearing arrangement can pass back into the mixing chamber.
9. Apparatus according to any one of claims 1 to 8, in which the vessel is mounted so as to be stationary on the vehicle when the aggregate and bitumen are being heated and mixed.
10. Apparatus according to any one of claims 1 to 9, in which the vessel includes a second chamber located adjacent the mixing chamber, the heating means being located in the second chamber.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2005905327 | 2005-09-28 | ||
| AU2005905327A AU2005905327A0 (en) | 2005-09-28 | Method and apparatus for applying hot mix for tar sealed roads | |
| PCT/AU2006/001373 WO2007035982A1 (en) | 2005-09-28 | 2006-09-22 | Method and apparatus for applying hot mix for tar sealed roads |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2621771A1 CA2621771A1 (en) | 2007-04-05 |
| CA2621771C true CA2621771C (en) | 2014-04-15 |
Family
ID=37899275
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2621771A Active CA2621771C (en) | 2005-09-28 | 2006-09-22 | Method and apparatus for applying hot mix for tar sealed roads |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA2621771C (en) |
| NZ (1) | NZ566925A (en) |
| WO (1) | WO2007035982A1 (en) |
| ZA (1) | ZA200803002B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9732280B1 (en) * | 2015-08-14 | 2017-08-15 | Fabworks & Services, Llc | Burner kettle for asphalt paving apparatus |
| CN110130192B (en) * | 2019-05-24 | 2021-02-09 | 滁州天禾建筑工程有限公司 | Small-size asphalt paving cart device capable of achieving uniform blanking |
| US11619449B2 (en) * | 2019-10-24 | 2023-04-04 | Waterblasting, Llc | Melting kettle |
| CN113832804B (en) * | 2021-09-08 | 2023-08-04 | 林逸哲 | Road paving device in low-temperature area |
| RU208926U1 (en) * | 2021-11-08 | 2022-01-24 | Федеральное государственное бюджетное образовательное учреждение высшего образования «Волгоградский государственный технический университет» (ВолгГТУ) | Device for melting and storing viscous petroleum products |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2649815A1 (en) * | 1976-10-29 | 1978-05-03 | Linnhoff & Thesenfitz Gmbh Ind | Plastic materials cooker e.g. for casting asphalt - with outer bearing race fixed to paddle mixer shaft periphery and inner race to cover |
| DE2946658A1 (en) * | 1979-11-19 | 1981-05-27 | Linnhof & Thesenfitz GmbH Industrie u. Handel, 2000 Hamburg | Mobile concrete-mixing equipment - comprises fixed upright cylindrical vessel with stirring arms on vertical shaft extending from top |
| DE3101308C2 (en) * | 1980-12-30 | 1986-05-22 | Linnhoff & Thesenfitz Maschinenbau GmbH, 2090 Winsen | Cylindrical heating kettle |
| DE3123362A1 (en) * | 1981-06-12 | 1982-12-30 | Herfeld, Friedrich Walter, Dr., 5982 Neuenrade | MIXING DEVICE |
| FR2737899B1 (en) * | 1995-08-18 | 1997-10-31 | Soc D Pavage Et Des Asphaltes | MIXING GAUGE, ESPECIALLY FOR CAST ASPHALTS |
| US6012870A (en) * | 1998-02-23 | 2000-01-11 | H.D. Industries, Inc. | Apparatus and method for transporting heated pavement repair materials |
-
2006
- 2006-09-22 CA CA2621771A patent/CA2621771C/en active Active
- 2006-09-22 NZ NZ566925A patent/NZ566925A/en not_active IP Right Cessation
- 2006-09-22 WO PCT/AU2006/001373 patent/WO2007035982A1/en active Application Filing
-
2008
- 2008-04-08 ZA ZA200803002A patent/ZA200803002B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO2007035982A1 (en) | 2007-04-05 |
| ZA200803002B (en) | 2009-05-27 |
| CA2621771A1 (en) | 2007-04-05 |
| NZ566925A (en) | 2011-03-31 |
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| EEER | Examination request |