Joint cutter This invention relates to a joint cutter, and to a vchicle
having a joint cutter, for cuffing joints in hydraulically bound materials, for example concrete.
Hydraulically bound materials (HBM), for example concrete, have a tendency to crack when they dry due to shrinkage caused by a reduction in the volume taken up by water when the water evaporates. It is preferable to control the manner in which the concrete cracks, rather than allow uneonliolled cracking, as this could result in weaknesses in the concrete in highly stressed areas (fOr example the areas of concrete underneath vehicles' tyres iii a busy road), and increased likelihood ol' damage to the concrete in extreme weather conditions (for example freeze-thaw frost shattering due to rain water accumulating in cracks in the concrete and expanding when the temperature goes below freezing point). The Specification for highway Works (Volume 1, November 2004), clause 818, defines requirements for Induced Cracking of hIBM: (I) Where the IIBM layer in the pavement construction comprises IIBM with a strength class equal to or exceeding C 8/10, C 9/12 or 13 that layer shall have cracks induced during construction, as described below, at a maximum longitudinal spacing of 3 iii 10%. Where any underlying pavement construction comprises cracked HBM the cracks in the overlying HBM shall align with cracks in the underlying construction.
(2) Cracks shall he induced in Fresh material. The transverse cracks shall be induced by grooving the fresh material to a depth which leaves a vertical groove not more than mm wide, between one half and two thirds the layer thickness alter compaction, over the thll width of the pavement. A dc-bonding material 1...] shaH be inserted into the groove prior to final compaction, extending from the bottom of the groove to not less than half the height of the groove. During linal compaction oF the material, the groove shall he closed at the surface and the dc-bonding material shall be Fully encased and remain continuous within the closed groove.
Current practice is to produce the joint either by a hand shovel and apply a de-bonding agent from a watering can or similar, or to operate a whacker plate with a metal fin attached to the underside (de bonding agent applied in a similar manner). However, these methods have a number ol'disadvantages: Inconsistent joint width
Inconsistent introduction of the de-bonding agent
Carried out by a person on Wot -only allows small areas to be covered at a time Requires manual handling and repeated actions by operatives Potential health and safety issues relating to hand-arm vibration (HAV) The last two points are of key concern as part of the continual improvement in health and safety. Such a factor may be important at pre-tender stage for major contracts. It would be advantageous to provide an apparatus and method for inducing cracks in hydraulically bound materials which overcome the above disadvantages, suitable fin applications according to clause 818 above and other applications.
According to an aspect of the invention there is provided a joint cutter for cutting ajoint in a hydraulically bound material, the apparatus configured to be attachable to a vehicle, said apparatus comprising cutting means configured to have two configurations, a first configuration in which the cuttin.g means is lowered to, in operation, cut the said joint in the said hydraulically bound material, and a second configuration in which the cutter is raised, and applying means for applying a dc-bonding agent to the said joint.
Preferably the hydraulically bound material comprises concrete, for example paver laid concrete or roller compacted concrete. Typically the vehicle to which the apparatus may be attached comprises a road roller, for example a small tandem roller. Preferably Il-ic cutting means comprises a hardened steel disc or wheel. Other materials and shapes may also be used. The cutting means may be rotatably mounted on the joint cutter, or it may he fixed. The width of the disc may preferably he in the range 10 to 25 millimetres, more preferably 15 to 20 mm. [he diameter of the disc may preferably be in the range to 1000 mm, more preferably 400 mm or 540 nun.
Preferably the applying means includes a nozzle for spraying the dc-bonding agent into the joint. Preferably the cutting means is provided on an arm, hydraulically actuated to provide the first and second configurations. Preferably the arm is pivotally mounted on a support imit of the joint cutter. Alternatively the arm may be mounted directly on the vehicle. Preferably the applying means includes a pump or sprayer. Preferably the dc-bonding agent comprises a bituminous tack coat, br example a bitumen emulsion.
Optionally a crack-inducing agent may he used.
In another aspect there is provided a joint cutting vehicle comprising a joint cutter according to the invention mounted to a vehicle.
According to a further aspect of the invention, there is provided a method of cutting a joint in a hydraulically bound material using a joint cutting vehicle according to the present invention, the method comprising lowering the cutting means of the joint cutter of the vehicle to engage it with the hydraulically bound material, moving the vehicle in order to cut the hydraulically bound material with the cutting means, and applying a de-bonding agent to the joint thus formed.
We describe a joint cutter used to provide ajoint in paver laid concrete (also known as Roller Compacted Concrete) and hydraulically Bound Materials (HBM). This joint is then filled with a dc-bonding agent (typically, but not exclusively, bituminous tack coat). The material is then roller compacted to form a visibly continuous material which will crack in a controlled manner along these induced planes of weakness during shrinkage.
In particular. the joint cutter has the benefits of: Consistent joint width
Consistent introduction of the dc-bonding agent
Mounted on a mobile device (small tandem roller) -enables large areas to he covered Elimination of manual handling/repeated actions by operatives Elimination of potential health and safety issues relating to hand-aim vibration Features of the above described aspects and embodiments of the invention may be combined in any peimutation.
Embodiments of these and other aspects of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a side view of ajoint cutler mounted on a vehicle, according to the present invention.
Figure 2 shows a front view ofajoint cutter mounted on a vehicle, according to the present invention.
Figure 3 shows a plan view of a joint cutter mounted on a vehicle, according to the present invention.
Figure 4 shows a perspective view of a joint cutter according to the present invention.
Figure 5 shows a front view of ajoint cutter according to the present invention.
Figure 6 shows a side view of a joint cutter according to the present invention.
Figure 1 shows a side view of thejoint cutter, mounted on a vehicle (in out]ine), in this case a road roller. A hardened steel cutting wheel (I), diameter 540 millimetres, is mounted on an arm, pivotally mounted on a support by means of a bearing (2). i'he support may form part of the joint cutter, or alternatively it may he on the vehicle.
Between the cutting wheel and the bearing is provided another pivot (3), here used to mount a hydraulic ram (4) between the support and the arm. A rain down pipe (5) and a ram up pipe (6) are provided to supply hydraulic fluid to the ram to actuate the ram. A hydraulic 2-way directional control valve (7) may he used to control the actuation ol the ram, and provide an up-down control over the position of the cutting wheel. A hydraulic pressure line (17) is provided to supply hydraulic fluid under pressure from the vibrator motor. A return hydraulic pipe (8) is provided to the hydraulic tank; the tank may be provided as part of' the joint cutter, or the joint cutter may use a hydraulic tank from the hydraulic system of the vehicle, if one is available.
A nozzle (9), diameter 10 millimetres, is mounted near the cutting wheel, preferably behind the wheel in the normal direction of travel in operation, for clean injection of tack coat into the joint. The nozzle is connected to a. dc-bonding agent application pipe (10). !iiis carries de-bonding agent (I 1) from a pump.
A tap (12) is provided to control the flow of dc-bonding agent in the joint cutter. This allows dc-bonding agent, preferably a bituminous tack coat, to be applied to the joint when ajoint is being cut, and for the amount ol'agent applied to be controlled, and to stop the flow of agent when the joint cutter is not cutting a joint. An existing on-board water tank (13) of the vehicle may be used to supply the dc-bonding agent, or a] teniati vel y the joint cutter may include a separate tank. A suction pipe (14) is provided to the supply side oI'the pump from the tank. The pump, here used to supply agent under pressure to the nozzle to spray agent onto the joint, may be supported by a support welded to the existing framework (15) of the vehicle. A folded steel cover (16) may be provided for the de-bonding agent sprayer.
Figure 2 shows a front view olthc joint cutter mounted on the vehicle (in outline). This shows the support unit welded to the existing chassis at the point (21). A folded sheet steel bracket (22) may he bolted to the existing bodywork to hold the 2 way directional control valve and dc-bonding agent spray tap. It will be apparent to the skilled person that other attachment methods than welding and bolting are also suitable. Depending on the materials used, brazing or adhesive bonding may also be used.
Figure 3 shows a plan view of the joint cutter mounted on the vehicle (in outline). The nozzle may beheld by a grub screw with a handle (31), which facilitates adjustment of the nozzle. the dc-bonding agent sprayer (33) is shown from above. An example of the vehicle, in this case a road roller, is the Bornag 80 ADII 2, available from BOMAG (Great Britain). Ltd. of Aylesford, Kent. Other road rollers and other vehicles will also he suitable for mounting the joint cutter.
Figures 4. 5 and 6 show a visual layout of the cutter without the roller present, showing the spray injector for thermal shrinkage cutting. Figurc 4 shows a perspective view. The red pipes show the flow of dc-bonding agent. The blue pipes show the flow olthe hydraulic fluid. Figure 5 shows a front vicw. Figure 6 shows a side view.
No doubt many other elièctive alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of' the claims appended hereto.