Excavating – Ditcher
Reexamination Certificate
2001-11-13
2003-12-09
Novosad, Christopher J. (Department: 3671)
Excavating
Ditcher
C037S348000, C037S352000, C037S355000, C037S357000
Reexamination Certificate
active
06658767
ABSTRACT:
The present invention relates to a method of trenching, and to a trenching apparatus, both of which are applicable in particular, but not exclusively, for cutting a trench in rock.
There are known many trenching machines for digging trenches in soil by use of a prime mover such as a crawler tractor, or a conventional tractor pulling a trailer, in which a cutting device is positioned in the trench on a boom. The main examples are a cutting rotor rotating about an axis transverse to the trench, known as a ripper cutter, or one or more cutting rotors rotating about an axis aligned along the length of the boom, generally known as a milling cutter, or a cutting device having an elongate endless support means carrying a plurality of cutting elements and trained along upper and lower runs on the boom, known as a chain cutter. Where a cutting rotor is used this is mounted on the distal end of a boom projecting forwardly and downwardly from the prime mover, relative to the direction of digging of the trench Where a chain cutter is used, this is normally mounted on a boom extending downwardly and rearwardly from the prime mover relative to the direction of cutting of the trench. In such an arrangement the elongate support member moves in a direction such that the cutting elements move downwardly around the distal end of the boom and upwardly and forwardly along the lower run of the moving elongate support member. There is normally provided in all these forms of trenching machines, a positioning device for raising and lowering the distal end of the cutting boom to vary the height of the trench. Examples of such trenching machines are found in, for example, CH-A-239495 (Entreprise de Grands Travaux SA), and WO 95/13433 (Mastenbroek & Company Limited).
All these forms of trenching machine are generally satisfactory for trench cutting in normal soil conditions, but are not suitable fur cutting trenches in rock or other hard ground materials. For cutting trenches in hard rock, labour intensive methods are generally adopted using percussion tools and explosives.
In another art unconnected with trenching, tunnelling machines for tunnelling into rock are known in which a cutting rotor known as a ball cutter protrudes forwardly on a boom from a prime mover, and is movable in a vertical plane by pivoting of the boom on the prime mover. In use the cutting rotor is lowered to the floor of the tunnel and the prime mover advances with the cutting rotor to engage the end face of the tunnel at floor level, to produce an undercut. The cutting boom is then pivoted in an upward direction by hydraulic rams so that the cutting rotor or rotors are lifted upwardly to cut a slice of material from the end face of the tunnel. The cutting boom is raised by application of a force between the cutting boom and the floor of the tunnel. In a variation of such a device, there is provided a form of chain cutter trained along upper and lower runs along the cutting boom and around the distal end of the cutting boom, for use for example in mining coal or soft stone. In such a machine the endless moving support means carrying the cutters is driven in a direction such that the cutters move upwardly around the distal end of the boom and move rearwardly along the upper run of the moving support member. Examples of both forms of tunnelling equipment are found in leaflets published in 1982 by Hawker Sidley Dosco Overseas Engineering Limited and entitled DOSCO 1982 “The Twin Boom TB600” and DOSCO 1982 “Mark II Heavy Duty Dintheader”.
In addition to this prior art, there is disclosed in EA-A-008082 (Wallace) a machine for cutting a trench in rock by use of a ripper cutter. EP-A-0080802 also acknowledges as prior art a known trench cutting machine comprises a giant chain saw mounted on a crawler chassis and equipped with tungsten carbide teeth which literally saw away the rock. However, this machine suffers from the disadvantage that considerable bounce is generated along the saw, especially when cutting the harder rooks, and this reduces the cutting efficiency. Primarily the problem arises because of the long unsupported length of the cutting arm. There is also discussion in EP-A-0080802 of ball cutting machines such as have been described above in tunnelling, and it is said that other rock cutting machines are known for face mining operations and these comprise a rotatable cutting head carried at the end of a boom pivotably attached to a crawler chassis. However, it is said that these known machines cannot be used for cutting trenches and furthermore suffer from a similar vibration problem because they too have a long unsupported boom carrying the cutting head.
In EP-A-0080802 it is said that these difficulties are overcome by providing a machine for cutting a trench in rock having a pivoted boom with a rotatable cutting head at the distal end and a telescopic control arm extending between a mobile work platform and the end of the boom adjacent the cutting head, the telescopic control arm being an hydraulically operable ram serving to move the cutting head on an arcuate path about the pivot axis of the boom. The machine operates by the hydraulic ram applying to the cutting head a force having a major vertical component. In operation the machine is positioned to straddle the line of the trench and the boom is lowered into contact with the ground. The cutting head is rotated whilst applying force by way of the hydraulic ram to move the cutting head on an arcuate path downwardly and to remove rock from the forward end of the trench. A conveyor is positioned on the floor of the trench and the spoil is carried away. The boom is then raised and the machine moved forward and the process is repeated.
It is said that the problem of vibration and bounce with the relatively long boom is avoided because the position at which the ram is coupled to the boom adjacent to the cutting head adds to the stability of the cutting head so eliminating the vibration and bounce problems which would be expected if the ram were omitted and the cutting force was applied by the long boom. It is said that because the control arm applies the necessary loading of the cutting head, and because of the relatively short distance between the cutting head and the point of support, the problem with cutter head bounce is largely avoided.
However a disadvantage arises with this form of machine, as is acknowledged in EP-A-0080802, in that the force applied at the cutting head tends to lift the machine out of contact with the ground. It is suggested that additional ballast may carried, but it is nevertheless inescapable that there is a limit to the amount of force which can be applied to move the cutting head on its arcuate path, without the surface mounted components of the apparatus lifting from the ground surface.
It is one object of the present invention to provide a trench cutting apparatus in which the problems outlined above are avoided or reduced.
In accordance with the present invention there is provided a method of trenching comprising positioning in a trench a cutting device mounted on a prime mover movable on the ground surface above the trench; engaging an end face of the trench with the cutting device; and moving the cutting device in a vertical plane while operating the cutting device, so as to cut material from the end face of the trench; in which the method includes positioning the cutting device against the end face of the trench below the level of the ground surface, and moving the cutting device forward in the trench while operating the cutting device, so as to produce an undercut in the end face of the trench; and lifting the cutting device upwardly from the undercut by exerting A force between the cutting device and the ground surface above the trench and operating the cutting device during the upward movement so as to cut material from the end face of the trench.
It is to be appreciated that where features of the invention are set out herein with regard to a method according to the invention, such features may also be provided with regard to apparat
Geelhoed Jack
Kelly Keith R.
Mastenbroek Ltd.
Novosad Christopher J.
Pillsbury & Winthrop LLP
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