Trench cutting apparatus and method

Abstract

A trench cutting apparatus comprises a main body portion, ground contacting conveying means on which the body portion is mounted and by which the apparatus can traverse the ground and at least one soil cutting device operable to cut a trench wherein the attitude of the soil cutting device is adjustable between a first use configuration configured for cutting a linear trench portion and a second use position configured for cutting a curved trench portion, said second use position being selected to minimise undercutting of a trench wall as said curved trench portion is formed.

1 . A trench cutting apparatus comprising a main body portion, ground contacting conveying means on which the body portion is mounted and by which the apparatus can traverse the ground and at least one soil cutting device operable to cut a trench wherein the attitude of the soil cutting device is adjustable between a first use configuration configured for cutting a linear trench portion and a second use position configured for cutting a curved trench portion, said second use position being selected to minimise undercutting of a trench wall as said curved trench portion is formed. 
     
     
         2 . Apparatus as claimed in  claim 1  wherein the soil cutting device is a chain cutter or a jetting cutter. 
     
     
         3  Apparatus as claimed in  claim 2  further comprising a control device wherein the attitude of the soil cutting device is adjustable under the control of the control device. 
     
     
         4 . Apparatus as claimed in  claim 3  wherein the attitude of the soil cutting device is automatically adjusted by the control device in dependence on the radius of curvature required for the trench being formed. 
     
     
         5 . Apparatus as claimed in  claim 2  wherein the soil cutting device is a chain cutter comprising a plurality of soil cutting teeth mounted for movement in an endless loop, the chain cutter having, in an operational position, a lower end at which the soil cutting teeth cut the soil to form the trench and a upper end at which the teeth are spaced apart from the soil, said lower end having an outer edge and an inner edge which respectively define opposed boundaries of the trench being cut, and wherein the adjustment in the attitude of the chain cutter is such that at least a portion of said outer edge is displaced towards the direction of curvature of the trench. 
     
     
         6 . Apparatus as claimed in  claim 5  wherein the attitude of the chain cutter is adjusted by rotating the chain cutter about a nominally horizontal axis. 
     
     
         7 . Apparatus as claimed in  claim 2  wherein the soil cutting device is a jetting cutter having, in an operational position, a first portion from which cutting fluid is expelled along a line of action to cut the soil to form the trench and a second portion which is in fluid communication with a supply of cutting fluid and wherein the adjustment in the attitude of the jetting cutter is such that said line of action of the cutting fluid is displaced towards the direction of curvature of the trench. 
     
     
         8 . Apparatus as claimed in  claim 7  wherein the attitude of the jetting cutter is adjusted by rotating the jetting cutter about a nominally horizontal axis. 
     
     
         9 . Apparatus as claimed in  claim 6  further comprising actuators coupled to the soil cutting device and configured to adjust the attitude of the soil cutting device by rotating the soil cutting device about said horizontal axis. 
     
     
         10 . Apparatus as claimed in  claim 5  wherein the change in attitude of the soil cutting device is effected by a change in attitude of the body portion, the attitude of the soil cutting device being maintained in fixed relation to the body portion. 
     
     
         11 . Apparatus as claimed in  claim 10  wherein the attitude of the body portion is adjustable by adjustment of the spacing of one or both of the ground contacting conveying means with respect to the body portion. 
     
     
         12 . A method of cutting a trench comprising providing a trench cutting apparatus having an soil cutting device which is adjustable between first and second attitudes and prior to cutting a curved portion of the trench, adjusting the attitude of the soil cutting device to an attitude in which undercutting of the trench wall of said curved portion is minimised. 
     
     
         13 . A method as claimed in  claim 12  wherein the attitude of the soil cutting device is adjusted in dependence on the radius of curvature of the trench being formed 
     
     
         14 . A method as claimed in  claim 12  wherein the adjustment in the attitude of the soil cutting device comprises rotating the soil cutting device about a nominally horizontal axis. 
     
     
         15 . A method as claimed in  claim 12  wherein the trench cutting apparatus comprises a main body portion to which the soil cutting device is attached and the adjustment in the attitude of the soil cutting device comprises adjusting the attitude of the main body portion. 
     
     
         16 . A method as claimed in  claim 12  wherein the trench cutting apparatus is an apparatus as claimed in  claim 1 .