GB1477069A - Drilling tools for drilling holes in the ground - Google Patents

Abstract

1477069 Boring earth &c INSTITUT FRANCAIS DU PETROLE 27 June 1975 [11 July 1974] 27332/75 Heading E1F In a drilling tool, a rotatable body 1, connected to a tool-holder or drill pipe 9, carries rotary cutters 5, (6), 7, such as shown on the ends of arms 2, (3), 4, each cutter having e.g. rings of teeth, and flushing means are provided e.g. ducts 14, (16) so that flushing fluid jets out substantially in the direction of advance of the tool and at the level of the cutters 5-7. A skirt 19 extends from the body 1, e.g. between arms (3), 4, the skirt having a diameter slightly less than that of the drilled hole and delimiting a space above the cutters 5-7. In use this space becomes filled with fluid which has irrigated the cutters and the working surface, the fluid being discharged through a passage 19a, and suction means being provided so that the fluid is moved in a direction opposite that of the advance of the tool. In the embodiment shown the flushing fluid is provided through a passage 10 which connects with the ducts 14, (16), these opening between the cutters at 14a, (16a) and through lateral apertures (17) located to wash the cutters directly. Plates 18, 20 prevent any direct communication between the space around the cutters and the annular space 21 outside the upper part of the body 1. A further duct 15, also connected to the passage 10, opens in the passage 19a in a direction opposite the direction of advance of the tool, fluid issuing from the outlet 15a providing the required suction. The minimum cross-sectional area of the passage 19a at S and the size of the apertures 14a-16a are so chosen that the flow rate of fluid passing into the annular space 21 is at the most equal to the flow rate of irrigating fluid supplied by ducts 14, (16). The passage 19a may be extended upwardly by a convergent-divergent nozzle secured to the drill pipe 9, this providing additional suction.