GB904373A - Improvements in and relating to earth-drilling equipment - Google Patents

Abstract

904,373. Boring earth. ECONOMIC FOUNDATIONS Ltd. Feb. 24, 1960 [June 17, 1959], No. 20885/59. Class 85. Feed pressure is applied to a kelly bar by a member which rotates with the kelly and has at least two members operable to grip or release kelly on opposite sides thereof, means being provided to apply downward thrust to the rotating member and thus to the kelly. In Fig. 4, a plate 17 having a square central hole to fit the kelly 18 is secured to a lower circular plate 21 having a spacing flange 22 which forms an annular recess for slippers 15 which support the plates 17, 21 from a stationary ring 14. The ring is carried by hydraulic rams 12 which raise the plates on the kelly and then reverse to pull the kelly down. The thrust is transferred from the plate 17 to the kelly by toggles 24 comprising plates which are accommodated in recesses between the plates 17, 21 or in inserts 25 in those recesses. The toggles 24 are shaped to embrace the square kelly and have lateral extensions which are engaged at diametrically opposed points by two means, each comprising spaced abutments 33, 34 on a rod 30 slidable in the plate 17 and having a spring 32 adjustable by a nut 31. The springs tend to keep the edges 27 of the toggles in operation against the kelly. When the plates 17, 21 are raised by the rams 12, heads on the rods 30 strike a stationary framework 36, the abutments 33, 34 being depressed to disengage the toggles 24 from the kelly. When the rams 12 again descend, the heads are released and the springs 32 bring the toggles into action.