GB1475632A - Coring tools for hollow drill strings - Google Patents

Abstract

1475632 Boring earth &c NEW JERSEY ZINC CO 15 Jan 1975 [19 April 1974] 1790/75 Heading E1F A core barrel of the type which can be pumped down a drill string 12 and latched to the drill string when it reaches its operative position adjacent the bit includes an actuating member 78 movable between a first position (Fig. 1A) in which it holds the latch 76 in its latched condition and a second position (Fig. 2) in which it holds the latch 76 in its unlatched position, the actuating member 78 being biased towards its first position and being moved to its second position to free the core barrel by an overshot assembly 154 (Fig. 4) which is pumped down the drill string and engages the core barrel. As described the latch 76 consists of two latch arms 80, 82 pivoted on a pin 84 fixed in housing 74. The actuating member 78 consists of a hollow sleeve 136, valve block 130 and a rod 108 carrying a cam block 124 and a lug 122, the assembly being movable in the housing 74. A spring 120 urges the actuating member 78 into its first position (Fig. 1A) in which the lug 122 engages face's 104 on the latch arms 80, 82 to hold them in their latched condition and in which passages 132 in valve block 130 register with passages 138 in the housing 74 to permit the flow of drilling fluid. Depressing sleeve 136 moves the actuating member 78 to its second position (Fig. 2) in which the cam block 124 holds the latch arms 80, 82 in their unlatched position and in which the flow of drilling fluid through the valve block 130 is stopped. The sleeve 136 is depressed by pumping an overshot assembly 154 down the drill string, a block 170 on the overshot assembly 154 engaging the sleeve 136 as its fingers 164, 166 engage the fishing neck or spear point 152 on the core barrel. The core barrel and overshot assembly can then be retrieved by a wireline (not shown) or by reverse circulation of the drilling fluid.