860,555. Boring earth. LONGYEAR CO., E. J. Sept. 11, 1959 [July 18,1958; July 24,1959], No. 31048/59. Class 85. Apparatus for taking a core sample from an earth formation, the borehole being other than vertically downwards so that the sampling apparatus cannot reach the core bit by freely falling, comprises a core barrel and wire-line overshot apparatus which are both fluidly propelled to the inner end of the drill string, the former to receive the core and the latter to pull the core barrel out of the drill string. As shown in Fig. 1, and in Figs. 2, 3 joined on the lines A-A, an annular core bit 15 is arranged at the end of a drill string 10 which is rotated by a conventional chuck 17 to form a core which passes into the core-receiving barrel 80 when the core barrel assembly is in position adjacent to the bit and is locked by latch-dogs 40a, 406 engaging a circular recess 33a in a wear coupling 33 incorporated in the drill string and having hardened external lands 34. The core barrel assembly is placed in the open end of the drill string and a water swivel 20 is applied, if one is not being used. The extension 44 of a member 42 having a fishing head 43 and connected by a pin 86 to a slotted latch-release sleeve 60, bears on the ends of the dogs 40a, 40b whilst the dogs are prevented from separating by the wall of the drill string, and prevents inward motion of the latch-release sleeve 60 relatively to a valve headed part 45 which is connected by a spindle 72 to the barrel 80, a block 57 backing the latch-dogs against the valve head 50 to limit movement of the latch-dog hinge pin 55 along the slots in the latch-release sleeve 60. The core barrel assembly is propelled inwardly by fluid pressure from the pump 25, the enlarged head 84 of the sleeve 60 acting as a piston, the passage of fluid to the front of the assembly being prevented by the valve head 50 obturating the passage around the sleeve 60 at the ports 85. When the assembly approaches its final position, the head 84 reaches an enlargement in the bore in the wear coupling 33, becomes inefficient as a piston and the assembly moves slower, the head finally resting in a centralizing ring 35. The latch-dogs are now registering with the recess 33a and are moved outwards by the springs 61, the extension 44 being thus freed to move inwardly with the sleeve 60 whereby the ports 85 are moved to the inward side of the head 50, as shown in Fig. 2, so that fluid may pass around and through the assembly to the core bit. The barrel 80 is screwed on to a sleeve 68 secured to the part 45 carrying the valve head 50 by the spindle 72, resilient buffers 78, 73 being provided. A ball bearing 79 permits the barrel 80 to remain stationary whilst the drill string is rotating. The inner end of the barrel 80 is fitted with a core lifter case 83 and a core lifter 82, and rests upon a fluted spacer member 39 to permit fluid flow to the core bit 15. When the barrel 80 is full, the fishing head 43 is pulled back, as described below, by the wire line overshot apparatus, the sleeve 60 being pulled out so that the bevelled edges 67 cam the dogs 40a, 40b out of the recess 33a, the relative movement of the sleeve 60 and the head 50 bringing the former entirely away from the latter. Fluid, which would otherwise be expelled plunger-wise from the drill @tem by the retracting assembly, is able to flow through the ports 85 to the inner end of the assembly. A valve may be incorporated in the string to prevent fluid from being wasted. One form of overshot apparatus is shown in Fig. 21. Spring-closed pivoted jaws 226, 227 which are opened by and grip over the fishing head 43 are pivoted at 230 in a slot in a member 229 secured within a sleeve 237 by a pin 240. A member 241 is slidable in the sleeve 237, in which it is retained by a head 241a meeting a shoulder 237b, and is screwed to a thimble 243 to which the wire line 222 is attached. The thimble is ported at 246 to provide a fluid path to an axial passage 247 and radial ports 248 in the member 241. A resilient packing 253 is clamped on the member 241 by the thimble, and forms the piston seal when the overshot apparatus is being fluidly propelled to the inner end of the drill string. During this inward motion, the backing washer 254 of the packing 253 abuts on the sleeve 237 and the ports 248 are obturated by the wall of the sleeve so that there is no fluid passage through the apparatus. When the jaws 226, 227 have gripped the head 43, a pull on the wire 222 brings the head 241a against the shoulder 237b, the packing 253, 254 being withdrawn from the sleeve 237 and the ports 248 being positioned between the sleeve 237 and the packing 253, so that a free fluid flow from the space around the thimble to the space around the sleeve 237 occurs during the pulling out of the overshot apparatus. If the jaws fail to grip the head 43, the overshot apparatus may be pulled back to some extent and again propelled with a hammering action against the head. The core barrel assembly of Figs. 2, 3 may be modified by transferring the valve head 50 from the member 45 to the extension 44 so that during the inward fluid propulsion of the assembly, the valve head is held by the closed dogs in position to close ports in the sleeve 60, which ports are opened by the inward movement of the extension 44 permitted by the dogs opening into latching position, the fluid then being free to pass within the sleeve 60 and to the annular space around the sleeve 60 beyond the dogs. The fluid then passes through radial passages to an axial passage in a carrier member for the core-receiving barrel, the axial passage being provided with a spring-pressed ball valve which lifts during the withdrawal of the assembly to permit free flow of fluid through the whole assembly. The carrier member is flanged to land upon a ledge in a landing nipple, so that the barrel 80 is spaced slightly from the core bit. The barrel 80 is resiliently mounted whereby, when it is full or the core jams, it yields outwardly. In another modification, Fig. 14, the latch-dogs 195, 196 when in closed, i.e., unlatched position, present, with the latch-release tube 192 and the latch body 191 to which they are hinged, a substantially closed circular crosssection, so that this composite section of the dogs' body 191 and the slotted tube 192, acts as a piston for the fluid inward propulsion of the assembly. The fluid pressure passes through a longitudinal channel 201 cut in the plug 193 carrying the fishing head 194 to a space 194a above the body 191 which has diametrically opposed channels 202 leading one to the side face of one dog and the other to the side face of the other dog. The dogs have ports 204, 205 which, when the dogs are unlatched, are out of register so that there is no free path for fluid from the channels 202 to the annular space 202 beyond the dogs. When the dogs open into latched position, the ports 204, 205 register and the fluid passes freely to the core bit. In a modification of the overshot apparatus shown in Fig 21, the wire 222 is not connected directly to a thimble 243, but is connected to a member having limited sliding motion within an open ended sleeve replacing the thimble. The said member carries a head which fits and acts pistonwise within the drill string 10. The piston head has circularly spaced longitudinal ports which are sealed by the piston bearing against the end of the sleeve when the overshot apparatus is being fluidly propelled into the string. When the overshot apparatus is pulled back, the piston head lifts from the sleeve end and a free path for fluid through the apparatus is provided. In another modification, the spring-pressed jaws 326, 327, Fig. 28, are shaped to form with the slotted member 329 to which they are pivoted by a pin 330, a substantially closed circular section which acts as the piston for fluid propulsion in the drill string. With this modification an overshot assembly release member may be fluid propelled into action, in case the overshot release assembly and the attached core barrel assembly become stuck during withdrawal, and it is desired to release the jaws 326, 327 from the fishing head. The release member comprises a cylindrical body with a closed end and an open chamfered end which latter is propelled inwardly over the body of the overshot assembly to engage chamfers on the jaws 326, 327 which are thereby released from the core barrel assembly which is left temporarily in the drill string. The cylindrical body has a winding slot to enable it to be placed around the wire. Specifications 752,869 and 816,271 are referred to.