US2747841A - Core-lifting means for rotary drills - Google Patents

Description

May 29, 1956 w. M. ADAMsoN ET AL. 2,747,841

CORE-'LIFTING MEANS FOR ROTARY DRILL-S May 29, 1956 w. M. ADAMsoN ETAL CORE-LIFTING MEANS FOR ROTARY DRILLS 2 Sheets-Sheet Filed Aug. 15, 1952 2 211@ U ,ab V/ /I/V/ I I N x l C I I 7 2 N I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I m2, M7 2@ ma o A W. O M13. E. F w w 1 Ilm Jr T 0 a 7\2&0/12054/57,6 5 4 4 111222522222 United States Patent() CORE-LIFTING MEANS FR ROTARY DRILLS William Murdoch Adamson, Germiston, Transvaal, and George Bernard Weldon, Johannesburg, Transvaal, Union of South Africa Application August 1S, 1952, Serial No. SdhdZ Claims priority, application Union of South Africa September 8, 1951 5 Claims. (Cl. Z55-72) This invention relates to rotary drills and in particular, to core-lifting means for such drills.

As it is the object of drilling generally to sample subsurface strata, it is of the greatest importance to recover intact the core which rises within the core barrel to ensure proper analysis.

Various proposals have been made to this end. rhus in an earlier proposal, which is still widely used, the drill bit is tapered inwardly and provided with an internal core lifter adapted to tit snugly around the core and to be jammed into the taper when the core barrel is pulled up, thus gripping the core tightly and breaking it off.

This type of core lifter has two main disadvantages. In the irst place, it often happens that relative movement takes place between the core and the vcore lifter resulting in damage to the core, or that the core is not broken oi as near the bottom as is desired. Secondly even if no relative movement should take place, a small part of the core will still be lost since the barrel will in any event have to be moved a short distance relative to the core in order to effect jamming of the core-lifter in the taper. Because of these disadvantages, it has always been found necessary to drill a few inches deeper than actually required in order to compensate for the lost piece of core.

Attempts have been made positively to engage the core lifter with the core before lifting is commenced. rihus, for example, it has been proposed to provide a mechanism in the core barrel which can be operated by liuid pressure positively to jam the core-lifter into the taper of the bit before lifting is commenced.

These proposals have solved the problem of complete core recovery to a great extent but still suffer from the disadvantage that, although the core-lifter is positively engaged with the core when it is desired to withdraw the core, no positive means is provided for releasing the core-lit`ter from its initial position in the taper of the bit prior to commencing drilling operations. A further disadvantage is that the mechanism employed is normally of a fairly complicated nature.

The object of the presen-t invention is to provide corelifting means of the type in which the core lifter is positively engaged with the core before lifting is commenced, which will overcome or minimize the disadvantages mentioned in the f regoing and which will be simple in construction and easy to operate.

According to the invention, we provide, in a rotary drill in which fluid is passed tothe dril1 bit under pressure, core-lifting means comprising in combination, fluid pressure operated means operatively connected to the core lifter and adapted, upon uid pressure being applied -to it, to retract the core-lifter from its position in which it will normally tightly grip the core, and spring means adapted to move said core-lifter into a position in which it will tightly grip the core upon said fluid pressure being released or atleast `substantially reduced.

More Vspecifically in a rotary drill in which uid `is passed to the drill bit under pressure, the core-lifting means comprises, in combination, a cylinder and piston 2,747,841 Patented May 29, 1956 ICC therefor, one of which is xed and the other movable relative thereto; means for operatively connecting the movable piston or movable cylinder to the core-lifter; port means allowing fluid under pressure to enter said cylinder on the one side of said piston so as to cause the movable piston or movable cylinder to move the core-lifter from its position in which it will normally tightly grip the core; and spring means arranged to act against the aforesaid movement of the piston or cylinder and to move the core-lifter into a position in which it will ltightly grip the core when fluid pressure to said cylinder is released or at least substantially reduced.

The movable piston or cylinder may be operatively connected to the core-lifter by means of a tube which is a loose lit within the normal core barrel and lis large enough to accommodate the core to be lifted.

A swivel-head may be provided between the said tube and the movable piston or cylinder.

In a preferred embodiment of the invention the piston is iixed and the cylinder is movable relative to the piston. ln one arrangement the piston is supported on a hollow stem secured to the core barrel or similar part and fluid under pressure enters the cylinder through such stein.

in carrying out the invention, the core-lifting means is wholly accommodated within the core barrel and the tube connecting the movable piston or cylinder and the core-lifter, is of suicient length to accommodate the length of core which it is desired to remove. The operating mechanism is thus located above the upper extremity of the core.

The fluid flowing under pressure through the drill rods and core barrel to the drill bit lis utilized to operate the core-lifting means and the ow may be intercepted either partially or completely for this purpose. It is to be understood, however, that, in the latter case, .outlet ports must also be provided in the iiuid pressure operated means in addition to the inlet ports already referred to.

if desired, the lluid pressure operated means may also be provided with a relief valve to allow surplus fluid remaining in the drill rods and core barrel above such means, to escape, once the pressure has been released.

A preferred embodiment of the invention will now be described, by way or example only, with reference to the accompanying drawings in which Figures l and 2 are cross-sectional views taken on a plane longitudinally through a core-barrel and drill bit and core-lifting means, and respectively showing the parts in their extreme operating positions.

Referring to the drawings, the drill bit a, is in known manner, secured to the .core barrel b by means of a reaming shell c and the opposite end of the core barrel b is provided with a head d for securing it to the drill rods (not shown) also Vin known manner.

The core-barrel b is of suicient length to accommodate the desired length of core and also the core-lifting means presently to be described.

The core-lifting means comprises a tube l which its loosely within the core-barrel b and has an inner diameter large enough to receive the core without gripping it. The forward end 2 of the tube 1 lits snugly into a socket 3 formed on the rear end t of the core gripper S. y

The core gripper 5 comprises a tubular steel member provided with symmetrically disposed longitudinal slots 6 extending from the forward end i of the member to a point near the rear end si. Thenormal inner diameter of the core gripper 5 is such as to loosely accommodate the core (not shown) but, by virtue of the slots 6, the diameter can be reduced so .as to grip the core by forcing the forward end 7 into the tapered inner periphery 9 of the drill bit a. Y

The core-lifting means further comprises a movable cylinder 10 and a fixed piston 11 therefor. The piston 11 is carried on the forward end 12 of a hollow stem 13 the rear end 14 of which is screwed into a screw-threaded socket 15 provided in the core-barrel head d co-axially therewith. The forward end 12 of the stem 13 is of smaller external diameter than the remainder and a shoulder 16 is formed on the stem as a result of the difference in diameters.

The piston 11 comprises a flanged collar 17, the one flange 1S being adapted to abut against the shoulder 16 and the other flange 19 having an external diameter slightly less than the internal diameter of tbc cylinder a cup leather 20 between the flange 1S and a retaining washer 21; a distance piece 22 in the form of a ring surrounding the lower end of the stem 13 and a second cup leather 23 between said distance piece 22 and a further retaining washer 24. The component parts of the piston referred to above are all compressed together as a unit against the shoulder 16 by means of a nur 25' screwed onto the screw-threaded extremity 26 of the forward end 12 of the stem 13. A further locking nut 27 is also provided.

The distance piece 22 is provided with au internal peripheral recess 28 to form an annular chamber 29 between it and the forward end 12 of the stem 13. Outlet ports 30 are disposed in the wall of the distance piece between the chamber 29 and an annular chamber 31 bounded by the cylinder 10, distance piece 22, retaining washer 21 and cup leather 23.

The hollow stem 13 provides a fluid passage 32 which converges into a smaller passage 33 in the forward end 12 of the stem 13. Relief ports 34 connecting the passage 33 and the chamber 29 are provided in the wall of the forward end 12 of the stem 13. An adjustable needle 35 which is screwed into the forward end 12 of the stem 13, is adapted to co-act with the relief ports 34 and to provide an adjustment therefor.

The cylinder 10 is internally screw-threaded at the rear end 36 thereof to receive a screw-threaded ring plug 37 which is a sliding iit on the stem 13. The cylinder 1G is furthermore provided internally with a peripheral step 38, and a resilient lluid seal 39 is housed in a peripheral recess 40 formed between the one side 38a of the step 38 and the plug 37. The opposite side 3812 of the step 38 forms an abutment for the flange 19 of the collar 17.

An annular chamber 41 is formed between the wall of the cylinder 10, the stem 13, collar 17 and uid seal 39. The chamber 41 is in communication with the passage 32 by means of inlet ports 42 which have a substantially larger area than the ports 34.

Exhaust ports 43 are provided in the wall of the cylinder 10 in such a position that, when the collar 17 abuts against the step 38, they are in line with the chamber 31. These exhaust ports 43 have a substantially smaller area than the inlet ports 42.

' The skirt 44 of the cylinder 10 is internally screwthreaded to receive the externally screw-threaded end 4S of a tubular extension 46 within which is housed a compression spring 47 adapted to be compressed between the piston 11 and a spring adjusting plug 43 screwed into the internally screw threaded end 49 of the extension 46.

The end 49 of the extension 46 is connected to the outer member 50 of an anti-friction bearing swivel-head 51 and the pin member 52 of the swivel head is screwed into and securely held in a plug 53 which is adapted to t snugly into the rear end 54 of the tube 1.

It will be appreciated that the cylinder 19, extension 46, swivel head 51 and tube 1 are all a loose tit in the core-barrel b so as to provide an annular passage between these members and the core-barrel for the fluid flowing under pressure to the drill bit a.

In operation, with the core lifting means in normal position, as shown in Figure l, water is pumped down the drill rods in the usual manner and it is led into the passages 32 and 33 from whence it escapes through the inlet ports 42 and, as will be clear from what follows,

also momentarily through the ports 43 via the ports 34, chamber 29, ports 30 and chamber 31.

By virtue of the fact that the ports 42 are larger in area than the ports 34, the water escaping through the former will immediately create a pressure in the chamber 41 which will cause the cylinder 10 to move rearwardly towards the core-barrel head d, as shown in Figure 2, against the action of the spring 47 the compression of which has been pre-set, by adjustment of the plug 48, to be overcome by the pressure of the water in the cylinder.

The movement of the cylinder, as aforesaid, results in a change of the position of the ports 43 with respect to the piston 11 and they are brought into communication with the chamber 41. There now being no outlet from the chamber 31, flow of water through the ports 34 ceases. However, since the ports 43 are now in communication with the chamber 41, water from this chamber will flow through these ports into the passage between the core-barrel b and the cylinder 10 and thence to the drill bit a thus completing the normal flow.

By reason of the fact that, the ports 42 are larger in area than the ports 43, pressure in the chamber 41 will be maintained and as result the cylinder 10 will also be maintained in the position to which it was initially moved against the action of the spring 47.

The cylinder 10 being operatively connected to the core gripper 5 through the extension 46, swivel-head 51 and tube 1, will naturally impart corresponding movement to the core gripper S. Thus, when the cylinder is moved by the water pressure as aforesaid, the core gripper 5 will be retracted from the tapered inner periphery 9 of thc drill bit a and assume its normal inner diameter which, as already stated, is slightly larger than the diameter of the core.

When drilling operations are now commenced, the core gripper and inner tube 1 will pass freely over the core.

When it is desired to lift the core, drilling is stopped and the water supply is closed off. In the result, pressure in the cylinder 10 is immediately released and the compression spring 47 thrusts the cylinder downwards and with it also the core gripper. The core gripper thus becomes jammed in between the core and the tapered inner periphery 9 of the bit a and securely grips the core at that point. Removal of the core is now effected in normal It will be appreciated that, when the water supply is closed olf, a column of water will remain in the drill rods and, in cases where drilling has taken place at great depth, this column of water may produce suicient pressure in the chamber 41 to move the cylinder slightly against the action of the spring 47. This, however, is overcome by the relief ports 34 through which the surplus water is allowed to drain out and through the ports 43.

The core-lifting means described above has many advantages which have not been obtained by existing devices. Chief among these are the following:

(a.) By virtue of the positive retraction of the core gripper from the taper of the bit prior to commencement of drilling operations, this function is no longer performed by the core itself and damage to the core, especially a soft one, is thus greatly minimized.

(b.) The core gripper can be adjusted to assume a retracted position only a short distance from the mouth of the bit, thus allowing the core to enter it at a much earlier stage than has hitherto been possible. This prevents a friable or soft core from spreading in the tapered mouth of the drill bit and does not expose the core to the usual danger of being crushed or ground through the rotary action of the bit.

(c.) The core gripper can also be constructed and adjusted to be jammed between the drill bit and the core at a transverse plane substantially flush with the mouth of the bit. As a result, a clean break of the core flush with the mouth of the drill bit will occur and no stub of the core will be left as is usually experienced.

(d.) The use of water pressure to maintain the core gripper out of engagement with the core, also serves a very useful purpose. If, when drilling, a wedge should occur in the core barrel and threaten to crush the lower part of the core, the pressure gauge on the surface will immediately indicate a drop in the operating pressure to which the core-lifting means has been adjusted, thus warning the drill operator to take action to prevent damage to the core or drill bit.

We claim:

1. In a rotary drill having a core barrel, a hollow drill rod connected at one end to said core barrel, a drill bit connected to the forward end of said core barrel, whereby uid under pressure is passed through said drill rod to said drill bit, core-lifting means within said core barrel and comprising, in combination, a cylinder and a piston therefor, the piston being fixed relative to the core barrel and the cylinder being movable relative to the piston; a contractable core gripper; a mechanical connection between the cylinder and the core gripper; contraction structure within the forward end of the core barrel; a passage within the core barrel for conveying uid under pressure from said drill rod to the drill bit; port means connecting said passage with the interior of said cylinder on one side of said piston and allowing uid under pressure to enter the cylinder to cause the cylinder to move relative to the piston and by virtue of its connection with the core gripper, to move the core gripper away from the contraction structure into an expanded inoperative position and spring means arranged to act against the aforesaid movement of the cylinder and to move the core gripper into engagement with the contraction structure and thus into a contracted operative position in which it will tightly grip the core when tiuid pressure to said cylinder is released or at least substantially reduced.

2. Core-lifting means, according to claim l, including a hollow stem passing through one end of the cylinder in slidable but Huid-tight relationship thereto, said stem being secured at the one end thereof outside the cylinder to the core barrel and at the other end thereof within the cylinder to the piston, and the bore of said stem being connected with the bore of the drill rods to form part of the passage for conveying fluid under pressure from the drill rod to the drill bit.

3. In a rotary drill having a core barrel, a hollow drill rod connected at one end to said core barrel, a drill bit connected to the forward end of said core barrel, whereby fluid under pressure is passed through said drill rod to said drill bit, core-lifting means within said core barrel and comprising, in combination, a tube mounted coaxially and movably within the core barrel in spaced relationship thereto and of internal diameter such that the core to be lifted may be accommodated therein; a contractable core gripper operatively connected to the forward end of such tube; contraction structure located within the forward end of the core barrel and engageable by the core gripper when the latter is moved forward by the tube to cause the core gripper tightly to embrace the core; a cylinder mounted co-axially within the core barrel in spaced relationship thereto and means operatively connecting said cylinder to the rearward end of the tube so as to be movable therewith; a hollow stem which extends rearwardly through the rear end of the cylinder in slidable but fluid-tight relationship thereto and which is fixed at its rear end to the core barrel and the bore of which is connected to the bore of the drill rod to provide an axial passage for uid under pressure from drill rod; a piston within the cylinder carried on the front end of said rearwardly extending hollow stem; a peripheral groove in said piston between the walls of which and the wall of the cylinder an annular chamber is formed; relief ports in the wall of the stern; passages in the piston connecting the relief ports to the annular chamber so as to allow iluid to pass from the axial passage to the aforesaid annular chamber; a second annular chamber formed between the cylinder walls and the walls of the hollow stem and disposed rearwardly of the piston; outlet ports in the wall of the cylinder which, when the cylinder is moved rearwardly relative to the piston, communicate with the aforesaid second annular chamber and permit the passage of fluid to the drill bit through the annular space between the core barrel on the one hand and the cylinder and tube on the other, and which, when the cylinder is moved forward relative to the piston, communicate with the first mentioned annular chamber; inlet ports in the wall of the stem through which iuid may pass from the stem to the second annular chamber to drive the cylinder rearward relative to the piston, said inlet ports having an area substantially larger than either the relief or outlet ports; and an axially disposed compression spring mounted within the cylinder forwardly of the piston and arranged to move the cylinder forward relative to the piston when the fluid supply is closed off.

4. Core-lifting means, according to claim 3, in which said means connecting said cylinder and tube comprises a swivel-head permitting relative rotation therebetween.

5. Core-lifting means, according to claim 3 in which means is provided for adjusting the compression of the spring.

References Cited in the le of this patent UNITED STATES PATENTS 274,740 Douglass Mar. 27, 1883 2,005,819 Blanchard June 25, 1935 2,100,311 Catland Nov. 30, 1937 2,134,886 Oliver Nov. l, 1938 2,457,628 Baker Dec. 28, 1948 2,596,832 Williams May 13, 1952

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