US1643750A - Slips for supporting drill pipes in well-boring apparatus - Google Patents

Description

Sept. 7, E. PEARSON ET AL SLIPS FOR SUPPORTING DRILL PIPES IN WELL BORING APPARATUS Filed Nov. '7, 1925 2 Sheets-Sheet 1 1,643,750 P 1927' E. c. PEARSON ET AL SLIPS FOR SUPPORTING DRILL PIPES IN WELL BORING APPARATUS Filed Nov, '7, 1925 2 Sheets-Sheet 2 Patented Sept. 27, 1927.

UNITED STATES 1,643,750 PATENT OFFICE.

EDMUND CURTIS PEARSON AND JAMES CHILDS, OF WESTMINSTER, LONDON, ENGLAND, ASSIGNORS TO VICKERS LIMITED, OF WESTMINSTER, ENGLAND, A BRITISH COM- PANY.

SLIPS FOR SUPPORTING DRILL PIPES IN WELL-BORING APPARATUS.

Application filed November 7, 1925, Serial No. 67,480, and in Great Britain November 27, 1824.

This invention relates to slips for supporting drill pipes in well-boring apparatus.

In one form of apparatus for well-boring in which the necessary power is derived from a rotary machine, the boring bit or tool is attached to the lowest one of a number of connected lengths of drill' pipe, which drill pipe is in turn screwed to a drive stem of square cross section. This stem passes through a drive bushing fitted into a master bushing, which latter is in turn fitted into a recess in the table of the rotary machine. The whole length of drill pipe and the square stem can be raised and lowered, being for example suspended by a wire rope from a block at the top of a derrick provided with hoisting gear. As the drilling progresses it becomes necessary from time to time to add further lengths of drill pipe to the end of the connected succession or string of pipesin the hole. To enable this addition to be accomplished, the square drive stem is raised along with the drive bushing, bringing the string of pipes up through the table of the machine. It is necessary to support the length of pipes in the hole by means other than the overhead block, and for this purpose fittings called slips made in vertically divided halves are placed in a tapered hole in the master bushing, the said sli s having horizontal teeth in contact with e It is frequently found, however, that the drill pipes arev not truly circular on their outer' circumference, and it is anobject of this invention to ensure that the total weight of the string of pipes shall be evenly dis-- tributed notwithstanding the occurrence of such irregularities, thereby avoiding damage to the pipes.

According to this invention the ta ered annular slips, which are as usual ra ially divided into halves, or otherwise into a plurality of independently movable members, have on their inner surfaces inclined recesses, wherein segments of hardened steel are capable of sliding up and down, the said segments projecting eyond the inner surfaces of the slips and having horizontal or helical teeth adapted to grip the drill pipe to resist the descent thereof. When the slips are lifted each segment is pulled to the top of Rs travel by a boltpassmg through a reand when the slips are lowered into the tapered hole in the table of the rotary drill ing machine so as to surround the drill pipe, each segment is free to fall by gravity to the bottom of its travel, or so far as is permitted but to their maximum radius, thereby freeing themselves from the pipe.

it has previously been proposed, in a pipe lifter having hinged jaws closing on the pipe, to provide toothed segments separately adjustable in inclined recesses in the jaws, but these segments were set by screws to suit a variable but known diameter of pipe instead of being self-adjusting by gravity as in the present invention, and were driven upwards andsupported by springs, instead of being lifted in unison by a lifting plate when disengaging the pipe.

In order that the said invention may be clearly understood and readily carried into effect, the same will now be described more fully with reference to the accompanying drawings, in which Figure 1 represents inelevation one slip of .a pair, provided with horizontally toothed segments.

- Figure 2 is a plan of the said slip.

Figure 3 is air elevation of a pair of slips viewed from a direction at right angles in relation to the view in Figure 1, a portion of one. of these slips being represented in section on the line 33 in Figure 2.

Figure 4 re resents'in elevation a slip provided with he ically toothed segments.

The segments B may be prevented bya ref taining plate C, secured to the tops of the slips, from rising out of the tapered slots .D which are machined in the bore of the slips. Above the retaining plate is a lifting plate E provided with one or more handles F, and

olts or screws G passing throu h elongated clearance holes H in both the lifting plate E and the retaining plate C are screwed into each of the segments, so that when the slips are raised from the ground by the sand handle the segments B are thereby automatically pulled to the tops of the slots D in the slips. The slips are then lowered by hand into the tapered hole in the master bushing'and embrace the'pipe, and the handle F is then released. If the pipe is truly circular and of the correct size the segments B will remain in their highest positions in the slots; but should the pipe not be truly circular certain segments will fall down wards and inwards until all the segments are in contact with the pipe. The string of drill pipes is then slightly lowered, when the teeth of the segments bite into the metal of the pipe and support the whole weight of the string of pipes.

When the additional length of drill pipe has been attached to the string of pipesin the hole the square drive stem is again attached to the string of pipes and the full weight taken on the wire rope. .The whole string of pipes is then raised a short distance by means of the hoist on the derrick. This causes the toothed segments B to press against the retaining plate C so that the slips are lifted ofl their seating in the mas ter bushing, and the slips can then be re-' moved by hand.

Means are rovided to prevent the toothed segments B rom falling down the well in the event of the lifting screws G breaking. For example a pin J (Figure 3) may be screwed into the back of each toothed seg ment B its head projecting into a groove in the sli and a stop K is cast across each groove, the pin J being located an appreciable distance above the stop so that the normal movements of the segments are not affected thereby.

By the use of slips according to this invention the following advantages are obtained, in comparison with slips having integral teeth :-The toothed segments working in tapered slots are free to, adjust them selves to the irregularities of the drill pipe, so that the load is evenly distributed between all the segmeins. These segments can neaavso easily be removed and replaced, thus eliminating the difficulties caused by dull'slips and loss of time in ire-sharpening the teeththereof. It is only necessary that the segments themselves should be made of hardened steel, .as the body of the slips may be of a material which is cheaper and more easily machined.

In the following claims, the expression substantially horizontal teeth. must be understood to include teeth which are'actually horizontal as illustrated in Figure 1, or helical as illustrated in Figure 4.

What we claimQand desire to secure by Letters Patent of the United States is In well boring apparatus arouate' slips adapted to be fitted into a tapered hole in the tajole of a rotary drilling machine for temporarily holding drill pipes in one position, each of said slips being provided with a pluralityof independently movable members, said movable members being composed of segments of hardened steel, capable. of sliding up and down in inclined recesses on the inner surfaces of the slip members, each 1 segment projecting beyond the inner. surface of its slip member and having substantially horizontal teeth adapted to grip the drill pipe to resist the descent thereof, a retaining plate secured to the top of each slip member, a lifting plate located above said retaining plate and having a handle, bolts passing through elongated clearance holes in both the lifting plate and retaining plate, said bolts being secured to the segments, whereby the segments are automatically pulled to the top of their travel when said handle is raised to lift the slip member, and said bolts being of such length as to allow each seg-.

ment to fall by gravity independently of adjacent segments when said handle is released until all the segments bear against the pipe, whereby the load is distributed over all said segments irrespective of whether pipe be truly circular.

EDM. C. PEARSON. JAMES CHILDS.

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