Title:
Well drilling equipment
United States Patent 2126933


Abstract:
This invention has to do with well drilling equipment and is more particularly concerned with equipment for drilling wells through formations where there is present oil or gas pressure of relatively high value, or where it is anticipated that such formations might be encountered. It is not...



Inventors:
Frederick, Stone
Stone, Albert L.
Application Number:
US3569635A
Publication Date:
08/16/1938
Filing Date:
08/12/1935
Assignee:
HYDRIL CO
Primary Class:
Other Classes:
81/91.2, 173/149, 175/171, 175/210, 254/29R, 411/918
International Classes:
E21B19/00
View Patent Images:



Description:

This invention has to do with well drilling equipment and is more particularly concerned with equipment for drilling wells through formations where there is present oil or gas pressure of relatively high value, or where it is anticipated that such formations might be encountered.

It is not uncommon in certain fields to drill through formation which develop an effective well pressure of 3,000 or more pounds per sq. in. In order to control the fluid flow while drilling through such formation, it has become the practice to pack off, near the surface, the annular space between the casing and drill pipe. In going into the hole with the drill pipe and making it up stand by stand, the pipe must thus be passed through the high pressure fluid within the casing. When the length of pipe in the hole is such that its weight is less than that of the effective well pressure tending to lift it, it will be seen that it must be forced down until sufficient "stands" have been added to the top of the pipe to allow the force of gravity to sink it. On the other hand, in "coming out" of the hole, immediately after the balance point has been reached (that is, the point where the pipe has been shortened by lifting it and unjointing stands from the top until the weight of the pipe left in the hole just balances the effective force of the well pressure tending to lift it) the well pressure tends to eject the pipe from the casing.

The forceful entry of the pipe until after the balance point is passed by adding sufficient pipe lengths to overcome the lifting force of the well pressure, is termed "snubbing in", and the conStrol of the movement of the pipe under the influence of well pressure in coming out, is termed "snubbing out". It will be realized that with high well pressures, the lifting force exerted on the pipe becomes tremendous and if not kept under constant control may easily result in disaster, or, at least, in causing great delay and damage., The present invention contemplates the provision of particular efficient means for snubbing well pipe into and out of casing, with an assurance of control over the pipe at all times, and as one feature has a plurality of controlling clamps of such a nature that if one fails another one automatically comes into play.

The device includes up-control slips which may act either automatically or be manually adjusted to prevent upward movement of the pipe under the lifting tendency of the formation pressure when the snubbing means is released between snubbing strokes, and also includes down-control slips which may act automatically or be manually adjusted to check the descent of the pipe if breakage should occur therein above the slips, or in the event of breakage of the cable by which the pipe may be lowered or raised after the "balance point" has been reached in "going in" or before balance point is reached in "coming out".

The equipment has a further feature which automatically prevents damaging action in the following event. Assume there is sufficient pipe in the well to overbalance the effective lifting force of the pressure and that the pipe suddenly breaks at such a point that the broken-off portion extending from the surface is of insufficient weight to overbalance the well pressure. In the absence of control means, this portion would be forcibly ejected from the well with tremendous speed, ordinarily too fast for a human being to take any counteracting action. Furthermore, in the event the drill stem is in tension at the time of the break, it may previously have been stretched to the extent of several feet and the sudden parting will release all the energy stored up during the stretching of the pipe and give added impetus to its upward movement. The up-control slips mentioned above provide means which act automatically to prevent such ejection in spite of the highest pressures which may be encountered.

However, the problem is even greater than merely that of checking the upward rush of the pipe, for such checking tends to cause the pipe to rebound thus loosening the up-control slip which may result in great damage by failure to reset the slips immediately and, at best, putting tremendous strains on the hold-down equipment when the effort to reset is made. With our equipment, however, this rebound action is automatically checked by the down-acting slips, it resulting that the pipe may only move a very short distance in either direction and will finally and positively be brought to rest without excessive longitudinal vibration.

The up and down control slips are manually or automatically shiftable into and out of operating positions through actuation of a single operating lever, or they may both be held by that same lever in neutral or inoperative position. Full stroking of the lever in one direction moves one set of slips to operative position and the other set further from operative position (assuming the two slips were originally in a neutral or inoperative position) while a full stroke of the lever in the opposite diretion reverses the conditions of the two slips.

The invention has many other features of novelty, but these may be pointed out to better ad- 56 vantage in connection with the following detailed description of a preferred embodiment, reference being had to the accompanying drawings, in which: Fig. 1 is an elevational view, partly in broken away section, showing an embodiment of our invention; Fig. 2 is'a detached plan view of a centering thimble used in connection with our device; Fig. 3 is a section on line 3-3 of Fig. 2; Fig. 4 is a fragmentary section on line 4-4 of Fig. 2; Fig. 5 is a fragmentary, enlarged medial sectional view, partly in elevation, of the yoke elements of our device; Fig. 6 is a fragmentary, enlarged medial sectional view, partly in elevation, of the table elements of our device; Fig. 7 is a top plan view of Fig. 5; Fig. 8 is a view showing part of the elements in Fig. 5 but with certain of those elements in. changed relative positions; Figs. 9, 10 and 11 are enlarged views showing part of the elements of Fig. 6, but with certain of those elements in changed relative positions; Fig. 12 is an enlarged section on line 12-12 of Fig. 6; Mg. 13 is an enlarged section on line 13-13 of Fig. 6; Fig. 14 is a section on line 14-14 of Fig. 5; Fig. 15 is an enlarged section on line 15-15 of Fig .5; Fig. 16 is a detached front elevation of a clamp, in closed condition, making up a part of our device; Fig. 17 is a top plan view of Fig. 16; Fig. 18 is a section on line 18-18 of Fig. 17; Fig. 19 is a view similar to Fig. 17 but showing the clamp open; * Fig. 19a is a top plan view of a clamp or slipssetter similar to that of Fg. 17 but turned top for bottom; Figs. 20 to 27, inclusive, are diagrammatic views showing various relative positions of the slip assemblies.

Our invention is adaptable to any suitable type of drilling equipment, though we have illustrated it as applied to a rotary table of the hydraulically raised and lowered type and to a drill pipe which has "flush joint" characteristics.

This choice of illustration, however, is in no way to be taken as limitative on our invention, considered in its broader aspects. So also, while the slips are capable of operating to advantage in connection with any suitable supporting structure or spider, whether or not that structure be capable of rotation or vertical movement, our^ invention has been illustrated as applied in a situation where the up and down control slips are supported by the bushing of a vertical reciprocable, rotary table. In this connection, so far as the operation of our improved equipment is concerned, that bushing is, in effect, a fixed part of the table, and therefore where our claims do not specify the supporting structure as of a particular nature, 'that structure may be considered as of any suitable type and not as limited to the showing.

Numeral 10 indicates generally a rotary table assembly or, what may be more generally termed a supporting structure or spider for the control slips later to be described. This table is disposed centrally over well casing II and is adapted to operate the hollow drill stem or pipe 12 made up of sections 13 connected by tool joints 14, and carrying at its lower end a bit or other tool 15 of slightly larger diameter. A conventionally indicated packer 16 packs off the bore 17 of casing II about pipe 12, though it allows vertical reciprocation and rotation of the pipe therethrough. The well fluid and the return column of circulating or drilling fluid (which drilling fluid is initially passed downwardly through the bore 18 of stem 12, past check valve 18', and out through the lower end of tool 15 at 15') passes outwardly 1i0 from the casing bore through pipe 19 to any suitable treatment apparatus or storage facilities (not shown). Numeral 20 indicates conventionally a valve for controlling the flow through line 19. Swivel 21 provides for the introduction of circulating or drilling fluid to bore 18, and also provides the means whereby drill pipe 12 is held suspended, lowered, or raised by tackle 22 which leads to usual hoisting drum and brake equipment (not shown).

We will describe in some detail the particular rotary table or slip supporting structure here illustrated in order better to describe a physical embodiment of our invention, without intending in any way to.limit the broader aspects of that invention to the showing or description. Pistons and piston rod assemblies 23 are mounted for vertical reciprocation within cylinders 24 and carry head 25 upon which rotary table 26 is mounted. Fluid pressure admitted selectively to the tops or bottoms of cylinders 24 by control of valves 27, 28, in lines 29 and 30, respectively, causes or controls the vertical reciprocation of head 25 and hence table 26. Table 26 is mounted for rotation on bearings 31 (Fig. 6) supported on internal flange 32 of head 25, sleeve bearings or bushings -33 serving to maintain the table and particularly its sleeve portion 34 which defines table bore 9, in proper alinement. Bearings 35 interposed between the underside of flange 32 and the top of sleeve-carried flange 36, hold the table against upward separative movement with respect to head 25. Table 26 has an internal ring gear 37 whereby the table is rotated through pinion 38 on shaft 39, the latter being powered from any suitable source (not shown).

The upper end of bore 9 is provided with offset sockets or ways 40 (Figs. 12 and 13) which take keys or head portions 41 of the split table-bushing 42, the bushing thus being fixed against rotation with relation to the table so rotary drive imparted to the table is transmitted to the bushing.

The lower shoulders 41' of heads 41 (Fig. 9) 45 engage table 26 in a manner to prevent the bushing from dropping through the table bore, while locking pins 43 (Figs. 9 and 13) which are'mounted for horizontal reciprocation through table walls 44, are adapted to be projected into sockets g6 45 provided, one each, in halves 42a and 42b of bushing 42, the locking pins thus releasably holding the bushing from being lifted clear of the table. Pins 43 are adapted to be reciprocated to and from locking or projected positions by vertical stub shafts 47 (Figs. 6 and 13) which have gear teeth engagement- 48 with rack teeth 49 on pins 43. Shafts 47 may be rotated by a socket wrench applied in their axial sockets 47' (Fig. 12) which are exposed at the top of the table. As will be later described, pipe or work gripping means are mounted in bushing 42 whereby that work may be held against rotation and against vertical movement with respect to. the bushing, it following that rotation of the table through gears 38-37, or vertical reciprocation imparted to the table through the control of fluid flow through cylinders 24, imparts like movement to the pipe and thus the pipe may be raised or lowered through the casing bore, and bit or tool 15 may be rotated to perform operations within the casing bore.

Bushing 42 becomes the direct support for certain wedge slips or work gripping assemblies to be described. But, as mentioned at the forepart of the specification, since this bushing is fixed against movement with respect to table 26, that table (and this is true whether or not the table is rotatable or vertically reciprocable since it may more broadly be considered as a "spider") may be considered as the supporting means for the work gripping assemblies, and broadly speaking, the bore characteristics of the bushing might just as well be considered as formed directly in the bore of the table, so far as our broader claims are concerned.

However, for purposes of describing the illustrated embodiment of the invention, reference will be had to bushing 42 as the supporting member for the slips or as a slip-receiving body member. This body member has oppositely tapering, conical sockets or bores 50 and 51, (Figs. 6 and 9) the wall 52 of the upper socket converging inwardly and downwardly, and the wall 53 of the lower socket converging inwardly and upwardly.

An annular groove 54 is provided at the junction of bores 50, 51, within which groove is seated a thimble 55 for centering stem 12. The thimble is removable in order to clear the bore of the bushing for passing'shoulder members, such as bit 15, therethrough, and also to permit the substitution of different sized thimbles to take work of different diameters. In Figs. 2, 3 and 4 we have shown the preferred form of thimble, this being in the nature of a halved ring having its inner peripheral wall oppositely chamfered as at 56. Ring-halves 55a and 55b are hingedly connected at one side by link 57. When the halves are swung together, the ring is of sufficiently small diameter to be passed through the smallest portion of the bushing-bore. When it has been lowered to a position of horizontal alinement with groove 54, the free ends 58 are spread apart, thus projecting the ring-halves into the groove. This spreading is accomplished .by taking up screw 59 which connects the oppositely tapered wedge blocks 60 interposed between the free ends of the ring-halves, the inclined faces 61 of the wedge block camming the ends of said halves apart in 35 an obvious manner and then serving to hold them apart so the ring is maintained in position within groove 54.

Within socket 50 is provided the wedge slip assembly or radially expansible and contractible C:1 work gripping means generally indicated at C, this assembly (Figs. 9 and 13) being made up of segmental wedge slips 62 (provided in any suitable number, here shown as three) each having a vertical, serrated face 63 in which the teeth preferC5 ably point upward, while the opposite face 64 extends at an angle complementary to and is adapted to engage socket wall 52. As is true in all slips of this character, the inclined face of each slip is cut back at 64a (Fig. 13) so the actual area of contact with the socket wall is reduced for rea-i sons well understood in the art. However, in order to avoid confusion in the vertical sectional views, this clearance is omitted. Each slip has a tongue or dove-tail key 65 extending longitudinally along face 64 and entered in a complementary way 66 (Figs. 11 and 13) sunk in wall 52.

Keys 65 hold the slips against rotation with respect to the bushing, and, with tlhe described type of interconnection between slips and bushing, it will be seen when the slips are moved vertically in either direction they simultaneously move radially of the body or bushing inwardly or outwardly. Thus, when slip-assembly C is raised, it may be considered as radially expanding or moving toward release position, and when the assembly is moved downwardly it may be considered as moving into radially contracted or work gripping position. When assembly C is in this last named position (see Fig. 9) it will be seen that stem 12 is held from dropping downwardly with respect to the table, that upward movement of the table will act through the slips assembly to lift stem 12, and rotative movement of the table will impart like movement to the work through bushing 42 and the slip-assembly C. Slip-assembly C may thus be considered as down-control gripping means.

An up-control gripping means or slip-assembly generally indicated at D is mounted within socket 51 and, with the exception of certain characteristics to be described and the fact that the teeth .of its serrated faces 68 point downwardly, is generally similar to assembly C. The individual slips 69 of this assembly have outer walls 7O which are complementary to and adapted to engage socket wall 53 and have keys 71 sliding within key ways 72 (Fig. 9) which are similar, respectively, to keys 65 and way 66, respectively. With this mounting in effect, it will be seen that upward vertical movement of assembly D moves that assembly into radially contracted or work gripping position, while downward movement of the assembly causes it to move to radially expanded or inoperative condition.

Surrounding stem 12 with annular clearance and at a point above assembly C, is a slip-suspension ring 75 (Figs. 9 and 12) disposed over segmental slips 62. A two-part shifter ring 17, made up of halves bolted together at 76, loosely encircles ring 75, being received within ring-groove 79. Diametrically opposite trunnions 80 on shifter 7' are taken within the slots 8 provided on the ends of forked arms 82, the latter being formed integrally with operating lever 83 which is pivotally and removably mounted at 84 on bracket 85. Bracket 85 is detachably held to head 25 within a socket 86 (Fig. 6) on the latter. Bracket 85 and arm 83 are thus held stationary with respect to head 25, but ring 75 is capable of rotation within shifter 77, so the lever and its connections do not prevent relative rotation between head 25 and table 26 with its appurtenances. In the drawings arm 83 and bracket 85 are displaced from their normal positions to bring them into the same viewing plane as the rest of the table-mecha- 6 nism, and therefrom the arm is shown as though a portion were broken out to avoid interference with the yoke piston rod, to be described.

Ears 90 depend from ring 75 toward the underlying slip segments 62, a pin 91 connecting the upstanding lug 92 on each slip segment with the corresponding ear 90. Pins 91 extend through slots 93 in ears 90, these slots allowing for the relative horizontal shift of the wedge segments with respect to the lifting ring when said segments are raised or lowered, and preferably the slots incline downwardly and outwardly, as clearly shown in Fig. 9, so their lower walls 94 may have camming action against pins 91 when the lifting ring is raised and thus aid in spreading the segments relatively apart as the slip assem bly is lifted., Lever 83 terminates in handle 95; adjacent tb which, under certain operating conditions, ther may be applied a weight 96 which tends to ro tate lever 83 in a clockwise direction, as viewec in Figs. 6 or 9. Weight 96 may be suspendec from lever 83 by hanger bolt 97 and may includ( provision for adding or taking away fractiona weight elements 98 to secure proper balancinE effect.

Suspension bolts 100 (Figs. 6, 9, 12 and 13) depend from ears 101 on ring 75, extending, witt lost-motion clearance 101' through that ring through clearance holes 102 in bushing 42 and through clearance holes 103 in ring 104 which encircles stem 12, with annular clearance, below slips 69. Bolt heads 105 and nuts 106 thus support ring 104 in vertically spaced relation with respect to ring 75, limiting the extent of downward movement allowed to slips 69. However due to the loose mounting of the suspension bolts within the rings said rings are capable of independent movement, within certain limits, the purpose of which will be hereinafter made apparent.

For the purpose of setting forth the operation of the slip mechanism so far described, reference will first be had to Pig. 6. Weight 96 has such effective force in tending to swing lever 83 in a clockwise direction in that figure that it just slightly overbalances the weight of the two slips assemblies and all appurtenances supported thereby, some of which are yet to be described. Accordingly, in Fig. 6 to which reference is now being made, it is assumed that the operator is holding up slightly on handle 95, just sufficiently to overcome the otherwise overbalancing effect of weight 96 and to maintain assemblies C and D in neutral or release positions, both of these assemblies being radially expanded to an extent where their serrated faces clear pipe 12. Now if handle 95 be depressed or if the operator merely releases his hold on that handle to allow weight 96 to exert its full force, the clockwise rotation of lever 83 acts to raise ring 75, (Fig. 11) thus lifting slips 62 and spreading them radially outward to a greater extent, and, through suspension bolts 100 and lifter ring 104, raising assembly D and thus radially contracting it so its individual slips 69 are driven into wedging and biting engagement with stem 12.

If, on the other hand, starting from the neutral position of Fig. 6, handle 95 be raised, the counterclockwise movement of lever 83 lowers assembly C into socket 50 (Fig. 9) and hence into a position of radial contraction and wedging engagement with the pipe, and, through bolts 100 and ring 104, further lowers assembly D so its individual slips 69 spread further apart to positions of full radial expansion. Situations in which these operations are performed and the conditions which they bring about, will be discussed later.

It will be noted however, that when the slips assemblies are lowered by counterclockwise rotation of the operating handle to set, the upper slips assembly C and to lower assembly D to a position of full expansion (Fig. 9) the sliding fit between ring 104 and bolts 100 will allow subsequent movement of assembly D upwardly independently of assembly C and into set position if lifting force be applied independently to ring 104. If the slips assemblies both be in neutral position (Fig. 6) the sliding fit between ring - 104 and bolt 100 also allows movement of assembly D to work-gripping position by independent o lifting force applied thereto, without affecting ase sembly C, as will appear.

- Rings 75-104, and bolts 100 taken together d may thus be considered a slip carriage or actud ating assembly R (Fig. 6) controlled by lever S83, whereby both the upper and lower slips may l be simultaneously shifted in a manner to set Sone assembly and release the other, or may be utilized to hold the assemblies in neutral positions, or to allow the slip assemblies to be operated Sindependently by means now to be described.

SAn automatic setter for assembly D is indiScated generally at E (igs. 6, 9 and 16 to 19, in- 12 i elusive) this setter being in the nature of a reSleasable clamp carrying auxiliary wedge slips S110, the tapered body and teeth of which point in the same direction as slips 69 and their teeth 68. Slips setter E consists of a tubular body III made up of halves 112 and 113 pivotally connected at 114 and each provided with external flange 115. Bracket flanges 116 (Fig. 9) preferably welded or otherwise suitably attached to the underside of ring 104, extend, one each, beneath flanges 115 to support the setter from the ring, or more broadly, from carriage R, but sufficient clearance is provided to insure that flanges 115 may slide horizontally over brackets 116 to enable the opening and closing pivotal movement of halves 112, 113 and also to allow the entire assembly E, when clamped to stem 12, to rotate with that stem and with respect to carriage R under such operating conditions as may occur during rotation of pipe 12 with respect to table 26. Wedge slips I 10 are mounted for vertical reciprocation through ways I 17 (Fig. 18) in body member I 11, the radialoutward.faces 118 of these ways inclining inwardly and upwardly and the slips having lateral keys 119 entered in complementary ways 120. It follows that vertical movement of slips 110 is accompanied by horizontal translation thereof, they moving radially inward toward operative or gripping position when they are shifted upwardly through the ways, and being radially retracted to expanded or inoperative position when they are moved downwardly through the ways. The extent of vertical movement allowed to slips 110 is established by a ring-half 121 bolted at 122 to each half of the body member, and weld-plug 123 provided at the upper end of each way.

• At the free end of body section 112 a trunnion block 124 is pivotally mounted in vertically spaced ears 125, keeper straps 126 being welded across the openings of ear-notches 127 to maintain trunnion pins 128 in said notches. The threaded shank 129 of eye bolt 130 extends, with clearance, through trunnion block 124, a pin 131 pivotally connecting the eye 132 of bolt 130 with the fork arms 133 of operating lever 134, the latter being pivotally connected at 135 with ears 136 on bodyhalf 113. Compression spring 137 on bolt 130 is interposed between block 124 and adjustment and lock nut 137', 138, respectively, while the bolt also carries an adjustment and lock nut 139 and 140, respectively, at the other side of block 124.

When lever 134 is swung to the position of Fig. 17, bolt 130 is drawn to the right and acts through nut 137' and spring 137 to draw halves 112 and 113 into closed or operative position, the power of spring 137, as regulated by adjusting nuts 137' and 138, being such that slips 110 are frictionally engaged with stem 12 when said slips are in the lowermost position, as in Fig. 18. However, the 7s spring is adjusted so it will not close the body with sufficient tightness to cause -any appreciable biting engagement of the slips 10 with the pipe and will allow downward movement of the pipe with respect to the slips, but upward movement of the pipe will lift the slips into wedging positions. If there be any irregularities on the pipe surface such as would tend to spread the body halves apart during downward movement of the pipe, spring 137 allows this slight spreading action to take place without damage to any of the clamp parts.

It will be noted that when lever 134 is in the position of Fig. 17, pin 131 has passed behind a line common to centers 128 and 135, a self-lock Sthus being accomplished. However, in order to insure against any possibility of accidental release, a locking pin 141 may be dropped through holes provided in arms 133 and behind lug 142 on eye 132, which will prevent clockwise movement of lever 134, as viewed in that figure. A storage socket 143 on lever 134 takes pin 411 when not in use and the pin may be chained to the handle as at 144 to prevent its loss.

Assuming now the slip assembly D is in the condition of Figs. 6 or 9 and setter E is in the condition of Figs. 6, 9 or 18, if pipe 12 starts upwardly under the influence of well pressure from below, the frictional engagement of slips 110 with pipe 12 will cause those slips to be carried upwardly along with the pipe and thus be wedged between the pipe and body I 1, resulting finally in lifting that body and with it the ring 104, sliding that ring upwardly along bolts 100 and hence wedging slips 69 between pipe 12 and bushing 42 to radially contact assembly D (see Fig. 10) and thus check further upward movement of the pipe with respect to the table bushing.

When setter E is in the closed position of Fig. 17, nut 139 is spaced from block 124 so as to avoid interference with the body-closing action of spring 137. However, with key 141 removed, clockwise rotation of lever 134 towards the position of Fig. 19 moves nut 139 into contact with block 124, whereupon further movement of the lever forces open the setter body, thus clearing slips i 0 from pipe 12.

The automatic setter for the down-control slip assembly C is indicated generally at B and is of the same construction as setter E but is turned top for bottom (Fig. 19a) so that its slips 150 (Fig. 9) point in the same direction as slips 62 and so its teeth 15 point in the same direction as teeth 63. Since the structure is otherwise the same, similar numerals except for the addition of the exponent "a" have been applied to its elements, so the above description of setter E may be applied to the structure of setter B.

Flanges I i 5a here rest on top ring 75, the flange on one body half I 13a preferably being welded at 113' or otherwise suitably secured to the underlying lifter ring 75. However, this ring is preferably capable of sufficient horizontal movement with respect to bolts 102 and shifter 77 to allow Sthe wedge segments 150 of the clamp half which is welded to ring 75 to be cleared from pipe 12 when the setter is fully opened up to a position corresponding to Fig. 19, though of course in this case the setter is reversed side for side with respect to the showing in that figure. When setter B is closed, as in Fig. 19a, its spring 137a maintains slips 150 in frictional contact with the pipe 12 but does not prevent upward movement of said pipe with respect to the setter or, considered otherwise, does not prevent the downward movement of assembly C with respect to bushing 42 or downward movement of carriage R. However, should the pipe suddenly start to drop due to breakage above the table, the pipe will carry slips 150 with it, wedging them between the pipe and body lia (Fig. 9) and then carrying setter B, ring 75, and slips assembly C downwardly, overpowering weight 96, and thus causing slips assembly C to be radially contracted into operative or gripping positionAnd thereby preventing further descent of pipe 12.

In this connection it will be noted that where weight 96 is not employed, the operator must exert a continuous pressure downwardly on handle 95 in order to hold slips assembly C out of work gripping or operative position, and under such conditions if the operator should release his hold on handle 95, slips assembly C will drop and thus be automatically set to prevent dropping of the pipe. However, when weight 96 is used, it is preferable (though not necessary) that setter B be closed about the pipe during all periods except when the pipe is being intentionally lowered or when table 26 is being raised, with the pipe remaining stationary, (as during actual drilling-head operation) so slips assembly C will be automatically set by setter B in the event of breakage above the table which would otherwise allow the pipe to drop, for, if the operator fails to lift handle 95 under those conditions, or if he releases his hold on the handle, as he is very apt to do in his attempt to "get out from under" in the event a break suddenly occurs, weight 96 would prevent the setting of slips assembly C. ' The equipment so far described is fully operative irrespective of the means used for "snubbing in' or "snubbing out" the pipe, or it may be used where snubbing operations are not being actually employed but where there is a possibility that excessive well pressures may be reached in drilling down. We will now proceed to describe a particularly effective type of snubbing mechanism which is novel, not only in itself, but also in association with the slip and slip operating mechanism above described and which, during the snubbing in or out operations may be considered as a part of the snubbing equipment.

Numeral 160 indicates generally a snubbing yoke made up of two side bars 16 which are spread apart at their centers to take drill pipe 12 and certain clamping mechanism, and are brought together at their ends, bolts 162 and spacer blocks 163 holding the side bars in proper fixed position.

The yoke is'supported on piston rods 164 carrying pistons 165 (Fig. 1) which are mounted for reciprocation within cylinders 166, here shown as being attached through heads 167 to the stationary cross head 168 provided at the top of cylinders 24. By admitting fluid under pressure alternately to the opposite ends of cylinders 166 through lines 167' 6 and 168', as controlled by valves 170 and M7I, respectively, yoke 160 may be reciprocated or controlled in its reciprocation.

Preferably, the upper section 172' (Fig. 5) of each piston rod 164 is detachably connected as at g6 I'7, so the yoke may be readily removed from or attached to the equipment during different phases of operation. Brackets 174, welded to sections 172, carry at their upper edres guide flanges 975 to take the lower edge of yoke 160 while adjusting screws 177 carried by the brackets engage the under side of the yoke to allow for proper lining up of the yoke and piston rods and for maintaining them in proper relation.

The yoke clamp or slips assembly is generally 7 indicated at A and Includes a tubular body member or slips-socket 178 which is flattened at 179 (Fig. 15) to fit between yoke arms 161, and has a heavy base flange 180. Head casting II1 has a bore 182 in alinement with the bore 183 (Fig. 5) of body 178, and preferably is made up of halves 181' (Fig. 14) bolted together at 184, the halves being individually welded to the underlying yoke arms 161. A head flange 186 has a depending tubular portion 187 which fits within the bore 182, and compression bolts 188 extend from flange 188 to flange 180, serving to hold body 178 up and to hold flange 186 down against opposite sides of bars I61, thus rigidly tying together all the parts so far mentioned. In Figs. 5 and 8, a section of pipe 12 has been broken away to disclose parts which would otherwise be hidden thereby.

Tube 189 is mounted in the bore of flange 186 and its extension 181 for vertical reciprocation, this tube functioning as a slips-releaser, or de_presser, as will appear. Welded to the lower end of tube 189 is a collar or shoe 190 having a plurality of angularly spaced slips-depressing fingers 191 which project downwardly into slip ways 192 5 (Fig. 15) in body 178. These slip ways are provided in any suitable number and their radially outward faces 192' incline upward and inwardly as clearly indicated in Fig. 5. Since these ways open to bore 183, their Inclined faces may be con0 sidered together as defining inwardly and upwardly converging walls.

Slips 193, one for each way, are mounted for vertical reciprocation with respect to body member 178. Their inner faces are serrated with -3 downwardly pointing teeth 194 while their outer faces carry lateral tongues 195 (Fig. 15) engaged Sin complementary grooves 196 which open to ways 192. It follows that vertical movement of the slips causes simultaneous horizontal translation thereof, so upward movement of slips assembly A with respect to body member 178 radially contracts the slip assembly, and downward vertical movement of said assembly causes simultaneous radial expansion thereof.

5 Engaging the top of tube 189 is a cross head 200 from which extend the diametrically opposite bolts 201, the latter passing with clearance through holes 202 in flange 180 and through holes 203 in plates 204, the latter being welded on top of flange 180. Bolts 201 carry at their lower ends 50 a slip-supporting and setting ring 205 which extends horizontally beneath the lower ends of slips 198. On the other hand, fingers 191 engage the upper ends of slips 193, it following that vertical Smovement of the slip carriage generally indicated at T (and made up of cross head 200, tube 189, fingers 191, ring 205, and bolts 201) in either direction with respect to the yoke and body 178 causes coincident vertical and horizontal moveSment of the slips and thus moves them into and out of gripping or release positions. Thus, the slip assembly A is radially contracted or moved into setting position by upward movement of carriage T and is radially expanded by down movement of that carriage. Individually, ring 204 may be considered as a slips setter, and fingers 191 as slips depressers or releasers, and the slips are depressible to an extent that their radial movement is sufficient to open up a bore of a size to pass shoulder elements on pipe 12, such a bit 15.

Compression springs 206 encircle bolts 201 between cross head 200 and plate 204 and thus tend constantly to raise carriage T and move slips assembly A to operative or gripping position.

However, during certain phases of operation, it becomes necessary or desirable to h6ld the carriage in its lowermost position against the action of spring 206 and thus hold the slips assembly A In radially expanded or released position. While any suitable type of latch may be employed, we have here illustrated a bar or latch member 210 which is pivoted at 211 to lifter ring 205, spring 212 tending constantly to rotate this latch in a counterclockwise direction as viewed in Fig. 5.

Throughout the normal stroke ofr carriage T, the edge 213 of latch 210 merely slides along the lower corner of flange 110, but if ring 205 be separated from flange 180 by more than its normal stroke, for Instance, by holding down on cable loop 214 (depending from ring 205) while yoke 160 is raised, spring 212 will rotate latch 210 beneath flange 180, notch 215 being provided for the reception of the flange corner, and the latch thereafter prevents upward movement of the carriage to return the slips to operative or radially contracted position until said latch is manually released by swinging it against the action of spring 212. This release may be accomplished even though the yoke be near the upper limit of its stroke, through the medium of cable 216 applied through link 217 to offset lug 218 on latch 210.

Without attempting to discuss all the various manners and situations in which our equipment may be used, we will describe briefly a few typical operations. For this purpose reference will be had particularly to Figs. 20 to 27, inclusive, wherein the elements are indicated diagram,matically. In these views, where the slips are shown in dotted lines they are to be considered as out of engagement with the drill stem (for instance, clamps B or E would be open, as in Figs. 6 and 19, respectively; slips A would be' _.latched open, as in Fig. 8, and assemblies C or D would be out of pipe engaging position, for instance in the neutral position of Fig. 6); where the slips are indicated in full lines but with no hatching within them they are to be considered as engaging but not gripping the drill stem, so they will allow the stem to slide or "ratchet" through them in one direction, but will grippingly engage the stem if it starts in the other direction, (for instance, clamps B or E would be closed but the slips therein would be relatively radially expanded); and where the slips are indicated in full lines with hatching within them, they are to be considered as being wedged into gripping engagement with the drill stem.

Figs. 5, 6 and 20 illustrate the condition of parts on the down-stroke of the yoke in "snubbing-in".

In this situation, the operator holds up on handle 95 to maintain assemblies C and D in the neutral Positions of -Mg. 6. It will be seen that yoke slips A are gripping the work and the yoke e s thus adapted to forcibly depress the drill stem, no resistance being offered by the table slips which are all open or neutral except assembly E and this latter,'though closed, allows the pipe to be lowered without interference, for it is in the condition of Fig. 6. However, if the stem breaks between A and B (so A would no longer be effective to hold the stem down against well pressure) assembly E will be carried up by the pressurelifted pipe and will set assembly D, as has been previously described, to check further upward movement of the pipe. Or if the operator depresses handle 95 or if he drops the handle and thus allows Weight 96 to act, the resultant upward movement of carriage R will set assembly D, leaving E in the condition of Fig. 11. When assembly D is automatically set by the unward movement of setter E (Fig. 10) assembly C will remain in its neutral position, for ring 104 will merely ride up on bolts 102. Where assembly D is set by depression of handle 95, either manually or by allowing weight 96 to act automatically (Fig. 11), assembly C will be lifted higher to a position of full radial expansion.

As the yoke starts up to take a new bite on the pipe, the well pressure acts to raise the pipe and setter E along with it, thus setting assembly D, as has been described, and the parts are in the condition of Fig. 21, setter B either being left open or being manually closed, as the'driller may elect, but in neither event does it resist upward movement of the pipe. As soon as upward movement of the pipe is checked by assembly D, further upward movement of the yoke has the effect of depressing fingers 191 to withdraw slip-teeth 194 from biting engagement with the pipe, whereupon carriage T travels upwardly with the yoke and slips 193 "ratchet" over the pipe, ready to take a new grip when the yoke starts down again. If, during the upstroke of the yoke, assembly D fails for any reason, the upwardly forced pipe will carry yoke slips I 9 with it and thus set them in a manner to put the pipe under the control of the yoke. If, as a precaution, setter B has been closed during the upstroke of the yoke, it must be reopened before the downstroke :is started. After the "balance point", as defined above, has been passed, the pipe is lowered in by cable, in which case the elements are put in the condition of Fig. 22, the yoke slips either being latched open (in a manner to be later described in connection with another operation) or the yoke entirely removed. In this case assemblies C and D are held in neutral or release positions (Fig. 6) setter B is opened, and setter E is closed, thoughit does not resist downward movement of the pipe. If, however, the pipe breaks below E, so the weight of the upper broken-off portion thereof is insufficient to overcome the well pressure tending to lift it, setter E is carried up by the pipe and automatically sets assembly D, as previously described. If setter E should fail or if it happened to have been left open, the operator, merely by dropping handle 95 and thus putting lever 83 under the control of weight 96, may cause an elevation of carriage R and thus set slips D.

Fig. 23 illustrates a situation where the stem is supported in slips assembly C and being rotated by them through table-rotation, it being assumed either that weight 96 has been removed or that the operator is lifting handle 96 to lower assembly C into operative or set position. In the event of a breakage such as that described in connection with Fig. 22, setter E will act to set assembly D, also as described in connection with that figure. Assembly C will check such rebound of the pipe as may be caused by the action of assembly D in suddenly checking the up-rush, and the pipe will thus be brought to rest with minimum longitudinal vibration and with minimum extent of travel in either direction. If weight 96 has been left on lever 83 during this period and the operator releases his hold on handle 95 (which otherwise would result in assembly-C going to full release position) setter B will come into play as the pipe starts down on its rebound stroke and thus automatically set assembly C, in spite of weight 96, and check the rebound. However, the finally predominant uppressure will leave the several assemblies in the relative positions of Fig. 24, for the pipe on its last upstroke will clear setter B and assembly C from gripping engagement therewith and weight 96 will become effective to raise both of them.

Fig. 25 illustrates the condition of elements when pulling the stem out by cable before the "balance point" is reached. Assemblies C and D are in release position, setter E is open, while setter B is closed and in condition to "ratchet" to allow the lifting of the pipe, though it will automatically set assembly C if the pipe starts to drop.- If the pipe breaks and the well pressure becomes effective to eject the pipe, the operator need merely depress or drop handle 95 which will cause the setting of assembly D.

Fig. 26 illustrates the up-stroke of the yoke in the "snubbing out" operation. Assemblies C and D are held in neutral position, setter E is open (as in Fig. 19) and setter B may be closed or not, as the operator desires. Since yoke slips A are in work-gripping position, the upward movement of the pipe is controlled by regulation of the fluid pressure within cylinders 166. Just before the yoke reaches the top of its stroke, the operator closes setter E and holds down on cable 284, thus holding ring 206 and carrier T stationary while the yoke continues upwardly, freeing slips 092 from the pipe. As the end of the yokestroke is more nearly approached to increase the separation between flange 180 and ring 205, spring 212 rotates latch 210 beneath flange i80 to hold them separated and thus latch the yoke slips o3 down in expanded or release position.

Since setter E has been closed it will have been effective, under the influence, of the pipe as lifted by well-pressure, to set assembly D and thus hold the pipe from further upward movement after assembly A has been released, so, with the yoke slips latched down, (Fig. 27) the yoke may be lowered to take a new bite, whereupon cable 216 is pulled to swing latch 2 0 from holding position and thereby allow springs 206 to act to elevate carrier T and' reset slips 193 on the pipe. Thereafter, clamp E is re-opened and the "snubbing out" cycle repeated.

There are many other situations in which the equipment plays an important part, but it is believed the above illustrations will suffice to point out the cooperation between elements and the general utility of the equipment. However, various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claims.

We claim: 1. In combination, a supporting structure having an upwardly and inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable upwardly therethrough from inoperative position into pipe-engaging position, a carrier for said assembly and engaging it from beneath, means for shifting said carrier vertically to move the o6 assembly into pipe-engaging position, said means embodying a member applied to the pipe and to the carrier and adapted automatically to move said carrier and thereby the assembly upwardly upon initial upward movement of the pipe; a snubbing yoke mounted for vertical reciprocation above the supporting structure and having a bore adapted to take the pipe, and releasable pipe-gripping elements carried by the yoke.

2. In combination, a supporting structure having an upward and inwardly tapering bore adapted to take a vertically extending pipe, a Wedge slip assembly within the bore and movable vertically therethrough into and out of pipe-er gaging position, a carrier for said assembly-and engaging it from beneath, and means applied to said pipe and to said carrier and operable upon initial upward movement of the pipe to elevate said carrier and thereby move said assembly into pipe-engaging position.

3. In combination, a supporting structure having an upwardly and Inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough into and out of pipe-engaging position, a carrier for said assembly and engaging it from beneath, manually operated means for shifting said carrier vertically, and means applied to said pipe and to said carrier and operable independently of said manually operated means upon initial upward movement of the pipe to elevate said carrier and thereby move said assembly into pipe-engaging position.

4. In combination, a supporting structure having an upward and inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough into and out of pipeengaging position, a carrier for said assembly, and means applied to said pipe and to said carrier and operable upon initial upward movement of the pipe to elevate said carrier and thereby move said assembly into pipe-engaging position, said means embodying a tubular body member connected to the carrier and having a bore through which the pipe extends, said last named bore tapering upwardly and Inwardly, and wedge slips in said body bore and about the pipe.

5. In a device of the character described, a supporting structure having a bore whose upper portion tapers upwardly and outwardly and whose lower portion tapers downwardly and outwardly, a pair of wedge-slip assemblies complementary to and entered, one each, In said bore-portions, and a removable pipe-centering thimble supported by the structure between said assemblies.

6. In a device of the character described, a supporting structure having a bore whose upper portion tapers upwardly and outwardly and whose lower portion tapers downwardly and outwardly, a pair of wedge-slip assemblies complementary to and entered, one each, in said boreportions, and a removable pipe-centering thimble supported by the structure between said assemblies, said thimble embodying a parted ring, and means for spreading the ring-parts into a groove opening to said bore.

7. A centering thimble embodying a parted ring, a pivotal connection between one set of opposed ring-ends, a wedge entered between the other set of ring ends, and means for urging the wedge between said ends to swing the ring parts about the pivotal connection.

8. In combination, a supporting structure having an upwardly and inwardly tapering bore adapted to take a vertically extending pipe, a suspension ring about the pipe above the bore, means for reciprocating said ring vertically along the pipe, suspension elements depending from the 05 ring, and a wedge slip assembly within said bore and about the pipe, a second ring carried by said suspension elements and supporting said assembly, and a releasable pipe clamp carried by said second ring and engageable with said pipe, said clamp being adapted to move the assembly upwardly independently of the first ring, by virtue of initial upward movement of the pipe.

9. In a device of the character described, a supporting structure having a vertically tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable Svertically therethrough in one direction from inoperative position into pipe-engaging position, and means applied to said pipe and said assembly and operable upon initial movement of the pipe in said one direction to move said assembly in said one direction, said means embodying a setter-body associated with said slip-assembly and having a bore through which the pipe extends, said last named bore tapering in the same direction as the first named bore, and wedge slips in said body bore and about the pipe.

10. In a device of the character described, a supporting structure having a vertically tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough in one direction from inoperative position into pipe-engaging position, and releasable means applied to said pipe and said assembly and operable upon initial movement of the pipe in said one direction to move said assembly in said one direction, said means embodying a setter-body associated with said slip-assembly and having a bore through which the pipe extends, said last named bore tapering in the same direction as the first named bore, and wedge slips in said body bore and about the pipe.

11. In a device of the character described, a supporting structure having a vertically tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough in one direction from inoperative position into pipe-engaging position, and means applied to said pipe and said assembly and operable upon initial movement of the pipe in said one direction to move said assembly in said one direction, said means embodying a setter-body associated with said slip-assembly and having a bore through which the pipe e'-*cds, said last named bore tapering in the samq direction as the first named bore, and wedge klips iA said body bore and about the pipe, said setter body being made up of a plurality of connected segments, and releasable means for holding the 46 segment-assembly constricted about'the pipe.

12. In a device of the character described, a supporting structure having a vertically tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough in one direction from inoperative position into pipe-engaging position, and means applied to said pipe and said assembly and operable upon initial movement of the pipe in said one direction to move said assembly in said one direction, said means embodying a setter-body associated with said slip-assembly and having a bore through which the pipe extends, said last named bore tapering in the same direction as the first named bore, and wedge slips in said body bore and about the pipe, said setter body being made up of a plurality of connected segments, and yieldable' means for holding the segment-assembly constricted about the pipe.

13. In a device of the character described, a 6 supporting structure having a vertically tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movw' able vertically therethrough in one direction from inoperative position into -pipe-engaging position, and means applied to said pipe and said assembly and operable upon initial movement of the pipe In said one direction to move said assembly in said one direction; said means embodying a setter body connected to the slip assembly in a manner to impart vertical movement thereto and capable of rotation with respect to the assembly, and pipe-engaging members carried by said body. 14. In a device of the character described, a supporting structure having an upward and inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough into .t and out of pipe engaging position, a carrier for said assembly, a suspension member for the carrier and extending upwardly to a point above said supporting structure, means for lifting the suspension member to move the slip assembly into operative position, said assembly being movable upwardly independently of the suspension member, and a slip setter below the slip assembly and engaged with the pipe, said setter being adapted to move said assembly upwardly upon initial upward movement of the pipe.

15. In a device of the character described, a supporting structure having an upward and inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough into and out of pipe engaging position, a carrier for said assembly, a suspension member for the carrier and extending upwardly to a point above said supporting structure, means for lifting the suspension member to move the slip assembly into operative position, and a slip setter below the slip assembly and engaged with the pipe, said setter being adapted to move said assembly upwardly upon initial upward movement of the pipe. 16. In combination, a supporting- structure having an upwardly and inwardly tapering bore adapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable upwardly therethrough from inoperative position into pipe-engaging position, a carrier for said assembly supported from above said assembly but engaging it from beneath, means for shifting said carrier vertically to move the assembly into pipeengaging position, said means embodying a memSber applied to the pipe and to the carrier and adapted automatically to move said carrier and thereby the assembly upwardly upon initial upward movement of the pipe; a snubbing yoke mounted for vertical reciprocation above the supporting structure and having a bore adapted Sto take the pipe, and releasable pipe-gripping elements carried by the yoke.

17. In combination, a supporting structure having an upward and inwardly tapering bore Sadapted to take a vertically extending pipe, a wedge slip assembly within the bore and movable vertically therethrough into and out of pipeengaging position, a carrier for said assembly supported from above said assembly but engaging it from beneath, and means applied to said pipe and to said carrier and operable upon initial upward movement of the pipe to elevate said carrier and thereby move said assembly intc pipe-engaging position.

18. In a device of the character, described, a supporting structure having a bore adapted to take vertically extending pipe therethrough, said bore having a portion tapering upwardly and outwardly and another portion tapering downwardly and outwardly, a pair of wedge-slip assemblies complementary to and entered, one each, in said bore-portions, said assemblies being independently movable vertically through their respective bore-portions in opposite directions from inoperative position into pipe engaging positions, and a slip-setter applied to one of said assemblies and adapted to be applied to the pipe, said setter being operable upon initial movement of the pipe in one direction to move the associated assembly into pipe engaging position without effectively moving the other assembly.

19. In a device of the character described,. a supporting structure having a bore adapted to take vertically extending pipe therethrough, said bore having a portion tapering upwardly and cutwardly and another portion tapering downwardly and outwardly, a pair of wedge-slip assemblies complementary to and entered, one each, in said bore portions, said assemblies being independently movable vertically through their respective bore-portions in opposite directions from Inoperative positions into pipe-engaging positions, and a slip-setter applied to one of said assemblies and adapted to be applied to the pipe, said setter being operable upon initial movement of the pipe in one direction to move the associated assembly into pipe engaging position while the other assembly remains in pipeengaging position.

20. In a device of the character described, a supporting structure having a bore adapted to take vertically extending pipe therethrough, said bore having a portion tapering upwardly and outwardly and another portion tapering downwardly and outwardly, a pair of wedge-slip as- 80 semblies complementary to and entered, one each, in said bore-portions, said assemblies being independently movable vertically thrqugh their respective bore-portions in opposite directions from inoperative positions into pipe-engaging positions, and a pair of slip setters adapted to be applied to said pipe and applied, one each, directly to said assemblies, one of said setters being operable upon initial movement of the pipe in one direction to move its associated assembly into pipe-engaging position, and the other setter being operable upon initial movement of the pipe in the opposite direction to move its associated assembly into pipe-engaging position.

21. In a device of the character described, a supporting structure having a bore adapted to take vertically extending pipe therethrough, said bore having a portion tapering upwardly and outwardly and another portion tapering downwardly and outwardly, a pair of wedge-slip as- g0 semblies complementary to and entered, one each, in said bore-portions, said assemblies being movable vertically through their respective bore-portions in opposite directions from inoperative positions into pipe-engaging positions, and a pair of independently releasable slip setters adapted to be applied to said pipe and applied, one each, to said assemblies, one of said setters being operable upon initial movement of the pipe in one direction to move its associated assembly into pipe-engaging position, and the other setter being operable upon Initial movement of the pipe in the opposite direction to move its associated assembly into pipe-engaging position. 22. In a device of the character described, a supporting structure having a bore adapted to take vertically extending pipe therethrbugh, said bore having a portion tapering upwardly and outwardly and another portion tapering downwardly and outwardly, a pair of wedge slip assemblies complementary to and entered, one each, in said bore-portions, said assemblies being independently movable vertically through their respective bore-portions in opposite directions from inoperative positions Into pipe-engaging positions, a slip-setter applied to one of said assemblies and adapted to be applied to the pipe, said setter being operable upon initial movement of the pipe in one direction to move the associated assembly into pipe engaging position, and means for moving the other assembly into and out of pipe engaging position without effectively moving said one assembly.

23. In combination, a supporting structure having an upwardly and inwardly tapering bore adapted to take a vertically extending pipe, a wedge-slip assembly within the ,bore and movable upwardly therethrough from inoperative positlon into pipe-engaging position, manually operated means for moving said assembly upwardly, and a slip-setter operatively connected to the assembly and engageable with said pipe; said setter, when engaged with the pipe, being adapted automatically to move said assembly upwardly upon initial upward movement of the pipe without coincident effective movement of said manually operated means.

24. In combination, a supporting structure having an upwardly and Inwardly tapering bore adapted to take a vertically extending pipe, a wedge-slip assembly within the bore and movable upwardly therethrough from inoperative position into pipe-engaging position, manually operated means for moving said assembly upwardly, and a slip-setter positioned below and operatively connected to the assembly and engageable with said pipe; said setter, when engaged with the pipe, being adapted automatically to move said assembly upwardly upon initial upward movement of the pipe without coincident effective movement of said manually operated means.

25. In a device of the character described, a supporting structure having a bore adapted to take vertically extending pipe therethrough, said bore having a portion tapering upwardly and outwardly and another portion tapering downwardly and outwardly, a pair of wedge-slip assemblies complementary to and entered, one each, in said bore-portions, said assemblies being independently movable vertically through their respective bore-portions in opposite directions from inoperative positions into pipe-engaging positions, manually operated means for moving said assemblies vertically, and a slip-setter operatively connected to one of said assemblies and engageable with the pipe, said setter, when engaged with the pipe, being adapted automatically to move said one assembly into pipe-engaging position o5 without coincident effective movement of said manually operated means.

FREDERICK STONE.

ALBERT L. STONE.