Power Slip Unit

This invention relates to improved power slip mechanisms for facilitating the handling of well pipe.

During the drilling of a well, there are various situations in which it becomes desirable to temporarily support the weight of the drill string by a set of tapered slips received within a tapered slip bowl while an upper joint or stand of pipe, or a kelly, is being connected to or disconnected from the string. To speed the setting and release of such slips, there have been devised power slip units in which a number of slips have been power actuable upwardly and downwardly relative to a coacting slip bowl, to move the slips into and out of engagement with the tapering camming surface of the bowl. In some instances, the slip assembly has also been mounted to swing laterally to a location at a side of the well pipe when not in use. As examples, certain of the prior power slip arrangements are shown in U.S. Pat. Nos. 2,939,683, 3,210,821, 3,270,389 and 3,457,605.

A major purpose of the present invention is to provide an improved power slip device which is considerably simpler than the prior power slips of which I am aware, and yet which in spite of that simplicity is capable of being set and released more efficiently than prior devices with respect to the expenditure of rig time, so that the overall operation of making or breaking a particular threaded connection can be performed more rapidly. Further, the entire slip assembly is more easily shiftable to a retracted position at the side of the pipe to completely avoid any interference with other equipment on the well when the slips are not in use.

These advantages are achieved in large part by formation of the apparatus in a manner enabling the slips to be moved vertically into and out of the slip bowl by movement of the well pipe itself, through actuation of the pipe raising and lowering mechanism of the rig, and without the necessity for provision of an additional power unit or units in the slip device for raising and lowering the slips. Preferably, the movements of the well pipe which are relied on for setting and releasing the slips are movements which are normally made by the pipe in the conventional processes of making and breaking threaded connections, regardless of what type of slip mechanism is employed. Thus, rig time is saved by utilizing more efficiently time already required for shifting the pipe during a connecting or disconnecting operation, and eliminating the necessity for use of a different interval of time to actuate the slips upwardly or downwardly by other means.

Structurally, the apparatus of the invention includes a slip assembly which is adapted to be clamped about and inwardly against a well pipe in a relation locking the slips at a fixed location on the pipe and against relative axial movement. Powered means are provided for urging the slips to this clamping condition. After the slips have been clamped on the pipe in this way, the pipe may be lowered sufficiently to bring the carried slips into engagement with the tapering cam surface of a slip bowl, so that the pipe may thereafter be supported from the bowl by the slips. Similarly, after a particular connecting or disconnecting operation has been completed, the pipe string can be pulled upwardly a short distance relative to the rotary table and slip bowl, to thus move the slips upwardly out of the bowl. The slips may then be released from their clamped condition, and if desired can be swung laterally to a retracted position at a side of the pipe until the next successive connecting or disconnecting operation is to be performed.

The slips per se may be articulately interconnected as a slip assembly forming at one side a throat through which the well pipe may pass during movement of the assembly between active and retracted positions, with that throat being at least partially closeable when the slips are in their pipe clamping conditions. The power unit for actuating the slips to their clamping condition may be a piston and cylinder mechanism, connected to a pair of opposite side slips of the assembly to actuate them toward and away from one another.

Certain additional features of the invention relate to an automatic control or sequencing system for controlling movement of the slips between their clamping and released conditions. Desirably, once an operator has commenced movement of the slip assembly inwardly toward the well pipe from a retracted position offset to a side of the pipe, the slip assembly, without further manual control, automatically continues its inward advancement to a position about the pipe, and then closes to clamping condition to grip the pipe.

The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a well tool which includes a power slip constructed in accordance with the present invention;

FIG. 2 is an enlarged side view of the power slip of FIG. 1, taken on line 2--2 of FIG. 1;

FIG. 3 is a plan view of the power slip taken on line 3--3 of FIG. 2;

FIG. 4 is an enlarged horizontal section taken on line 4--4 of FIG. 2;

FIG. 5, 6 and 7 are fragmentary vertical sections taken on lines 5--5, 6--6 and 7--7 respectively of FIG. 4;

FIG. 8 is a view similar to FIG. 4, but showing the slip assembly in open condition;

FIG. 9 is a side view of the slip assembly, taken on line 9--9 of FIG. 8;

FIG. 10 is a section taken on line 10--10 of FIG. 9;

FIG. 11 is a fragmentary plan view, taken primarily on the plane of line 11--11 of FIG. 2, but showing the slips in open condition and deflected laterally for gripping a pipe which is offset to one side of the slip bowl; and

FIG. 12 is a schematic representation of the hydraulic system of the slip.

The well tool which is designated generally by the number 10 in FIG. 1 is utilized on a well rig for making and breaking threaded connections in a vertical drill string or other well pipe 11 which extends downwardly through the usual rotary table 12 into the well. Tool 10 includes an upstanding support 13 mounted to the floor 14 of the rig at a location offset to one side of the well pipe 11 and its vertical axis 15. A power slip unit 16 formed in accordance with the present invention is movably mounted to support 13. Above the power slip unit, support 13 carries a pipe turning assembly 17, which includes a spinner 18 for turning an upper joint 19 of the pipe relatively rapidly in making and breaking a connection, and a torque wrench 20 beneath the spinner having upper and lower gripping assemblies 21 and 22 for gripping two successive joints of the pipe and turning them with substantial torque during the final portion of the makeup operation or the initial part of an unthreading operation. The assembly 17 is mounted by an arm 23 to swing laterally between an active position about the pipe and a retracted position offset to a side of the pipe. To permit such swinging movement, the spinner and torque wrench have appropriate openings or gates at one side to pass the drill pipe laterally. The present application is concerned primarily with the structure and method of operation of the power slip unit 16.

The support 13 may include a base plate 24 which is welded, bolted or otherwise rigidly secured to the rig floor, and which carries two similar spaced vertical upwardly projecting track members 25 and 26, which for their entire vertical height from the level of base plate 24 to their upper extremities 27 (FIG. 2) have the H-shaped horizontal cross-section illustrated in FIG. 3. These track members 25 and 26 may be secured together and reinforced at their rear sides by a vertical plate 28 appropriately welded or otherwise secured to the track members, and by spaced parallel vertical rear supporting plates 29 and 30 secured to plate 28.

A carriage 31 is mounted between tracks 25 and 26 for movement upwardly and downwardly along a vertical exis 32 parallel to the main vertical axis 15 of the well. This carriage 31 may include a front vertical plate 33 secured to a pair of parallel opposite side plates 34 and 35 which rotatably carry vertically spaced pairs of rollers 36 turning about horizontal axes 37 and 37'. These rollers are received within vertical guideways 38 and 39 formed at the inner sides of track members 25 and 26, and engage the sidewalls of those guideways in a manner guiding carriage 31 for only the desired vertical movement along axis 32.

The carriage 31 and the remainder of the power slip assembly carried thereby are yieldingly urged upwardly by a counterweight 40, which may be rectangular as shown and be guided for upward and downward movement along a vertical axis 41 parallel to axis 32. This counterweight is slidably received and guided between wall 28 and two vertical angle irons 42 and 43 (FIG. 3) carried by members 29 and 30, with the counterweight being confined laterally by forward portions of the plates 29 and 30. Flexible cables 44 suspend the counterweight, and extend upwardly therefrom and about two pulleys 45 mounted rotatably by a shaft 46 supported by brackets 47 carried by the upper edge of plate 28. These pulleys 45 turn about a horizontal axis 48. After passing about the pulleys, cables 44 extend downwardly to points of connection at 49 (FIG. 2) to the upper edge of carriage 31. The mass of counterweight 40 is sufficient to normally maintain carriage 31 and the entire power slip assembly 16 carried thereby in their upper broken line positions of FIG. 2, in which the entire slip unit is located above the level of the rig floor and is therefore free to swing laterally into and out of engagement with the well pipe.

The slip assembly 16 includes an elongated horizontally extending arm 50 which may be hollow and fabricated of sheet metal top, bottom and side walls cut to give the arm the external shape illustrated in the figures, and welded together along their meeting edges. At one end, this arm is mounted to carriage 31 for horizontal swinging movement between the broken line retracted and full line active positions of FIG. 3, and about a vertical axis 51, relative to the carriage. This pivotal mounting may be attained by providing carriage 31 with three similar vertically spaced horizontal mounting plates 52 (FIG. 2) secured to and projecting forwardly from wall 33 of the carriage, and containing openings through which a vertical pivot pin 53 extends, with the pin also passing through circular openings, in portions 54 of the top and bottom walls 55 and 56 of arm 50. A hydraulically actuated piston and cylinder mechanism 57 swings the arm 50 between its two FIG. 3 positions, and may have its cylinder pivoted to plates 52 at 58, and its piston rod pivoted to arm 50 at 59.

At its free end, arm 50 carries a slip assembly 60 preferably including a first central slip 61 and two opposite side slips 62 and 63 pivoted to central slip 61 for relative swinging movement about two parallel vertical axes 64 and 65 between the closed pipe gripping positions of FIGS. 3 and 4 and the open positions of FIGS. 8 and 11. These pivotal connections between the slips are provided by two elongated parallel vertical threaded screws 66 and 67 (FIGS. 8 and 9), each of which extends through a pair of tubular hinge lugs 68 on the center slip 61 and an intermediate tubular hinge lug 69 on one of the side slips 62 or 63, with the hinge screws 66 and 67 being retained by heads 70 at their lower ends and nuts 71 at their upper ends.

The bodies of the three slips are of conventional downwardly tapering wedge-shaped configuration, as shown, to coact with a correspondingly downwardly tapering conical inner surface 72 of a slip bowl 73 supported by a master bushing 74 within the rotary table 12. At their radially inner sides, the three slips carry gripping dies 75 of any conventional type having gripping edges 76 which in the closed FIG. 4 condition of the slips follow essentially the curvature of the outer cylindrical surface of the well pipe, and tightly grip the pipe in a manner preventing relative vertical movement between the pipe and slips. At their radially outer sides, the slips have downwardly conically tapering outer cam surfaces 77 which follow the curvature of and are essentially continuously engageable with slip bowl surface 72 in the closed condition of the slips, to cam the slips inwardly against the pipe in response to exertion of downward force, and thereby support the weight of the pipe from the rotary table in the usual manner.

In order to allow the three slips to turn together through a limited range of movement and to a position such as that shown in FIG. 11 relative to the mounting arm 50, all three of the slips are carried by a mounting part 77' which is connected to arm 50 for pivotal movement relative to the arm about a vertical axis 78. The pivotal connection between these parts includes an externally cylindrical pivot pin 79 (FIG. 5) having a head 80 which is welded to part 77', with the cylindrical shank of the pin projecting upwardly through that part and upwardly thereabove and being journalled rotatably within circular openings 81 and 82 in top and bottom walls 55 and 56 of arm 50. A nut 83 threadedly connected onto the upper end of pivot pin 79 may act downwardly against top wall 55 of arm 50 through a washer 84 to support the pin and slip assembly from the arm. A coil spring 85 disposed about pin 79 at a location within the hollow arm 50 has two outwardly turned arms 86 and 87 (FIG. 11) at its opposite ends which are normally in engagement with opposite sides of an upstanding pin 88 carried by arm 50, to yieldingly hold part 77' and the carried slips in the central position illustrated in FIG. 4 and 8. The pivot pin 79 carries a ring 89 (FIG. 9), which is secured against rotation relative to pin 79 by a set screw or lock pin 90 extending into a slot or opening 91 in pin 79. The ring 89 rigidly carries an upwardly projecting pin or post 92 which is normally received in alignment with and adjacent the pin 88, and which upon turning movement of part 77' about axis 78 relative to arm 50 acts against one or the other of the spring ends 86 or 87 to move that spring end circularly about axis 78 relative to the other end of the spring. For example, in FIG. 11, pin 92 has moved the spring end 86 in a counterclockwise direction relative to the spring end 87, so that the spring yieldingly resists the turning movement of part 77' from its FIG. 4 centered position to its FIG. 11 position, at which setting the turning movement of part 77' and the carried slips is limited by engagement of a shoulder 93 on a part 94 carried by member 77' with a side surface 95 of arm 50. Similarly, swinging movement of part 77' in the opposite direction is limited by engagement of a shoulder 96 on part 94 with the side surface 95 or arm 50.

The center slip 61 is held in fixed position relative to and substantially directly beneath the carrier part 77' by extension of the previously discussed slip hinge screws 66 and 67 through the hinge lugs 68 at the opposite sides of slip 61 and also through vertical openings 97 (FIG. 9) in part 77'.

The two side slips 62 and 63 are power actuated between their open and closed conditions of FIGS. 8 and 4 respectively, and are urged in a closing direction beyond the FIG. 4 condition to tightly grip and clamp inwardly against the pipe, by a fluid actuated piston and cylinder mechanism 98, whose cylinder 99 is pivotally connected at 111 to a clamping arm 100 secured to slip 63, and whose piston rod 101 projecting from piston 102 is pivotally connected at 112 to a clamping arm 103 secured to slip 62. As seen best in FIGS. 7 and 9, the clamping arm 103 may be formed sectionally of a lower essentially horizontal plate 104, two upper plates 105 and 106, and an intermediate block 107, all rigidly secured together in appropriate manner as by a number of screws 114 extending downwardly through these various parts, with parts 104, 106, and 107 containing aligned apertures 108 through which hinge pin 66 extends, and with parts 104, 106 and 107 being confined vertically between part 77' and an upwardly facing surface 109 formed on a flange 110 projecting laterally from and carried by slip 62. The parts 104 and 107 have shoulders 115 which bear against a side surface 116 formed on the top portion of slip 62 in a relation effectively transmitting clamping force from arm 103 to that slip. In addition, arm 103 may be suitably rigidly connected to slip 62 to transmit swinging movement in both directions from the arm to the slip, as by welding these parts together or otherwise interconnecting them.

The pivotal connection 112 between piston rod 101 and clamping arm 103 may be formed by providing the end of the rod with a tubular vertically extending portion 117 received and confined between plates 104 and 105, and disposed about a vertical pivot pin 118 which is retained at its upper and lower ends within openings 119 in plates 104 and 105. The pivotal axis 120 of this connection between the piston rod and arm 103 extends vertically and parallel to the pipe axis.

The other clamping arm 100 is formed sectionally in the same manner as arm 103, except that arm 100 is a mirror image of arm 103 to properly engage and be connected to the oppositely directed side slip 63. The pivotal connection 111 between cylinder 99 and arm 100 may be formed by providing the cylinder with upper and lower trunion shafts 121 (FIG. 6) journaled within openings formed in upper and lower plates 105' and 104' of arm 100 corresponding to upper and lower plates 105 and 104 of arm 103.

Referring to FIG. 12, the hydraulic system for controlling actuation of the slip unit 16 includes a three position manually actuated valve 120' which receives pressure fluid from a main hydraulic supply pump 121' and controls the delivery of pilot presures to a second three position hydraulic valve 122. Pump 121' delivers pressurized fluid to valve 122 through a check valve 123, with the return line 124 from valve 122 leading to an accumulation tank 125 from which the pump takes suction.

The diagrammatically represented main valve 122 is yieldingly urged by springs 126 to the closed position in which the valve is shown in FIG. 12. In that position, the pressurized fluid from pump 121' is directed by valve 122 into return line 124, without delivery of any of the pressurized fluid to either of the lines 128 or 129 at the discharge side of valve 122. When valve 120' is actuated from its neutral or closed condition to a second of its settings, the pilot pressures thus delivered to valve 122 actuate that valve downwardly as viewed in FIG. 12 so that the upper section of the valve diagrammatically represented at 130 places line 127 in communication with line 129, and places line 124 in communication with line 128. Similarly, in an opposite or third position of valve 120', the pilot pressures actuate the body of valve 122 upwardly so that the lower section 131 of the valve places line 127 in communication with line 128, and places line 124 in communication with line 129.

Line 128 is connected by a line 132 to the rod end of clamping cylinder 99, and is connected through a valve 133 to the rod end of piston and cylinder mechanism 57 which swings the slip carrying arm between active and retracted positions. This valve 133 is adapted to automatically respond to movement of the slip carrying mechanism to its uppermost position in which the slips are high enough to be located entirely above the level of the rotary table and slip bowl structure, so that the slip mechanism can be safely swung horizontally between its active and inactive positions. For example, the valve 133 may typically be positioned as shown in FIG. 2, to be engageable by a portion of carriage 33 (such as one of the plates 52) when the carriage reaches its uppermost position. As represented diagrammatically in FIG. 12, the movable part of valve 133 may be spring urged downwardly to a position in which an upper section 134 of that valve closes off communication between two lines 135 and 136 communicating with valve 122 and mechanism 57 respectively. When the valve is actuated upwardly by arrival of the slips in their uppermost position, a lower section 137 of valve 133 then becomes effective to place lines 135 and 136 in communication.

Pressure fluid for actuating the clamping cylinder mechanism 98 is delivered to that mechanism from line 129 through another automatic valve 138, which as diagrammatically represented is spring urged upwardly to a position in which its lower section 139 closes off communication between two lines 140 and 141. Upon a predetermined increase in pressure in line 140, communicated through a line 142, the valve is actuated downwardly to a position in which its upper section 143 places lines 140 and 141 in communication. A check valve 144 allows flow from line 141 to line 140 upon unclamping actuation of piston and cylinder mechanism 98.

To describe a cycle of use of the power slip, assume that arm 50 and the carried slip assembly are initially in their retracted or inactive positions in which the slips are offset to a side of the well (broken lines in FIG. 3). When it is desired to actuate the slips to grip and support a well pipe, the operator actuates valve 120' from its neutral position to a second position, to correspondingly move pilot controlled valve 122 to a position in which its upper section 130 delivers pressurized fluid to line 129, and through that line to the swing cylinder 57, thereby causing that cylinder to commence swinging movement of arm 50 and the carried slips from their broken line positions of FIG. 3 inwardly toward the well pipe and the full line positions of FIG. 3. Pressure is simultaneously delivered through line 140 to valve 138, but that pressure is insufficient to actuate the valve downwardly against its adjusted spring resistance far enough to pass the pressurized fluid to cylinder 98. When the slips reach a position in which the center one of the slips 61 engage the pipe, this engagement prevents further movement of slip 61 and arm 50, and thereby causes an increase in pressure in swing cylinder 57, which increase in pressure is communicated through lines 140 and 142 to the upper end of valve 138, and actuates that valve downwardly to a position in which its upper section 143 delivers the pressure fluid from line 140 to the lower end of clamping cylinder 98. This pressure causes the clamping cylinder mechanism 98 to force rod 101 of that mechanism outwardly relative to cylinder 99, and thereby clamp slips 62 and 63 toward one another and against the pipe, to the clamped condition of FIG. 4, in which the three slips tightly grip the pipe with a force frictionally locking the slips against upward or downward movement relative to the pipe. The operator then actuates the raising and lowering mechanism of the rig to lower the well pipe far enough to bring the three slips into engagement with slip bowl surface 72, so that the weight of the pipe can thereafter be supported from the slips in conventional manner. When it is desired to release the slips, the rig mechanism is actuated to raise the well pipe and attached slips upwardly from the slip bowl, and valves 120' and 122 are actuated to reversed positions in which pressure fluid is supplied to the rod ends of clamping cylinder 98 and swing cylinder 57, to release the clamping engagement of the slips with the pipe, and swing the slips and their carrying arm laterally to their retracted positions. Counterweight 40 assures full return of the slips to their uppermost positions as soon as the clamping engagement with the pipe is released, and valve 133 prevents delivery of the actuating pressure to swing cylinder 57 until the slips are in their uppermost positions and high enough to move laterally without contacting any portion of the rotary table or its carried parts. During the slip unclamping actuation of piston and cylinder mechanism 98, the pressure fluid is bypassed around valve 138 through check valve 144.

If during the swinging movement of the slips from their retracted to their active positions, the well pipe is off center with respect to the axis of the well and the slip bowl, as represented in FIG. 11, one of the diverging cam surfaces 145 of the two clamping slips 62 and 63 engages the pipe in a relation turning the entire slip assembly about axis 78 relative to part 77 and arm 50 far enough to enable the pipe to enter the slip assembly between the surfaces 145 of the slips. Because of the manner in which clamping cylinder 98 is connected to slips 62 and 63, it also can swing with these slips about axis 78, and can effectively perform its clamping action even though the well pipe is offset from the main well axis.

While a certain specific embodiment of the present invention has been disclosed as typical, the invention is of course not limited to this particular form, but rather is applicable broadly to all such variations as fall within the scope of the appended claims.