GB1592943A

GB1592943A - Tongs arrangement for making and breaking joints between lengths of drill pipe

Info

Publication number: GB1592943A
Application number: GB140080A
Authority: GB
Original assignee: BJ Hughes Inc
Current assignee: BJ Hughes Inc
Priority date: 1977-03-15
Filing date: 1978-02-23
Publication date: 1981-07-15
Also published as: GB1592942A

Description

PATENT SPECIFICATION

( 21) ( 62) ( 31) ( 33) ( 44) ( 51) ( 52) ( 11) Application No 1400/80 ( 22) Filed 23 Feb 1978 Divided out of No 1 592 941 Convention Application No.

777 724 ( 32) Filed 15 March 1977 in United States of America (US) Complete Specification published 15 July 1981

INT CL 3 G 05 B 11/01 Index at acceptance G 3 N 287 CA 2 ( 54) A TONGS ARRANGEMENT FOR MAKING AND BREAKING JOINTS BETWEEN LENGTHS OF DRILL PIPE ( 71) We, B J HUGHES, INC, a Corporation organised and existing under the laws of the State of Delaware, United States of America, of 6505 Paramount Boulevard, Long Beach, California, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:This invention relates to a tongs arrangement for making and breaking joints between length of drill pipe.

Tongs are well known for making and breaking joints between pipe stands and the drill string (see for example, United States Patent 3,881,375).

The tongs are, as is known in the art, a hydraulically powered arrangement capable of making and breaking joints in a drill string It is an object of the present invention to provide an electronic network controlling the operations of the tongs, and to interconnect that control network with a programmed general purpose digital computer so as to repeatedly and efficiently operate the tongs to perform its function.

Accordingly, the present invention provides a tongs arrangement for making and breaking a joint between lengths of drill pipe comprising: tongs lifting and lowering means; means for controlling a lifting speed; a backup tong; a power driven tong; means for generating an electrical signal to lift the backup and the power driven tong at a predetermined speed to a predetermined elevation; means for generating a first electrical feedback signal representative of the tongs being disposed at said predetermined elevation; means responsive to said first feedback signal for generating an electrical signal to close and lock a backup tong when it is lifted to a predetermined elevation; means for generating a second electrical feedback signal representative of the closure and locking of said backup tong; and, means responsive to said second feedback signal for generating an electrical signal to drive a power driven tong when a backup tong is closed and locked.

In order that the invention may be readily understood an embodiment thereof will now be described by way of example, with reference to the accompanying drawings, in 55 which:

FIGURE 1 is a generalized block diagram illustrating the interactions between derrick structure and control systems therefore and a digital computer in an automated oil 60 drilling rig provided with a tongs arrangement embodying this invention; FIGURE 2 is an illustration of the structural elements included on an oil derrick, drilling rig, or and the various structural sys 65 tems disposed thereon; FIGURE 3 is a highly stylized pictorial representation, similar to Figure 2, of a power tong assembly illustrating conventional tong elements and elements associ 70 ated therewith according to this invention; FIGURE 4 is a detailed schematic diagram of an electro-hydraulic interface embodying the teachings of this invention and disposed in a power tong assembly in 75 accordance with Figure 3; FIGURE 5 is a block diagram indicating the interconnection between a programmable general purpose digital computer and the tong control assembly according to this 80 invention; FIGURE 6 is a detailed schematic diagram of an automatic tong control system embodying the teachings of this invention; FIGURES 7 A and 7 B are timing diag 85 rams for the automatic tongs control system shown in Figure 6 in the make-up and break-out cycles, respectively; FIGURES 8 A and 8 B, are, respectively detailed elevational and top views of a joint 90 sensor for a power tongs assembly in accordance with the teachings of this invention; and, FIGURE 9 is a definitional diagram of two commonly used drill pipe configurations 95 illustrating the structures thereof to assist in the description of the joint sensor shown in

Figures 8 A and 8 B. Referring first to Figure 1, a generalized block diagram of a computer controlled oil 100 1 592 943 ( 19) -E H 1 592 943 drilling rig, or derrick which is described in detail in our copending Application No.

7365/78 (Serial No 1592941) is illustrated.

Generally speaking, the derrick includes three broad structural systems each performing a particular set of functions relating to thc drilling of an oil well, and a control system related to each structural system to control the physical actions performed thereby.

The derrick includes a drawworks structural system 22 having a drawworks control systeni 21 associated therewith The drawworks system generally provide the hoisting (or lifting) and lowering functions associated with the generation of a well bore Command signals output from the drawworks control system 21 are input to the structural system 22, as diagrammatically illustrated by a line 23, and initiate or cease the physical actions of elements within the structural system 22 Feedback signals representative of various physical parameters associated with each of the structural elements within the drawworks structural system 22 are input to the control system 21, as illustrated by a line 24 The derrick also includes a power tongs structural system 28 and a tong control system 29 associated therewith The tong systems generally provide the make-up or break-out of individual pipe stands into or out of a drill string Command signals initiating or ceasing the physical actions of structural elements of the tongs structural system 28 are input thereto from the tongs control system as 29, as illustrated by a line 30.

Feedback signals representative of various physical parameters associated with each of the structural elements within the tongs structural system 28 are input to the tongs control system 29 as illustrated by a line 31.

Also provided is a racker structural system 34 which, in general, provides the structure necessary for carrying individual pipe stands from a storage location to a location along the vertical axis of the derrick for make-up or from the location along the vertical axis of the derrick to the storage location during break-out The storage location is known in the art as the "set back" A racker control system 35 is provided, with control signals being output therefrom to the structural system 34, as illustrated by a line 36 Feedback signals from the structural system 34 are input to the racker control system 35, as illustrated by a line 37.

A general purpose programmable digital computer 40 is interfaced with each of the above-mentioned control systems, as illustrated diagrammatically by a line 41 (to the drawworks control system 21), a line 42 (to the power tong control system 29) and a line 43 (to the racker control system 35) Each of the control systems feed back various signals to the computer 40, as illustrated by the lines 44, 45, and 46, from the drawworks control system 21, tongs control system 29, and racker control system 35, respectively Further, the computer 40 70 receives direct data input of physical parameters, as illustrated as by a line 47.

The computer, in accordance with the programmed instructions, sequentially initiates the operations of various of the struc 75 tural systems to perform various physical functions within the derrick To economize operating time and maximize efficiency, control of the systems may be on a time shared basis, as with control of the draw 80 works and racker systems Any interactions between the systems, as between drawworks and tongs, are through the computer 40.

Referring to Figure 2, shown is an illustra 85 tion of the oil drilling rig, or derrick incorporating the basic rig features and having thereon the structural elements which are included in the structural systems outlined in connection with Figure 1 These struc 90 tural systems are in cooperative association with their associated control systems to initiate and cease the operation of the physical functions performed by the structural systems The derrick is illustrated in simp 95 lified form, with various structural supports, sway bars, and other similar members being omitted for clarity.

The basic derrick structure includes corner posts 51 and 52 extending substan 100 tially upwardly from suitable base members.

The base members are supported on a drilling floor 53, the drilling floor 53 being mounted on the surface of the earth, on an off-shore drilling platform or on a drill ship 105 A rotary table is provided in the floor 53 of the derrick and provides the rotational energy whereby a drill string, comprised of end-to-end connected drill pipe stands, may be advanced toward a hydrocarbon produc 110 ing formation Slips 55 are shown on the floor 53 When engaged, the slips 55 support the full weight of the drill string depending therebeneath In Figure 2, the upper end of the drill string, or more pre 115 cisely, the upper end of the uppermost pipe stand connected within the drill string, is shown as protruding above the slips 55.

Each upper end of the pipe stand has a distended joint 56 used in connection with the 120 tong operation The programmable general purpose digital computer 40 may be conveniently housed in a structure 57 on the floor 53.

The axis of the bore being generated 125 beneath the floor 53 of the derrick extends centrally and axially through the derrick A racker structural system, generally indicated by the reference numeral 34, carries individual pipe stands between a storage loca 130 1 592 943 tion, or "set back", disposed at the side of the derrick and a location along the vertical axis thereof It is along the vertical axis of the derrick that the drill string is retracted from or lowered into the bore being generated The racker structure 34 includes a lifting head 58, an upper arm 59 with a latch thereon, carriages 60 and 61 for the head 58 and for the arm 59, respectively, and a racker board 62 for receiving and supporting individual pipe stands.

The corner posts 51 and 52 are interconnected with and supported by transverse supports at various elevations along the derrick The derrick is capped by a water table which supports the usual crown block 66.

Suspended from the crown block 66 by a cable arrangement 67, or reaving, are elements of the drawworks structural system, including a traveling block 68 The traveling block 68 supports a hook structure 70 by interengaged bales 71 Elevator links are suspended from an ears 73 on the hook structure 70 The links 72 have an elevator 75 swingably attached at the lower ends thereof The elevator 75 is offset below the traveling block 68 by a predetermined distance h The elevator 75 includes a gripping arrangement to grasp or release the distended ends 56 of a pipe stand.

A block retractor arrangement 78 is connected to the traveling block 68 and serves to retract the traveling block (with depending elevator 75) away from the vertical axis of the derrick along which it usually depends The retractor 78 includes a carriage 79 which is rectilinearly moveable through a wheeled arrangement along a substantially vertically extending retractor guide track 80 A block position and speed transducer (B P S T) 83 is mounted on the retractor carriage 79 and produces output feedback signals representative of the actual physical position of the traveling block 68 along the track 80 These feedback signals, as will be seen, are provided both to the drawworks control system 21 (Figure 1) and to the computer 40 The block position transducer 83 also provides a feedback signal representative of the velocity at which the traveling block 68 is moving along the track 80 Of course, it may be readily appreciated that since the elevator 75 is vertically offset by the distance h from the traveling block 68, the position of the traveling block 68 along the track 80 also indicates the position of the elevator 75 with respect thereto, and vice versa And, since the traveling block 68 and the elevator 75 are generally extended to move along the vertical axis of the derrick, the position (elevation), and velocity of the traveling block 68 with respect to the vertical axis of the derrick 20 may be accurately monitored by the block position and speed transducer 83.

For a purpose more fully disclosed herein, upper and lower limit switches are provided on the carriage 79 An upper target 86 and a lower target 87 are provided at determined locations on the retractor guide track 80 70 As is the usual practice in the art, the cable arrangement 67 which supports the traveling block 68 and structures (including the elevator 75) depending therefrom are reaved about the block 66 One end 88 of 75 the cable arrangement 67, known as the "dead line" in the art, is anchored to the derrick as illustrated at 89 The second end of the cable arrangement 67, known as the "fast line" is connected to other ele 80 ments included in the drawworks structural system More particularly, the fast line 90 is attached to a spool or drum 91 of the drawworks The drum 91 is driven by an electric motor 92 of any suitable type as diagram 85 matically illustrated in Figure 2 For example, a motor manufactured by the Electromotive Division of General Motors, sold under Model No D 79 GB and rated at 800 horse-power for drilling is a typical motor 90 for a drawworks structural system Determination of a motor lies well within the skill of the art The motor 92 is provided with a motor drive 93, such as a THYRIG manufactured by Baylor Company, although any 95 other motor drive arrangement may be used The motor 92 may be wound in any predetermined configuration to meet the needs of a particular rig It is noted, however, that the motor 92 imparts the energy 100 whereby the traveling block 68 and the structures depending therefrom may be moved with respect to the vertical axis of the derrick 20 from a first predetermined to a second predetermined elevation Therefore, 105 control of the motor drive 93, and in turn, of the motor 92, effectively controls the velocity and acceleration of the traveling block 68 as it is lifted from a first to a second elevation The drawworks includes a suitable 110 clutch and gear arrangement therein.

A drum tachometer 94 is physically located in adjacency to the spool 91 The output of the drum tachometer 94 is a feedback signal to the drawworks control system 115 21 representative of the velocity of the spool 91 which signal is directly proportional to the velocity of the traveling block 68 and depending structures Within the dead line 88 is provided a transducer 95 known as the 120 dead line force sensor (D L F S) The transducer 95 provides a feedback signal to the drawworks control system 21 related to the physical loading of the structure supported by the cable arrangement 67 Of 125 course, the cable arrangement 67 at all times supports the traveling block 68 and its depending structures The unloaded, static weight of these structures defines a "tare" weight of the structure supported by the 130 1 592 943 cable 74 arrangement 67 When the elevator 75 acquires a load, the D L F S 95 appropriately reacts Similarly when the elevator load is properly relinquished, the sensor 94 responds accordingly Yet further.

during movement of a loaded traveling block 68, frictional or other forces may alter the load carried by the elevator 75 The D.L F S 95 therefore provides an accurate feedback signal as to the instantaneous loading on the elevator 75 of the drawworks structure As is generally the case with the other transducers, other convenient physical locations therefor may be used to measure the desired parameters In addition, any appropriate means for measuring the desired parameters may also be utilized, as is appreciated by those skilled in the art.

Also included within the drawworks structural system is a brake The drawworks brake includes a primary brake the function of which is to control the velocity and deceleration of the drawworks traveling block (when unloaded) and to stop the motion thereof An auxiliary brake is also provided within the drawworks structural system to substantially absorb the potential energy associated with the lowering of a loaded traveling block In the particular embodiment of the invention shown in Figure 2, the primary brake is a drum brake 96, manually operable by a pivotable lever 97 A spring 98 biases the drum brake 96 into its fully asserted position The lever 97 may be connected to a brake actuator assembly generally indicated by the numeral 99 The brake actuator assembly 99 includes a cylinder having a piston 101 therein The piston 101 is couplesi to the lever 97 The brake actuator 9 i Y also includes an electro-topneumatic interface such that the cylinder may be coupled to a suitable supply of pressurized air or any other fluid such that introduction of the fluid into the cylinder

100 moves the piston 101 therein which moves the lever 97 so as to modulate the force on the brake.

As mentioned above, it is known to those skilled in the art that the secondary brake is provided to absorb the energy when the loaded traveling block is moved downwardly from an upper to a lower elevation.

A manually controlled hydromatic brake may be used as an auxiliary brake However, an electric brake, such as an ELMAGCO brake sold by Baylor Company could typically be used The brake control subsystem of the drawworks control system 21 can be readily interfaced with an auxiliary brake by those having skill in the art so as to provide the desired velocity and deceleration control Final position is ultimately controlled by the drum brake 96.

It is important to note that whatever auxiliary brake configuration and actuator therefor is utilized, the drawworks structure includes a brake which is controlled by the drawworks control system 21 so that the desired velocity acceleration of the traveling block 68 is maintained as it moves from an 70 upper to a lower final position Also, the brake is operable to set and hold a lifted or hoisted load in the upper position If the operator deems it necessary to halt the movement of the physical structures associ 75 ated with the drawworks, the operator may at any time override the electrical signal output from the drawworks control system by actuating a switch 103 mounted on the lever 97 The operator may also, at anytime, 80 override the electrical signal output from the drawworks control system 21 by depressing a push-button switch located in the control panel 104 The spring 98 may be manually overridden to release the brake 85 The racker structure 34 is operable to carry a pipe stand from the vertical centerline of the derrick to the set back In a make-up cycle, the pipe stand to be added is stabbed into the already emplaced and con 90 nected stands which comprise the drill string When joined to the drill string, the racker structure 34 relinquishes the load to the drawworks, which lowers the string into position In a breakout cycle, the drawworks 95 structure 22 withdraws the drill string, and, as each pipe stand is disconnected from the string, the racker structure 34 accepts the load from the drawworks and moves the pipe stand to a storage location 100 The actual connection and disconnection of pipe stands from the drill string is accomplished by the power tongs structure 28 under the control of the tongs control system 29 Very briefly, the tongs includes a 105 backup, which holds the lower pipe element defining the joint, while a second element of the tongs the power driven tong connects or disconnects a pipe stand to the upper pipe element The tongs also includes a lift to 110 move the associated back jaws structure at a predetermined speed to a predetermined operating elevation with respect to the vertical axis of the derrick The backup and the jaws usually circumferentially surround the 115 drill string as it advances in the bore Put another way, the vertical axis of the derrick usually extends through the openings in the backup and jaws of the tongs to facilitate gripping and disconnection or connection 120 operations Until needed, the tongs are stored in a lowermost storage position.

When it is convenient to do so, the tongs are lifted to a standby position which is proximate to the elevation at which the distended 125 joint 56 of the drill string is raised by the drawworks To sense the distended joint 56, a joint sensor 1025 (which is described and claimed in our co-pending Application No.

8001399, Serial No 1592942) is provided 130 1 592 943 to contact the exterior of the drill string as the tongs are moved from the standby to the operating position The movement from the standby to the operating position is at a slower speed, of course, than the speed at which the tongs are moved from the storage position to standby position.

The particular joint sensor 110 embodied by the teachings of this invention is made clearer herein.

The details of the structure of the tongs, the joint sensor and the tongs control system (including an electrohydraulic interface) is discussed in detail herein.

Having defined the elements of the various structural systems, the operating sequency thereof during a typical make-up or break-out cycle is presented, to graphically illustrate the physical interractions between the defined structures Once this is done, a detailed description of each of the control systems initiating and ceasing the physical operations performed by the structural systems is set forth.

In the break-out cycle, the objective is to disassemble the drill string into its constituent pipe stands as the drill string is lifted from the bore With the upper end of the still-attached pipe stand to be next-removed held by the slips at a predetermined elevation along the vertical axis of the derrick, the traveling block with the elevator suspended therefrom is lowered under the control of the drawworks portion of the computer program and under the influence of the drawworks brake control subsystem which stops and sets the brake at an elevation so as to permit the elevator to accept the pipe stand During this period the racker is placing the last-removed pipe stand in a storage location on the set back, and will eventually be moved under control of racker portion of the computer program to a position to accept the next-removed pipe stand The drawworks program and racker program operate on a time-shared basis The tongs are in a storage position.

The computer sends an actuating signal to the elevator load control subsystem which derives its input signals from the dead line force sensor A momentary signal output from the computer samples the weight of the unloaded traveling block and elevator.

This tare weight is used to ascertain the instantaneous loading on the traveling block and elevator The elevator then accepts the loading of the drill string, and an output feedback signal to that effect from the elevator load control subsystem, is used to coordinate opening of the slips The computer outputs a momentary load sample signal before the velocity of the loaded elevator is increased This static or initial load signal is used when modified by a predetermined fractional multiplier, as a basis for determining whether the instantaneous loading on the elevator has exceeded a permissible range of, values as selected by an experienced drilling operator.

In response to an actuating signal from 70 the computer, the drawworks motor control subsystem provides a throttle signal to the drawworks motor drive to hoist the drill string to a predetermined elevation It may be necessary to move the block slightly, or 75 creep to engage the drawworks clutch The drill string is hoisted under the control of the drawworks motor control subsystem A logic network operates to release the brake whenever the hoisting velocity exceeds a 80 preset threshold value and tends to apply the brake at hoisting speeds below this threshold velocity (the drum brake being a self-energizing brake).

The motor control subsystem provides 85 output signals to the drawworks motor drive to lift the drill string in a manner which takes into account the position error (the difference between the actual position and command position of the drill string being 90 lifted), a predetermined command velocity output by the computer, and the dynamic loading During the major portion of the travel the load is hoisted at an uniform velocity equal to the command velocity As the 95 predetermined command position is approached, the hoisting velocity is reduced in a manner proportional to the position error Put another way, the drawworks motor control subsystem responds to posi 100 tion and velocity feedback signals input to it from the block position and speed transducer and the drum tachometer, respectively, to move the traveling block and elevator to a predetermined command ele 105 vation at a predetermined command velocity output by the computer.

Dunng the hoisting operation, signals from the elevator load control subsystem are taken into consideration in determining 110 the magnitude of the output signal to the drawworks motor For if the actual loading on the elevator exceeds the predetermined value by which actual load may deviate from the static loading, the motor is slowed to 115 bring the loading into the acceptable limits.

Of course, if the deviation goes beyond a threshold above even the scaled initial value range, indicating that the string is caught in the bore, the automated control shuts the 120 system down and the system reverts to manual control.

As the block is hoisted and approaches the final position; the motor is stopped and the brake is set The brake is applied when 125 the lifting velocity drops below the predetermined threshold mentioned The motor is stopped when the position reaches within some predetermined close distance to the command elevation During lifting, if 130 1 592 943 the block is indicated as moving in the wrong direction of travel or at a greater than commanded velocity, the automated sequence is halted and the system reverts to manual control.

The block final elevation is selected such that the height at which the upper end of the pipe stand to be removed finally stops will also place the joint between the pipe stand and the next lower pipe stand at an elevation for operation by the power tongs When the block velocity is sufficiently close to zero, a zero velocity signal is returned to the computer This signal, along with a block position feedback signal sufficiently close the the command position signal are necessary conditions before the actuating command to set the slips to retain the load is output from the computer Only with the slips set and supporting the full load of the drill string will the elevator relinquish the pipe stand to the racker structure As mentioned, after racking the previous stand, the racker is moved back toward the vertical centerline of derrick, so as to be in a position to accept the next pipe stand The elevator and block are retracted away from the vertical centerline of the derrick and drop under the control of the drawworks brake to be in position to repeat the lifting sequence.

When the lifting movement started, the power tongs were in the storage position above the floor of the derrick After the elevator had been hoisted above a potentially obstructing position the tongs were actuated and moved to a standby position.

After the pipe stand has been finally positioned and the slips set, a joint sensor associated with the tongs controls a slower lifting movement to bring the tongs into operating position When the tongs are positioned properly with respect to the joint, the motion thereof is halted, and the joint sensor retracted The tong backup then engages the drill string, the tong jaws engage the pipe stand to be removed, and the pipe stand is separated therefrom The racker then begins to store the nowseparated pipe stand, while the tongs are moved to the storage position The elevator then is brought into the elevation along thecentral axis of the derrick where it may engage the upper end of the still-attached pipe stand to be next-removed and the breakout process repeated.

In the make-up cycle, the objective is to assemble the drill string from its constituent pipe stands and to lower the string into the bore With the upper end of the lastconnected pipe stand supported at a predetermined elevation by the slips, the drawworks motor control subsystem lifts the block and elevator along the vertical axis of the derrick to a position at which it will receive a pipe stand from the racker.

The tongs are moved upwardly from the storage to the standby position at a first, normal, speed The tongs continue to move upwardly at a second, slower, speed beyond 70 the standby position with the joint sensor extended When the joint is sensed, upwardly motion is halted with the tongs at the operating elevation and the backup is closed A pipe stabber is extended to guide 75 the lower end of the pipe stand being made up into the threaded connection at the distended upper end of the drill string When the pipe is stabbed, the tongs proceed to make up the joint Thereafter, the tongs are 80 lowered to the storage position The elevator, at the upper elevation, is raised at a creep speed to acquire the drill string load.

After the elevator load control subsystem detects that the drill string load is acquired 85 by the elevator, the slips are raised and the drill string is hoisted further to disengage the slips from the drill string At this time, the rackers, under control of the computer racker program, proceed to acquire the next 90 pipe stand and carry it toward the vertical centerline of the derrick to the racker standby position From there the rackers proceed to the vertical centerline of the derrick 95 In response to command velocity and command position signals output from the computer, and utilizing a position feedback signal from the block position and speed transducer, and a velocity feedback signal 100 from the drawworks drum tachometer, the drawworks brake control subsystem supervises the lowering of the drill string to a predetermined lower elevation The brake control subsystem outputs control signals to the 105 drawworks brake actuator so as to maintain the block velocity near the command velocity for the major portion of the travel, and to position the block as close as possible to the command position during the final position 110 of the travel.

The elevator load control is activated by the computer and is responsive to a momentary signal to sample the loading of the block and elevator in the unloaded condi 115 tion This signal is used to discern whether or not the elevator is supporting any of the drill string load Also in response to a signal output from the computer, the loading on the elevator is sampled and held after the 120 load is acquired but before the downward velocity thereof is appreciable This initial static loading signal is used, when appropriately modified by a predetermined factional multiplier, as the basis for determination as 125 to whether or not the instantaneous loading on the elevator has exceeded a permissible range of loading normally anticipated during a lowering operation.

During the lowering operation, the out 130 1 592 943 puts to the brake actuator from the brake control subsystem take into account the signals relative to loading from the elevator load control subsystem If the actual loading is deviating from the initial static condition by more than the specified amount, the drawworks brake control slows the velocity to bring the loading back to acceptable limits If the actual loading is deviating by more than a predetermined threshold below the scaled static value (indicating that the bore is obstructed and the drill string unable to penetrate), then the automated control sequence is terminated, reverted to manual control, and the system is shut down Other interrupt conditions may occur if, during the lowering operation, an indication that excessive speed has been reached, or that the block is moving in a wrong direction of travel.

As the block reaches the command posi tion, the differences in the actual position and velocity from the command position and velocity are such that the brake is set.

That is, when the block and elevator come within a predetermined distance of the command position, the brake is set Zero position error and zero velocity are necessary conditions which must be met before the computer sets the slips With the slips set, and the weight of the drill string supported thereby, the elevator surrenders the load, and the block and elevator lifted to the upper most position to accept the next-to-be lowered pipe stand The process is then repeated.

Although the power tongs structural system 28 is not previously described in detail in connection with Figure 2, power tongs for making and breaking joints between a pipe stand and a drill string are well-known in the art For example, United States Patent 3,881,375, issued to Robert R Kelley and assigned to the Assignee of the present invention, discloses the basic structure of a power tongs assembly In Figure 3, shown is a highly stylized pictorial representation of a power tongs assembly 1000 Figure 3 illustrates the main structural elements common to all power tongs assemblies and also diagrammatically illustrates additional structural elements provided in accordance with this invention.

The tongs assembly 1000 is located adjacent to the slips 55 (Figure 2) provided on the floor 53 of the derrick 20 As is typical and well-known to the art, the tongs 1000 are mounted on a vertical column 1001, itself mounted on bearings 1002 to permit the tongs 1000 to swing into and out of alignment with the bore being generated A collar 1003 is mounted, as by rollers 1004, for movement along the vertical column 1001 A tongs supporting yoke 1005 is mounted to the collar 1003 and projects horizontally therefrom The yoke 1005 supports a cradle 1006 in which a backup tong 1007 and a power driven tong 1008 are disposed The backup tong 1007 is adapted to hold one (usually the lower) section of the 70 pipe sections defining the joint to be madeup or broken-out against rotation while the driven tong engages the other section to rotate the same in a predetermined direction The direction of rotation depends upon 75 whether the joint is being made-up or broken-out.

Also mounted on the column 1001 in any suitable relationship thereto (shown in Figure 3 as being in cooperative association 80 with the collar 1003) is a stabber 1009 As is well-known to those skilled in the art, the stabber 1009 may or may not be provided in a conventional tongs assembly, but if it is so provided, the stabber 1009 is operative to 85 assist in locating or "stabbing" the next pipe stand to be added to the drill string during a make-up cycle Since the structures discussed are conventional, it is understood that any suitable configuration of elements 90 exhibiting these functions and operating to effect the make-up or break-out of a joint in the drill string may be controlled by a control system 29 embodying the teachings of this invention 95 As is also conventional in the art, a tongs lifting arrangement 1010 is provided The arrangement 1010 comprises means for lifting the tongs from a lower, or storage, position to an upper, or standby, position and, 100 past the standby postion to a still-further upward operating position Any suitable means may be utilized, as illustrated by the piston-cylinder arrangement associated with a chain drive Fluid, such as pressurized 105 hydraulic oil, for controlling the lifting and lowering motion of the tongs is conducted from a fluid supply to the piston-cylinder arrangement 1010 on a fluid line 1011 The speed at which the tongs is raised from the 110 storage to the standby positions and from the standby to the operating positions is regulated by the fluid in a line 1012 having a restrictor 1013 therein.

Included within the backup tong 1007 is 115 means 1014, such as a piston-cylinder arrangement, for opening and closing the backup tong 1007 Fluid, such as pressurized hydraulic oils for operating the pistoncylinder arrangement 1014 is conducted 120 thereto on a line 1015 Similarly, means 1017, such as a tongs motor, are provided in operative association with the driven tong 1008 for opening and closing the jaws of the power driven tong and for rotating the 125 power driven tong 1008 in a predetermined direction to effect the make-up or break-out of the joint Fluid for operating the tongs motor 1017 is carried on a line 1018 to a cylinder 1019 related thereto Means 1020, 130 1 592 943 such as a piston-cylinder arrangement is associated with the stabber 1009 for controlling the extension thereof Fluid, such as pressurized air, utilized to energize the piston-cylinder 1020 is conducted thereto on a line 1021 Each of these above means for lifting the tongs at a predetermined lift speed, for opening and closing the backup tong, for closing the tong motor jaws and rotating the same, and for extending the stabber, are conventional in the art and any arrangement to accomplish the recited functions may be made compatible with the control system 29 embodying the teachings of this invention.

The tongs 1000 also include a joint sensor arrangement 1025 Although the joint sensor 1025 is described in complete detail in connection with Figures 18 A and 18 B, it generally comprises a sensor arrangement having a pivotally mounted roller arm with limit switch associated therewith such that deflection of the arm by a predetermined gortion of a drill pipe (as, for example, the ox end taper) actuates the limit switch.

When the limit switch is actuated, it is then known that a predetermined location on the drill pipe has been reached by the roller.

Further, due to the standardization of drill pipes for oil drilling work, it is also known that any another feature of the pipe, such as the joint itself, is then a predetermined known distance from the location on the pipe which energized the limit switch.

The joint sensor 1025 includes means 1026, such as a piston-cylinder arrangement, for extending the sensor to contact the pipe Fluid (such as pressurized air) to actuate the extension means 1026 is carried by a line 1027.

In a conventional arrangement, a manually operated valve 1030 is disposed in association with the fluid line 1011 (LIFT) to regulate the flow of fluid therein The valve 1030 is usually operable in two directions to energize the lift means 1010 for upward or downward movement of the tongs along the vertical column 1001 A manual valve 1031 is associated with the fluid line 1012 (LIFT SPEED) and is manually operable to adjust the speed at which the tongs are raised Usually, the speed is variable from a first, normal, speed exhibited during movement of the tongs from the storage to the standby positions, to a second, slower, speed exhibited during movement of the tongs from the standby to the operating positions during which time the sensor is extended to sense the joint.

A manually operated valve 1032 is associated with the hydraulic line 1015 (BACKUP) to regulate the flow of hydraulic fluid therein to the backup 1007.

Manual actuation of the valve 1032 controls the opening or closing of the backup tong 1007, as is appreciated by those skilled in the art A valve 1033 is associated with the fluid line 1018 (TONG) connected to the tongs motor 1017 to control the opening and closing of the power driven tong 1008 70 and the rotation thereof The valve 1033 is similar to the valve 1030 and is a twodirection manual valve which in one position operates the tongs motor 1017 to make up a drill string while in the other position 75 operates the tongs motor 1017 to break out a joint in the drill string.

If a stabber 1020 is utilized, a manual valve may be provided therefor operative to control passage of fluid in the lines 1021 80 (STABBER) to extend or retract the stabber Further, it would be appreciated by those skilled in the art if a joint sensor 1025 embodying the teachings of this invention is utilized in a manual tongs assembly, the 85 extension of the joint sensor may be manually effected through the provision of an appropriate manual valve regulating the flow of fluid (such as pressurized air) on the lines 1027 (SENSOR) to control the exten 90 sion and retraction thereof.

Since, in the conventional arrangement above-described (with the exception of the joint sensor 1025), the control of the tongs structure is effected by the manual manipu 95 lation of valves in the fluid lines, it would be advantageous to provide an automated electronic control system, such as the tongs control system 29 (Figures 1 and 6), to electronically operate the tongs structure Such a 100 control system is provided by this invention.

However, since the outputs of the control system 29 are electrical control signals, and since the above-discussed conventional tongs assembly utilizes fluid energized 105 operators, it is necessary to provide an electro-hydraulic interface (E H I) module intermediate between the tongs control system 29 and the tongs structure 28 controlled thereby This module is illustrated diag 110 rammatically in Figure 3 and discussed in complete detail in connection with Figure 4.

Each interface module is generally indicated by reference numeral 1028 and is provided to disenable the manually operated valve 115 with which it is associated and to substitute therefor an electrically responsive valve adaptable to be controlled by the electrical output signals from the tongs control system 29 120 In general, the interface module 1028 includes an electrically operated solenoid valve connected in parallel relationship with the manually operated valve and in the same cooperative relationship with the fluid line 125 through which the structure of the tongs communicates with the source of fluid therefor Further, each interface module includes means for selectively enabling the electrically operated valve and simultaneously dis 130 1 592 943 enabling the manual valve The select means can conveniently be an electrically or manually operable switch arrangement, or any other suitable arrangement Thus, dependant upon the operative mode (automatic or manual) selected, either the electrically operated valve or the manually operated valve will be determinative as to the passage of hydraulic fluid in the lines with which it is associated.

As seen in Figure 3, four interface modules 1028 A, 1028 B, 1028 C and 1028 D are provided so as to make the above-described conventional system responsive to the electrical signal outputs from the tongs control system 29 (Of course, if a conventional system utilized other manually operated valves, an interface module could be provided to make the function provided by that manually-operated valve electrically controllable) The interface module 1028 A (LIFT) is associated with the fluid line 1011 and controls movement of the tongs 1000 in a vertically upward and vertically downward direction Since the manually operated valve 1030 with which the interface 1028 A is associated is a four-way valve, the electrically responsive valve connected in parallel relationship to the valve 1030 within the interface 1028 A is similarly a four-way valve Therefore, electrical lines 1035 (LIFT UP) and 1036 (LIFT DOWN) are input to the interface module 1028 A from the tongs control system 29 The presence of a signal on the appropriate line 1035 (LIFT UP) or 1036 (LIFT DOWN) from the tongs control system 29 initiates, respectively, an upward lifting movement of the tongs 1000 and a downward movement thereof.

The interface module 1028 B is associated with the manually operated valve 1031 and includes a valve connected in parallel relationship thereto which is responsive to an electrical signal on an electrical line 1037 (LIFT SPEED) to control the rate at which upward speed of the tongs 1000 is effected.

The interface module 1028 C includes a valve connected in parallel relationship with the manually operated valve 1032, the interface valve being responsive to a signal on an electrical line 1038 (BACKUP) from the tongs control system 29 Energization of the line 1038 with the manual valve 1032 disenabled actuates the electrically responsive valve within the interface module 1028 C to effect the closing of the backup tong 1007.

Interface module 1028 D includes an electrically responsive valve connected in parallel relationship with the manually operated valve 1033 and is actuable to control to the tongs motor 1017 to make-up or break-out a joint Since the manually operated valve 1033 is operable in two-directions, the electrically responsive valve within the interface module 1028 D is responsive to signals from the tongs control system 29 on electrical lines 1039 (TONG MAKE) or 1040 (TONG BREAK) to respectively initiate motion of the tongs motor 1017 to drive the driven tong 1008 to make-up or break-out 70 the joint It is understood that if other manual control valves were provided in a particular manually operated tongs assembly, suitable interfaces embodying the teachings of this invention may be provided to auto 75 mate the functions performed thereby and make control thereof possible by the use of the tongs control system 29 embodying the teachings of this invention.

A four-way single solenoid, spring offset 80 electrically responsive valve 1041 responds to an electrical signal on a line 1042 (EXTEND STABBER) from the tongs conrol system 29 to control the passage of fluid in the line 1021 to actuate the piston 85 cylinder arrangement 1020 to extend or retract the stabber 1009 A four-way, single solenoid, spring offset electrically responsive valve 1043 (similar to the valve 1041) responds to an electrical signal from the 90 tongs control system 29 on a line 1044 (EXTEND SENSOR) to actuate the piston-cylinder arrangement or other suitable extension means 1026 disposed within the joint sensor 1025 It is, of course, under 95 stood that if either of these last two functions were provided by a manually operated control valve in a particular manually operated tongs assembly, a suitable interface module would be provided to disenable the 100 manually operated valve and selectively enable the electrically responsive valve to permit automated control of the tongs assembly by a control system embodying the teachings of this invention 105 In order to provide automated control of the tong structure 28, suitable feedback signal generating means, commonly limit switches, are disposed at predetermined locations within the structure of the tongs 110 An upper limit switch 1045 is disposed so as to output a signal on a line 1046 (TONGS IN STANDBY OR ABOVE) to the tongs control system 29 representative of the fact that the tongs have been raised on the col 115 umn 1001 to at least the standby position A lower limit switch 1047 is mounted within the tongs structure 28 and outputs a feedback signal on the line 1048 (TONGS IN STORAGE) to the tongs control system 29 120 representative of the fact that the tongs are in a storage position along the vertical column 1001.

Suitable means, as a pressure sensing switch 1049 disposed on the backup tong 125 1007 outputs a feedback signal on a line 1050 (BACKUP CLOSED) to the tongs control system 29 representative of the fact that the backup tong is in the closed and locked condition Similarly, a limit switch or 130 1 592 943 other suitable detector 1051 outputs an electrical signal on a line 1052 (BACKUP OPEN) to the tongs control system 29 representative of the fact that the backup tong 1007 is open Suitable means, such as limit switch 1053, outputs a signal on a line 1054 (STABBER NOT EXTENDED) to the tongs control system 29 representative of the fact that the stabber 1009 is in the extended or not extended position Feedback signal generating means, such as a switch or pressure transducer 1055, disposed on the tongs makeup cylinder 1019 associated with the tongs motor 1017, outputs a signal to the tongs control system 29 on a line 1056 (TORQUED UP) indicative of a fully torqued condition of the tongs motor 1017 and representative of the fact that during a make-up cycle ther joint has been adequately made-up.

The joint sensor 1025 embodying the teachings of this invention includes feedback signal generating means such as limit switch 1057 outputting a signal on a line 1058 (JOINT SENSOR RETRACTED) to the tongs control system 29 representative of the fact that the joint sensor is in the retracted position When a joint is sensed, a feedback signal from the limit switch 1059 associated with the detector in the joint sensor 1025 outputs a signal on a line 1060 (JOINT SENSED) to the tongs control system 29 representative of the fact that the joint has been sensed.

A full discussion of the manner in which the above-listed feedback signals are utilized by the tongs control system 29 to energize appropriate ones of the output lines to the electrically responsive valves located within the interface modules 1028 is discussed fully in connection with the tongs control system 29, herein.

Referring now to Figure 4, a detailed schematic diagram of each of the interface modules 1028 A through 1028 D is shown.

Each of the interface modules 1028 includes an electrically responsive solenoid valve adapted to control the flow of hydraulic fluid from a supply, or source, thereof to the respective user apparatus with which the interface module is associated Whether the manually operated valve (and therefore, the electrically responsive valve disposed within each interface) is a pilot valve (in the sense of initiating the operation of a larger valve) or is a control valve (in the sense of interdicting the flow of hydraulic fluid) is a design consideration dependent upon the particularities of a given tongs system The electro-hydraulic interface module is an adjunct to the tongs control system 29 and is adapted to disenable the manually operated valve and replace it with an electrically responsive valve which performs the same function as performed by the manually operated value Thus, if the manually operated valve were a pilot valve, the electrically responsive valve in the interface would assume a pilot valve function Alternatively, if the manually operated valve were a con 70 trol valve, the electrically operated valve in the module would assume a control valve function The electrically operated valve is connected in a parallel flow path to the manually operated valve Further, each 75 interface module 1028 A through 1028 D includes means, such as a select valve switch, disposed in series with the electrically responsive valve and with the manually operated valve to simultaneously disenable 80 one of the valves and enable the other of the valves The select valve switches may be manually or electrically operated, and are illustrated as electrically operated in connection with Figure 4 85 The select valves or switches are all energized by the same source, namely the AUTO/MANUAL BUS from the tongs control system 29 The manual valves are enabled whenever the AUTO/MANUAL 90 BUS is de-energized and the electrically responsive valves are disenabled The electrically responsive valves enabled when the AUTO/MANUAL BUS is energized to simultaneously energize all select valves 95 As seen in the schematic diagram of the interface module 1028 A, the four-way manually operated value 1030 with which the module is associated is also illustrated.

An electrically responsive four-way solenoid 100 valve 1065, connected in parallel relationship with the manually operated valve 1030, has solenoid coils 1066 A and 1066 B associated therewith Connected in series with the electrically responsive valve 1065 is an 105 AUTO-MA Nt AL SELECT valve switch 1067, while connected in series to the manually operated valve 1030 is an AUTOMANUAL SELECT valve switch 1068.

Actuation of all of the select valve switches 110 simultaneously enables either the electrically responsive or manually operated valves and simultaneously disenables the other.

The solenoid coil 1066 A is connected to the electrical line 1035 (LIFT UP) from the 115 tongs control system 29 while the solenoid coil 1066 B is connected to the electrical line 1036 (LIFT DOWN) from the tongs control system 29 The presence of a signal on the line 1035 (LIFT UP) energizes the coil 120 1066 A and lifts the tongs from the storage to the standby position Analogously, the presence of a signal on the line 1036 (LIFT DOWN) energizes the coil 1066 B and lowers the tongs from the standby to the storage 125 position.

The interface module 1028 B is associated with the manually operated valve 1031 An electrically responsive solenoid valve 1069 is connected in a parallel hydraulic path to 130 In 1 592 943 the manually operated valve 1031 The valve 1069 has a solenoid coil 1070 associated therewith AUTO/MANUAL SELECT valve switches 1071 and 1072 are, respectively, connected in series with the electrically responsive solenoid valve 1069 and the manually operated valve 1031 for purposes analogous to those discussed in connection with the select valve switches 1067 and 1068 The solenoid coil 1070 of the electrically responsive valve 1069 is connected to the electrical line 1037 (LIFT SPEED) output from the tongs control system 29 If the select valve switches 1071 and 1072 are disposed so as to simultaneously disenable the manually operated valve 1031 and enable the electrically responsive valve 1069, the presence of a signal on the line 1037 (LIFT SPEED) actuates the valve 1069 to regulate the speed at which the tongs are lifted from a first to a second elevation.

The interface module 1028 C operates exactly as the structure described in connection with the module 1028 B An electrically responsive valve 1074 having a solenoid coil 1075 attached thereto is connected in a parallel hydraulic path to the manually operated valve 1032 AUTO/MANUAL SELECT valve switches 1076 and 1077 are respectively connected in series with the electrically responsive valve 1074 and the manually operated valve 1032 The solenoid 1075 is connected to the electrical line 1038 (BACKUP) from the tongs control system 29 If the select valve switches 1076 and 1077 are disposed so as to disenable the manually operated valve 1032 and to simultaneously enable the electrically responsive valve 1074, the presence of a signal on the line 1038 (BACKUP) from the tongs control system 29 actuates the valve 1074 to close the backup tong 1007.

The interface module 1028 D is similar in configuration to that discussed in connection with the interface module 1028 A That is to say, a four-way electrically responsive solenoid valve 1078 having first and second solenoid coils 1079 A and 1079 B associated therewith is connected in a parallel hydraulic path to the four-way manually operated valve 1033 AUTO/MANUAL SELECT valve switches 1073 A and 1073 B are respectively connected in series to the electrically responsive valve 1078 and the manually operated valve 1033 The solenoid 1079 A is connected to the line 1039 (TONG MAKE) from the tongs control system 29 while the solenoid 1079 B is connected to the line 1040 (TONG BREAK) output therefrom If the select valve switches 1073 A and 1073 B were disposed so as to simultaneously disenable the manually operated valve 1033 and enable the electrically responsive valve 1078, the presence of a signal on the line 1039 (TONG MAKE) would actuate the electrically responsive valve 1078 to enable the tongs motor 1017 to make-up a joint of a drill string The presence of a signal on the line 70 1040 (TONG BREAK) from the tongs control system 29 actuates the solenoid 1079 B and energizes the tongs motor 1017 to break-out a drill string joint.

Since each of the four interface modules 75 1028 have substantially the same internal hydraulic circuitry and utilize substantially similar type valves, the same supply manifold may be utilized to reduce cost and provide a symmetrical electro-hydraulic inter 80 face assembly The interface modules may be mounted on a common base and connected to common pressure and tank manifolds A pressure-reducing valve and accumulator may, of course, be included to 85 supply a constant pressure Suitable hyd-raulic line tubing may be used to connect the valve manifolds and pressure-reducing valve to the common manifolds and to the input and output header plates of the electro 90 hydraulic interface.

The tongs control system 29 cannot equal the cycle times possible with the manual controls operated by experienced man.

However, it does not make common mis 95 takes such as forgetting to close the backup before rotating the tong, which sometimes happens with a man at the controls, or positioning the tong too-high or too-low on the tool joint The cycle times of the tongs con 100 trol system 29 are fast-enough, however, since the tongs sequence is coordinated with the racker and drawworks sequences The tongs cycle does not cause a delay in the overall program sequence 105 Figure 6 is a detailed schematic diagram of a tongs control system 29 embodying the teachings of this invention However, before embarking upon a detailed discussion of the circuitry of the tongs control system 29, 110 reference is directed to Figure 5 which illustrates the interconnections between the tongs control system 29 with the computer The interconnections between the tongs control system 29 and the tongs structural 115 system 28 have been discussed in connection with Figure 3, but are reproduced on Figure 5 for clarity As seen from Figure 5, the computer 40 outputs signals to the tongs control system 29 on a line 1080 (SELECT 120 SEQUENCE), which signal represents a command from the computer 40 for the tongs control system 29 to execute either a make-up or a break-out cycle The line 1081 (RAISE TONGS) carries a signal from the 125 computer to the tongs control system 29 initiating the raising of the tongs along the vertical column 1001 (Figure 3) from the storage to the standby position A line 1082 (START SEQUENCE) carries a command 130 1 1 1 592 943 signal from the computer 40 to the tongs control system 29 initiating the start of the selected sequence.

Upon the receipt of the START SEOUENCE signal on the line 1082, the circuitry of the tongs control system 29 initiates operation of the tong's physical structure to perform the operations necessary to either make-up or break-out a drill string These command signals from the tongs control system 29 have been detailed in connection with Figure 3 Some of the command signals, as discussed, must be interfaced through the electro-to-hydraulic interface shown in Figure 4 The tong control system 29 is input with various feedback signals representative of the physical occurrence of certain actions within the tongs structure.

These feedback signals from the means provided on the tongs structure have been detailed in connection with Figure 3.

The tongs control system 29 outputs signals back to the computer On the line 1084 (STABBER EXTENDED), and output signal is carried to the computer 40 indicating that the stabber ( 1009, Figure 3) has been extended This signal is meaningful only during the make-up sequence and provides information necessary to continue the pipe racker program A line 1085 (BACKUP OPEN) carries information to the computer 40 representative of the fact that the backup tong 1007 is open Finally, the tongs control system 29 outputs a signal on a line 1086 (SEQUENCE COMPLETE) representative of the fact that the selected cycle is complete and that the tongs have been returned to the storage position.

Referring now to Figure 6, a detailed schematic diagram of the tongs control system 29 is illustrated The operation thereof may be more fully understood by reference to Figure 7 A and 7 B which are, respectively, timing diagrams for the tongs control system 29 shown in Figure 6 in the make-up and break-out cycles.

In a computer controlled oil drilling rig embodying the teachings of this invention, the computer coordinates and sequences the operation of the tongs, drawworks and racker The operating philosophy is to utilize a time-shared arrangement between the drawworks and racker control programs, with a minimum of interaction between the computer and the tongs Basically, the computer initiates the selected tongs activity at the appropriate place in the cycle, with the activity being controlled by the tongs control system Necessary signals from the tongs control to the computer to enable it to sequence the drawworks and racker are provided When the tongs activity is completed a signal to this effect is sent to the computer.

It may also be noted that the control system shown in Figure 6 is able to be utilized in connection with any power tongs structure due to the similarity of the operating elements As discussed, all power tongs require a lift and lift speed controls, back-up 70 tong controls, power driven tong controls, as well as initiation signals to a stabber (if one is provided) and an initiation signal for operation of a joint sensor Thus, the control system disclosed herein is adaptable and 75 useful with any power tongs Although the initiating signals to the control system originate from a digital computer, it is understood that the initiating instructions may be provided to the control system 29 through a 80 push-button control box, thus making the control "manual" (in the sense that the sequencing signals to the tongs control originate from a human operator as opposed to a digital computer) but still "automatic" 85 (in the sense that valves regulating the flow of pressurized fluid to the tongs structure are operated by the electrical signal outputs of the tongs control system) All of the feedback signals from the tongs 90 structure 28 are applied to the tongs control 29 through filter elements 1090 as shown in Figures 6 A and 6 C Each element 1090 contains a two-pole, low-pass filter to remove transients It also contains a diode limiter to 95 limit the magnitude of the input signal to a level compatible with the succeeding logic components.

In a make-up cycle, the signal from the computer on the line 1081 (RAISE 100 TONGS) provides a logic signal to raise the tongs to the standby position The RAISE TONGS signal on the line 1081 is filtered and limited, as discussed above, and applied to a delay circuit 1093 including a multivib 105 rator A, inverters B and C and a NOR gate D The delay circuit 1093 provides a predetermined delay so that the duration of an incoming signal on the line 1081 must last at least the predetermined delay interval (for 110 example, 0 3 seconds) before it is passed into the control logic The delay 1093 provides additional protection against line transients causing a false signal.

The output of the delay circuit 1093, and 115 specifically the output of the NOR gate D, clocks a LIFT UP flip-flop 1094 When clocked, the O output of the LIFT UP flipflop 1094 goes to a logic 1 and that signal is amplified by an amplifier 1095 and applied 120 to a transistor 1096 causing it to conduct.

The output signal on the line 1035 (LIFT UP) is applied to the E H I 1028 A to raise the tongs in an upward direction from the storage toward the standby position The 125 output of the delay network 1093 also resets and BACKUP CLOSED MEMORY flipflop and the JOINT SENSED MEMORY flip-flop, as illustrated by the reference characters Z-Z 130 1 592 943 At the standby position, a feedback signal on the line 1046 (from the upper limit switch 1045 (Figure 3)) generates a LIFT SPEED signal on the line 1037 to shift the speed of the upward motion of the tongs to slow The output signal on the line 1037 (LIFT SPEED) is derived through an inverter 1097, a NOR gate 1098, an amplifier 1099 and a transistor 1100 The NOR gate 1098 derives its other input from the Q output of the LIFT UP flip-flop 1094 The same signal from the output of the inverter 1097 clocks a JOINT SENSOR flip-flop 1102 The clock signal is derived from a NOR gate 1103 which derives its inputs from the Q output of the network 1092 and the output of the inverter 1097, both of which are at logic 0 at this time The data input to the flip-flop 1102 is derived from the output of a NOR gate 1104 The inputs to the gate 1104 (both of which are at logic 0 at this time) are derived from the output of the inverter 1097 and from the Q output of the LIFT UP flip-flop 1094 The Q output of the flip-flop 1102 is applied through an inverter 1105 and a transistor 1106 to the line 1044 (EXTEND SENSOR) to extend the joint sensor 1025 (Figure 3) The sensor 1025 is extended only when the tongs are being lifted and only when the tongs are above the standby position.

The slow upward motion of the tongs continues until a JOINT SENSED feedback signal is received from the joint sensor 1025 on the feedback line 1060.

The JOINT SENSED feedback signal on the line 1060 generates several responses within the tongs control network 29 The signal on the line 1060, after appropriate filtering and limiting, resets the LIFT UP flip-flop 1094 through an amplifier 1108 to thereby stop the upward motion of the tongs A JOINT SENSED signal also resets the JOINT SENSOR flip-flop 1102, again derived through the amplifier 1108, to retract the joint sensor 1025 Thirdly, the JOINT SENSED signal on the line 1060 sets a JOINT SENSED flip-flop memory 1110 as illustrated by reference characters W-W Finally, the JOINT SENSED signal on the line 1060 causes the stabber 1109 (Figure 3) to extend by clocking a STABBER flip-flop 1112 which applies a signal through an inverter 1114 and a transistor 1115 to the line 1042 (EXTEND STABBER) The STABBER flip -flop is clocked through a NOR gate 1117 The NOR gate 1117 derives its inputs from the output of the amplifier 1108 and from the Q output of the Schmitt trigger network 1092.

The receipt of a JOINT SENSOR RETRACTED signal on the line 1058 from the limit switch 1057 (Figure 3) clocks a BACKUP flip-flop 1119 The output of the BACKUP flip-flop 1119 generates a signal on the output line 1038 (BACKUP) through an inverter 1120 and a transistor 1121 to close the backup tong 1007 A feedback signal STABBER EXTENDED from the switch 1053 is output on the line 70 1084 to the computer 40.

At this point in the sequence there is a pause until a signal is received on the line 1082 (START SEQUENCE) from the computer (Figure 5) commanding that the 75 joint make-up sequence be started This signal is conducted through a delay circuit 1124 comprising a multivibrator E, inverters F and G and a NOR gate H The delay network 1112 acts to impose a predeter 80 mined delay (for example, 0 3 seconds) such that the interval of any incoming signal on the 1082 must be at least 0 3 seconds in duration before it is passed The output of the delay network 1124, and specifically the 85 NOR gate H, resets the STABBER flip-flop 1112, retracting the STABBER 1109 (Figure 3) The output signal from the delay circuit 1124 provides one input to an AND gate 1126 through an inverter 1127 and a 90 NOR GATE 1128 The NOR gate 1128 derives itsinputs from the inverter 1127 and from the Q output of the bistable network 1092 The second input to the AND gate 1126 is derived from a feedback signal from 95 the switch 1053 on the line 1054 indicating that the stabber is not extended.

The output of the AND gate 1126 is applied to a NOR gate 1130 which derives its other input from an inverter 1131 The 100 inputs to the inverter 1131 are derived from a feedback signal on the line 1058 (BACKUP CLOSED) from the limit switch 1049 (Figure 3) The input on the line 1058 BACKUP CLOSED) is applied to a delay 105 circuit 1133 for reasons similar to those discussed above The delay circuit 1133 includes a multivibrator I, an inverter J, and a NOR gate K The output of the delay network 1133 is applied to the inverter 1131 110 and also sets a BACKUP CLOSED MEMORY flip-flop 1134.

The output of the NOR gate 1130 sets a MAKE-UP flip-flop 1135 The Q output of the MAKE-UP flip-flop 1135 enables the 115 appropriate one ( 1137 A) of the NAND gates 1137 A and 1137 B through a diode 1138 The second input to the NAND gate 1137 A is derived from the Q output of the bistable network 1092 as illustrated by the 120 reference characters U-U The second input to the NAND gate 1137 B is derived from the Q output of the network 1092 as illustrated by the reverence characters V-V.

The output of the enabled NAND gate 125 1137 A is applied to the line 1039 (TONG MAKE) through a diode 1139, an inverter 1140, and a transistor 1141 This causes the jaws of the power driven tong to close and to rotate clockwise to make-up the joint 130 1 592 943 The output of the NAND gate 1137 B, which is not enabled during the make-up mode, is applied to the line 1040 (TONG BREAK) through a diode 1143, an inverter 1144 and a transistor 1145 The tongs motor 1017 is rotated until a TOROUED UP signal on the line 1056 is received from the feedback means 1055 on the makeup cylinder (illustrated as a switch in Figure 6 A) The signal on the line 1056 (TORQIUED UP) resets the MAKE-UP flip-flop 1135, as illustrated by the reference characters P-P, which stops the tongs motor rotation As the Q output from the MAKEUP flip-flop 1135 goes low, a pulse is applied through a capacitor 1147 and an inverter 1148 to initiate a timer 1150 (ti) comprising NOR gate 1151 A and an inverter 1151 B. The output of the timer 1150 provides an adjustable delay ti (see timing diagram, Figure 17 A), the period of which is set by a potentiometer 11 50 A.

When the time ti runs out, a pulse through a capacitor 1152 initiates a second timer 1154 comprising NOR gates 1155 A and an inverter 1155 B This timer 1154 (set by a potentiometer 1154 A) provides an adjustable time th during which the electrically controlled solenoid valve 1077 connected by the line 1040 (TONG BREAK) in the interface module 1028 A (Figure 4) is energized through a resistor 1196 and a NAND gate 1157, a diode 1158, the inverter 1144 and the transistor 1145 This signal on the line 1040 reverses the tongs motor 1017 so that it rotates clockwise to open the jaws of the power driven tong 1008 The second input to the NAND gate 1157 is derived from the Q output of the Schmitt trigger network 1092 as illustrated by reference characters U-U When time th runs out, the signal on the line 1040 terminates deenergizing the transistor 1017 At the same time, a pulse is applied through an inverter 1160, a capacitor 1161 and a diode 1162 to reset the BACKUP flip-flop 1119 which causes the backup tong 1007 to open.

A signal on the line 1052 (BACKUP OPEN) from the switch 1051 (Figure 3) clocks a LIFT DOWN flip-flop 1164 The O output (a logic 1) of the LIFT DOWN flipflop 1164 is applied to the line 1036 (LIFT DOWN) through an amplifier 1165 and a transistor 1166 to lower the tongs In addition, the signal on the line 1052 (BACKUP OPEN) is AND-ed with two other signals through diodes 1168, 1169 and 1170 The BACKUP OPEN signal is applied on the output line 1085 through the amplifier 1172 and transistor 1173 only if the JOINT SENSED MEMORY flip-flop 1110 and the BACKUP CLOSED MEMORY flip-flop 1134 have both been previously set Therefore, the BACKUP OPEN signal is output on the line 1085 to the computer is inhibited unless the tongs have been cycled through the major phases of their operational sequence.

As the tongs approach the storage position, the lower limit switch 1047 (Figure 3) 70 outputs a signal on the line 1048 to the tongs control system 29 This signal is applied through an amplifier 1175 and a diode 1176 to reset the LIFT DOWN flipflop 1164 75 Resetting of the LIFT DOWN flip-flop 1164 stops the tongs lowering motion A signal from the lower switch 1047 is also applied to the line 1086 (SEQUENCE COMPLETE) indicating that the tongs 80 sequence is completed (Figure 5) It signified to the computer that the tongs are clear of any potentially obstructing position with the elevator to permit the elevator 75 (Figure 2) to be lowered to the desired ele 85 vation.

A delay network 1178 (Figure 6 C) consisting of a resistor 1179, a diode 1180, a capacitor 1181 and an inverter 1182 function to reset all flip-flops as illustrated by 90 reference characters R-R when system power is applied It insures that all logic components are preset to the proper state at the beginning of the sequence.

The timing diagram for a break-out cycle 95 is shown in Figure 7 B During a break-out cycle, a logic 1 signal on the line 1080 (SELECT SEQUENCE) from the computer 40 transfers the logic circuits to the proper configuration Namely, the Q output 100 of the Schmitt trigger network 1092 is in a logic 0 condition while the Q output thereof is in a logic 1 condition A RAISE TONGS signal on the line 1081 sets the LIFT UP flip-flop 1094 raising the tongs, as previ 105 ously discussed The lifting motion of the tongs is halted by a feedback signal from the upper limit switch 1045 (Figure 3) on the line 1046 which is inverted the the inverter 1097, and coupled through a capacitor 1184 110 and a NOR gate 1185 to reset the LIFT UP flip-flop 1094 A pause in the tong sequence follows with the tongs remaining in the standby position.

When the tool joints is hoisted into posi 115 tion, a break-out signal is applied on the line 1082 (START SEQUENCE) through the delay network 1124 The output of the delay network 1124 clocks the JOINT SENSOR flip-flop 1102 through inverter 120 1127 and a NOR gate 1187 to extend the joint sensor 1025 The other input to the NOR gate 1187 is derived from the Q output to the bistable network 1092 The output of the delay network 1124 also clocks 125 the LIFT UP flip-flop 1094, again through theinverter 1127 and NOR 1187.

The Q output of the LIFT UP flip-flop 1094 is NOR-ed at the gate 1098 with the signal from the upper limit switch 1045 on 130 1 592 943 the line 1056 as inverted by the inverter 1097 The output of the NOR gate 1098 is applied through the amplifier 1099 and applied to the transistor 1100 switches to a conductive state The output signal on the line 1037 (LIFT SPEED) switches the tongs lifting motion to a speed slow enough to detect the joint The joint sensor is extended when the JOINT SENSOR flip-flop 1102 is clocked by a signal from the output of the NOR gate 1103 The NOR gate 1103 derives its inputs from the output of the inverter 1097 and the U output of the bistable network 1092.

As the tongs reach the desired elevation, a JOINT SENSED feedback signal on the line 1060 from the joint sensor 1025 is received The JOINT SENSED signal resets the LIFT UP flip-flop 1094 through the amplifier 1108 to stop the lift motion of the tongs The JOINT SENSED feedback signal also sets the JOINT SENSED MEMORY flip-flop 1110 as illustrated by the reference characters W-W The JOINT SENSED feedback signal also resets the JOINT SENSOR flip-flop 1102 through the amplifier 1108 to retract the joint sensor 1025 The retraction of the joint sensor 1025 generates a feedback signal on the line 1058 to clock the BACKUP flip-flop 1119.

A signal from the feedback switch 1049 on the line 1058 (BACKUP CLOSED) is applied to the delay network 1133 to prevent any initial transients as the backup starts to close from appearing as a true signal The output of the delay network 1133 sets the BACKUP CLOSED MEMORY flip-flop 1134 The output of the delay network 1133 is also applied to a NAND gate 1188 The second input tothe NAND gate 1188 is derived from the Q output of the Schmitt trigger network 1092 as illustrated by the reference characters V-V The output of the NAND gate 1188 is coupled through a capacitor 1189 to a timer 1190.

The duration of the output of the timer 1190 is an adjustable time delay t 5 (Figure 7 B) set by a potentiometer 1190 A The output of the timer 1190 is connected through a diode 1191 and switches the properly enabled NAND gate In this case the enabled gat-, 1137 B, derives its second input from the Q output of the bistable network 1092 as illustrated by reference characters V-V A signal is applied to the line 1040 (TONG BREAK) through the diode 1143, the inverter 1144 and the transistor 1145 to the tongs motor 1017 to break out the joint by counterclockwise rotation.

When the timer 1190 times out, the tongs motor 1017 is de-energized and a pulse is coupled through the capacitor 1147 and the inverter 1148 to start the ti timer 1150.

During the break-out cycle the transistors 1192 and 1193 are conducting so that the potentiometer 1150 A which normally sets the duration of ti is bypassed A long delay is unnecessary in the break-out mode When the ti timer 1150 times out, a pulse is coupled by the capacitor 1152 to initiate the t 3 70 timer 1154 The output of the t 3 timer 1154 is applied to a NAND gate 1195 through a resistor 1196 This input to the NAND gate 1195 is also coupled from the output of the inverter 1097 through a diode 1197 and an 75 inverter 1198 The second input of the NAND gate is connected to the O output of the Schmitt trigger network 1092 as illustrated by reference characters V-V.

When the output of the t 3 timer 1154 is 80 applied to the NAND gate 1195, its output switches to logic 1 and this is applied through a diode 1199 and the amplifier 1140 to the line 1039 (TONG BREAK).

This energizes the tongs motor 1017 (Figure 85 3) for the time period t 3 in a clockwise direction so as to open the jaws of the power driven tong 1008.

When the t 3 timer 1154 is timed out, a pulse is coupled through the inverter 1160, 90 the capacitor 1161 and the diode 1162 to reset the BACKUP flip-flop 1119 This opens the jaws of the backup tong 1007 A signal on the line 1052 (BACKUP OPEN) from the switch 1051 clocks the LIFT 95 DOWN flip-flop 1164 to return the tongs to the storage position This signal (BACKUP OPEN) is applied through the diode 1170 to the amplifier 1172 along with enabling signals through the diodes 1168 and 1169 to 100 switch the transistor 1173 on This output signal on the line 1085 (BACKUP OPEN) is applied to the computer only if the previously discussed preconditions have been met This signal to the computer 40 signifies 105 that the pipe stand is ready to be moved to its storage position.

When the tongs reach the storage position the switch 1047 outputs a signal on the line 1048 (TONGS IN STORAGE) to reset the 110 LIFT DOWN flip-flop 1164 halting the motion and a signal on the line 1086 (SEQUENCE COMPLETE) is output to the computer indicating that the tongs sequence is complete 115 The diodes 1201 and 1202 prevent the BACKUP flip-flop 1119 from being clocked while the tong is in motion Conversely, the BACKUP OPEN signal on the line 1052 is applied as an enabling signal to the data 120 input of the LIFT UP flip-flop 1094 as illustrated by reference characters Q-Q and the data input of the LIFT DOWN flip-flop 1164 Neither flip-flop may be clocked unless the backup is open This prevents 125 tong lift motion unless the backup is open.

Referring to Figures 8 A and 8 B, respectively shown are side elevational and top views of a joint sensor generally indicated by reference numeral 1025 The joint sensor 130 1 592 943 1025 is attached beneath the backup tong 1007 of a power tongs assembly (Figure 3) and is operative to accurately position the backup tong 1007 and a driven tong 1008 in a symmetrical relationship with the tool joint being made-up or broken-out by the tongs 1000 under the control of the tongs control system 29 Since the gripping space for the tongs dies is limited, and since considerable force must be applied to these dies, it is necessary to locate the backup tong 1007 and the driven tong 1008 as nearly as possible in vertical symmetry above and below a horizontal plane extending through the tool joint.

The joint sensor 1025 includes a sensor arrangement 1204 which comprises an arm 1206 having a roller 1208 thereon, the roller being contactable with a drill pipe and the arm being pivotally moveable with respect thereto from a first, normal, position to a second, deflected, position The detector arrangement 1204 also comprises means 1210, including the limit switch 1059, associated with the arm 1206 for generating an electrical signal on the output line 1060 (JOINT SENSED) when the arm 1206 is pivotally deflected a predetermined angular distance from the normal positon by being brought into contact with a distended location on the pipe The arm 1206 is biased into the normal position by an internal spring assembly (not shown) The means 1210 may be any suitable commercially available assembly, such as that sold by Micro under model number BZLN-2-RH.

In Figures 8 A and 8 B, the joint sensor arrangement 1204 of the sensor 1025 is mounted on a carriage 1212 disposed for movement within a suitable housing 1214.

The housing 1214 is connectable by any suitable attachment arrangement 1216 to the underside of the backup tong 1007 Disposed within the housing 1214 is a pistoncylinder arrangement 1026 (Figure 3) The piston-cylinder arrangement is in fluid communication with the lines 1027 carrying a fluid (such as pressurized air) (Figure 3) illustrated diagrammatically on Figure 8 A and are provided to extend the joint sensor from a first, horizontally retracted, position to a second, horizontally extended, position.

Included within the piston-cylinder 1026 is the limit switch 1057 which outputs an electrical signal on the line 1058 (Ji OINT SENSOR RETRACTED) to the tongs control system 29 when the sensor 1204 is in the horizontally retracted position The cylinder 1026 may provide a stroke greater than is necessary to extend the sensor 1204 to contact the pipe whose joint is to be sensed to provide an additional ability to follow any logitudinal misalignment of the pipe or irregularities in its surface, as with pipes exhibited an external upset (Figure 9) The pressure of the pressurized air in the line 1027 is sufficient to hold the extended sensor 1204 in position against the pipe It is most advantageous to use a compressible fluid, as pressurized air, so that the pressur 70 ized air in the piston-cylinder 1026 acts as a spring to allow movement of the sensor 1204 after it is extended.

The carriage 1212 has horizontal roller element 1218 engageable with guide rails 75 1220 mounted within the housing 1214 The horizontal rollers 1218 are provided to facilitate the horizontal movements of the sensor 1204 and carriage 1212 therefore in response to actuation of the piston-cylinder 80 In one embodiment of the invention, the carriage 1212 is provided with a pair of guide rollers 1222 A and 1222 B As shown in Figure 18 B, the axes of rotation of each 85 of the guide rollers 1222 define a predetermined angle 1224 of approximately 120 degrees therebetween The angularity between the guide rollers 1222 assists in centering the sensor 1204 laterally with respect to 90 the pipe Centering springs 1226 A and 1226 B are also provided between the guide rails 1220 and the housing 1214 to permit the guide rollers 1222 to align the sensor 1204 with the pipe even though the pipe 95 may not be centered within the tongs In an alternate embodiment of this invention, the guide roller 1222 and the detector roller 1208 may each be of a predetermined lateral dimension and in a parallel relationship 100 so as to be able to contact the pipe regardless of the centered orientation thereof with respect to the tongs In such a structural embodiment, the carriage 1212 is moved horizontally from the retracted to the 105 extended position by the piston-cylinder 1026 and lateral centering of the sensor 1204 on the pipe is not required.

In operation, the sensor roller 1208 moves with the tongs slowly upwardly until 110 the arm 1206 is pivotally deflected from its normally outwardly biased position against the surface of the pipe by a distended surface feature on the pipe With reference to Figure 9, it is there shown that dependent 115 upon the pipe utilized, any one of a predetermined number of distended portions on the pipe may be used to actuate the sensor arrangement embodying the teachings of this invention The location on the box end 120 taper (Figure 9) having a predetermined diameter of approximately 5 70 inches when using 5 00 inch drill pipe, is such a convenient location on the pipe When the predetermined location on the pipe is encoun 125 tered by the sensor roller 1208 and the arm 1206 is pivotally deflected from the normal position, the switch 1059 emits an electrical signal on the line 1060 that the joint has been sensed When the predetermined loca 130 1 592 943tion on the pipe is encountered, the distance 1230 from that location to the joint is a known value As discussed in connection with the tongs control system 29 in Figure 6, the lift is stopped, the sensor is retracted, and the backup tong 1007 is locked.

Due to the standardization of drill pipes in the oil drilling industry, detection of a predetermined location such as a predetermined diameter on the box end taper, insures that any other surface feature on the pipe, such as the joint itself, is then a predetermined known distance 1230 from the location which generated the deflection signal Thus, it is insured that the tongs is in the operating position, that the backup tong and the driven tong are vertically symmetrical with respect to a horizontal plane through the pipe joint and that the joint may be made-up or broken-out by the tongs.

With reference to Figure 9, shown are views of standard drill pipe stands having the commonly named portions thereof indicated as shown Each end of each pipe stand illustrated has a distended joint portion indicated on Figure 2 at reference numeral 56 One end of the stands includes a threaded male member while the opposite end thereof is an internally threaded female member Normally, the pipe stand is inserted into the drill string such that the male end of each stand is inserted into the bore before the female end thereof The male end of the next-to-be engaged stand is then connected by a power tongs to the protruding female member of the lastinserted stand.

At both the male and female ends of the stand, below the tool joint outer diameter, a taper portion known as the box end taper and the pin end taper, respectively, is provided on the female and male ends of the stands Depending upon whether an internal or external upset is provided, further tapering of the drill pipe stand may occur The basic difference between an internal and external upset pipe stand is illustrated in Figure 9 Basically, an internally upset pipe presents a constant outer diameter between each of the end tapers while an externally upset pipe exhibits an upset taper on the exterior of the pipe stand In order to accommodate either internally of externally pipe stands, the joint sensor 1025 embodying the teachings of this invention is operative to emit a signal when the roller 1208 and arm 1206 thereof comes into abutting contact with an is deflected by a predtermined location on the box end taper Of course, any predetermined location on the end taper sections, either on the internally or externally upset pipe stand, may be detected by a joint sensor 1025 embodying the teachings of this invention.

Claims

WHAT WE CLAIM IS:-

1 A tongs arrangement for making and breaking a joint between lengths of drill pipe comprising: tongs lifting and lowering means; means for controlling a lifting speed; a backup tong; a power driven tong; means 70 for generating an electrical signal to lift the backup and the power driven tong at a predetermined speed to a predetermined elevation; means for generating a first electrical feedback signal representative of the tongs 75 being disposed at said predetermined elevation; means responsive to said first feedback signal for generating an electrical signal to close and lock a backup tong when it is lifted to a predetermined elevation; means for 80 generating a second electrical feedback signal representative of the closure and locking of said backup tong; and means responsive to said second feedback signal for generating an electrical signal to drive a 85 power dnven tong when a backup tong is closed and locked.

2 A tongs arrangement according to claim I and further comprising: a tong motor for rotating the driven tong to effect 90 the make-up and break-out of a pipe joint between lengths of drill pipe; an enabling network resposive to a first electrical select sequence command signal for selectively enabling the generation of electrical signals 95 to effect the make-up or break-out of a joint between lengths of drill pipe; first output signals generating means operatively connected to the tong lifting and lowering means and responsive to a second electrical 100 raise tongs command signal for generating a first electrical lift-up output signal to lift the tongs from a first, storage, position to a second, predetermined operating position and for stopping upward motion of the tongs in 105 response to a first electrical feedback signal; a joint sensor extendable to a position in contact with one of the lengths of drill pipe in response to a third electrical extend sensor command signal and retractable in 110 response to the first electrical feedback signal for disposing the backup and the driven tong in the predetermined operative position respectively located below and above a joint between the lengths of drill 115 pipe; first electrical feedback signal generating means operatively connected to the joint sensor for generating a first electrical feedback signal representative of the disposition of the backup and driven tong being dis 120 posed in the predetermined operative location with respect to a joint between the lengths of drill pipe; second output signal generating means operatively connected to the joint sensor and responsive to the first 125 feedback signal for generating a second electrical backup output signal to close the backup tong in gripping engagement with one of the lengths of drill pipe; second electrical feedback signal generating means 130 1 592 943 operatively connected to the backup tong for generating a second electrical feedback signal representative of the closed condition of the backup tongs; third electrical feedback signal generating means operatively connected to the backup tong for generating a third electrical feedback signal representative of the open condition of the backup tongs; and, third and fourth electrical output signal generating means responsive to the first command signal, a fourth electrical start sequence command signal and to the second feedback signal for generating a third electrical tong make output signal or a fourth electrical tong break output signal to the tong motor to rotate the driven tong in a direction to effect the make-up or break-out of a joint between lengths of drill pipe.

3 A tongs arrangement according to claim 1 or 2 wherein the tongs lifting and lowering means displace the tongs past a standby reference position intermediate to the lower and operating positions and further comprising; fourth electrical feedback signal generating means for generating a fourth feedback signal representative of the location of the tongs at least at the standby reference position.

4 A tongs arrangement according to claim 1, 2 or 3 wherein the tongs lifting and lowering means includes an arragement for controlling lift speed, the tongs being movable from the storage to the standby position at a first predetermined speed, and further comprising: fifth electrical output signal generating means responsive to the first output signal generating means and to the fourth feedback signal to generate a fifth electrical lift speed output signal to shift the speed at which the tongs are moved from the standby to the operating position from the first predetermined speed to a second, slower, speed.

A tongs arrangement according to claim 1, 2 or 3 further comprising: third electrical command signal generating means responsive to the fourth electrical output signal generating means and the fourth feedback signal for generating the third electrical extend sensor command signal to extend the joint sensor only when the tongs are being lifted and the tongs have passed the standby position.

6 A tongs arrangement according to any preceding claim wherein the first output signal generating means is responsive to the first feedback signal to half the motion of the tong lift.

7 A tongs arrangement according to claim 4 wherein the third electrical command signal generating means is responsive to the first feedback signal to retract the joint sensor.

8 A tongs arrangement according to any preceding claim including a stabber for guiding an upper length of drill pipe into a lower length of drill pipe and further comprising: fifth electrical command signal generating means responsive to the first feedback signal to generate a fifth extend 70 stabber electrical command signal to extend the stabber and responsive to the fourth electrical command signal to retract the stabber.

9 A tongs arrangement according to 75 claim 7 further comprising fifth electrical feedback signal generating means operatively connected to the stabber for generating a fifth electrical feedback signal representative of the extension of the stabber 80 A tongs arrangement according to any preceding claim wherein the joint sensor is responsive to the first feedback signal to retract the joint sensor and further comprising: sixth electrical feedback generating 85 means operatively connected to the joint sensor for generating a sixth electrical feedback signal representative of the retraction of the joint sensor and wherein the second output signal generating means generates 90 the second electrical backup output signal in response to the sixth feedback signal.

11 A tongs arrangement according to any preceding claim further comprising:

seventh electrical feedback signal generat 95 ing means operatively connected to the tongs motor for generating a seventh electrical feedback signal representative of a fully engaged joinder of the first and second lengths of drill pipe to stop rotation of the 100 tong motor; and, timing means operatively connected to the tong motor and responsive to the seventh feedback signal for generating the fourth electrical tong break output signal to reverse the tong motor to open the 105 driven tong and also responsive to the seventh feedback signal for opening the backup tong.

12 A tongs arrangement according to any preceding claim further comprising sixth 110 electrical output signal generating means operatively connected to the tongs lifting and lowering means and responsive to the third feedback signal for generating a sixth electrical lift down output signal to lower 115 the tongs to the first, storage, position.

13 A tongs arrangement according to any preceding claim further comprising:

backup closed memory means responsive to the first electrical lift up output signal and 120 the second feed back signal for generating a first electrical enabling signal; joint sensed memory means responsive to the first electrical lift-up output signal and to the first feedback signal for generating a second 125 electrical enabling signal; and, logic means operatively connected to the second output signal generating means and responsive to the third feedback signal and the first and second enabling signals for permitting open 130 1 592 943 ing of the backup tong only when the backup has been closed and the joint has been sensed.

14 A tongs arrangement according to any preceding claim wherein the first, second and fourth command signals are output to the tongs control system by a general purpose programmable digital computer operating under the control of a program.

15 A tongs arrangement for making and breaking joints between lengths of drill pipe substantially as hereinbefore described with reference to the accompanying drawings.

FORRESTER, KETLEY & CO, Chartered Patent Agents, Forrester House, 52 Bounds Green Road, London N 11 2 EY.

and also at Rutland House, 148 Edmund St, Birmingham B 3 2 LD.

-andScottish Provident Building, 29 St Vincent Place, Glasgow G 1 2 DT.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A 1 l AY, from which copies may be obtained.